Spinach Variety Trials and Planting Plan

Avon spinach in our hoophouse October 25.
Photo Pam Dawling

For years we grew only Tyee savoyed spinach. It did very well for us in central Virginia. It survived our zone 7a winters outside under rowcover. It could survive without the rowcover, but given that spinach makes growth whenever the air temperature is above 40F, and that the air under rowcover reaches that a lot more often then the air outside, we got much more growth using rowcover. We also got much better quality leaves, as they didn’t get battered by the weather.

Tyee is bolt-tolerant too but tended to yellow, slightly tough, leaves in the fall.

Tyee was dropped as a variety by the growers because (as I understand it) it suffered from a disease that is prevalent in the Pacific Northwest, where spinach seed is grown. It’s a hybrid, so we can’t just save our own seeds. We set out to try other varieties in order to find something to replace our beloved Tyee.

I wrote about spinach varieties here  in October 2016.

We tried Chevelle and Avon. Chevelle didn’t do that well for us. Part of the problem was poor germination, which could have just been that one packet of seed. But the pressure was on to find a productive variety, so we gave up on Chevelle.

We strongly prefer savoyed spinach over flat leaf spinach, because it has more loft in salad mixes and is more wilt-resistant after harvest. Apparently the East coast prefers savoyed spinach and the West coast the flat leaf kind, for what that’s worth. And of course, that takes no account of the millions of people between the coasts!

Reflect spinach from a September 12 sowing, outdoors under rowcover after the -9F night in early January.
Photo Pam Dawling

Next we tried Avon and Reflect, and they seemed pretty similar, both have good flavor.

Avon (42 days mature, 20 to baby leaf) semi-savoyed F-1 hybrid with upright growth, https://www.fedcoseeds.com/seeds/search?item=2538. Fedco likes Avon as a replacement for Tyee, but cautions

“We found Avon’s DM [Downy Mildew] resistance is not adapted to overwintered protected culture. Otherwise resistant to DM1,2 and CMV [Cucumber Mosaic Virus].”

Sounds like it might not do as well if water supplies run short once it gets hot. Bolting is initiated by heat, crowding and day-length over 14 hours. Avon claims strong bolt resistance.

Reflect (38 days to mature) semi-savoyed hybrid is recommended by Johnnys as a good alternative to Tyee. It has much more resistatnce to various Downy Mildew strains (1-11, 13, 15, 16), but is “slightly” faster bolting than Tyee. This factor could be set against its very fast growing rate. Its color is a medium-green, less dark than some other varieties.

This winter and spring we are trying Avon, Reflect, Renegade, Escalade and Acadia.

Renegade (43 days mature) smooth leaf hybrid. Slower growing than Corvair, which it resembles in flavor. Does well in chilly damp conditions (our winter hoophouse?) Has resistance to DM 1-7. Bolt-resistant, dark green leaves.

Escalade (43 days mature) slightly savoyed hybrid, with upright growth, claims high bolt resistance. Resistant to DM 1-14, 16. Slower growing than some. Expected to handle temperature and light variability. Good for baby leaf production (not what we do). The flavor is mild (not a good thing, for those of us who love spinach!) Will it grow fast enough in our short springs to give high yields before it bolts? We’ll let you know.

Acadia (45 days mature) slightly savoyed hybrid with upright growth. Resistant to DM 1-13, 15, 16. Even slower growing than Escalade, even more suited to baby leaf production

Our second sowing of hoophouse spinach. Left row Avon, then Acadia, then Escalade, with Renegade nearest the plastic. Sowed 11/8, photographed 2/5.
Photo Pam Dawling

Paul and Sandy Arnold in Argyle, New York, made a great slide show reviewing  Spinach Varieties in High Tunnels

The winners (in order) in terms of yield were Pigeon, Space, Giant Winter, Tyee, Palco. These were followed, after a noticeable drop in yield, by Raccoon, Renegade, Donkey, then another noticeable drop to Corvair, Regiment, and a plummet to Bloomsdale Longstanding and Samish. Giant Winter and Bloomsdale Longstanding are the only OPs in the list. We grew Giant Winter once. It did grow enormous leaves, but was very quick to bolt. Unsuited to repeated harvests in our climate.

In 2011-2012, High Mowing Seeds in northern Vermont did a spinach variety trial with 24 varieties, assessing productivity, color and harvest time. The 24 varied a lot in earliness, upright growth habit or not, flat or savoyed leaves, and level of pest resistance.

On color, America, Corvair, Crocodile, Donkey, Emilia, Lazio, Menorca, Queen, Raccoon, Red Kitten, Regiment, Samish, Seven Green, Space, Spargo, St Helens and Tyee scored 7 out of ten or better. Tyee only scored 7, Reflect only 4-5. The best were Corvair and Crocodile.

  • Corvair had a good color and upright growth (clean leaves, easy to pick).
  • Donkey was dark and productive.
  • Emu was an early producer with a better color,
  • Giant Winter was a great early producer although poor on color (and terrible on bolt-resistant when we grew it in Virginia).
  • Lombardia was good on yield and flavor,
  • Raccoon was one of the easiest to pick,
  • Red Kitten (red stems) was pretty and heavy but not high yielding,
  • Reflect was a good survivor in heavy rains,
  • Regiment gave high yields and had a good green color.
  • Space was one of the highest for yield,
  • Samish was good on yield and OK to pick,
  • Tyee had good savoy-ness but lower yield, although many other good points.

Our first sowing of spinach in the hoophouse, photographed in late September. Reflect on the left, Avon on the right.
Photo Pam Dawling

Here’s our spinach planting plan:

We are able to keep harvesting spinach from October 15 to May 25, all the way through the winter.

September 6 is our first sowing (sprouted seeds) in the hoophouse for winter harvest 10/30-2/15,

We sow outdoors on September 7 (sprouted seeds) for growing under rowcover and harvesting in fall and winter,

September 18-20 we sow in our coldframes and outdoors for harvest in early spring, until late May,

October 24 we make our second hoophouse sowing, to feed us November 25 to May 7. In 2017, we failed to water this planting enough, and had to resow November 8.

November 9  we make a third hoophouse sowing, intending to use these plants to fill gaps in our hoophouse as other winter crops come to an end.

January 16 we make more sowings in the hoophouse, some to continue to fill gaps there along the edges of the beds where they won’t fight with the tomatoes and so on, which we transplant starting March 15.

Most of the spinach sown this date is for transplanting outdoors February 21.

January 29 we sow in flats in the greenhouse if we see we haven’t got enough bare-root transplants in the hoophouse.

If we don’t have enough transplants, then on February 10 we sow outdoors with rowcover, for spring harvests until May 25 if we’re lucky. We have backup plans on backup plans for this!

In the hoophouse we continue transplanting spinach to fill gaps until March 31.

Hoophouse spinach #2. Front row (bottom of the picture) Acadia then Escalade then Renegade.
Photo Pam Dawling


Winter-Kill Temperatures of Cold-Hardy Vegetables 2018

Here’s the long version of one of the slideshows I presented on January 13 at the Future Harvest CASA conference. Since I got home, I updated my Winter-Kill Temperatures list, which appears in the slideshow. Compared to my list for 2016, there are a few differences, nothing major. We had some extremely cold weather, as I reported last week with some sorry pictures of lettuces. Now I have some photos of the outdoor crops too. The Vates kale had mixed survival, the rowcovered Reflect and Avon spinach are damaged but OK, the Tadorna leeks are battered but hanging in there (so are we!).

Vates kale which survived temperatures of -8F and -9F outdoors, uncovered.
Photo Pam Dawling

Vates kale with a freeze-killed center January 19 2018.
Photo Pam Dawling

For several years I have been keeping records of how well our crops do in the colder season. I note each increasingly cold minimum temperature and when the various crops die of cold, to fine tune our planting for next year. We had some extremely cold temperatures of -8°F and -9°F (-22°C and -23°C) in early January 2018. We are in zone 7a, with an average annual minimum temperature of 0-5°F (-18°C to -15°C).

Unless otherwise stated, these are killing temperatures of crops outdoors without any rowcover. All greens do a lot better with protection against cold drying winds. Note that repeated cold temperatures can kill crops that can survive a single dip to a low temperature, and that cold winds, or cold wet weather can destroy plants quicker than simple cold. Your own experience with your soils, micro-climates and rain levels may lead you to use different temperatures in your crop planning.

Hoophouse Notes

Our double-skin hoophouse keeps night time temperatures about 8F (4.5C) degrees warmer than outdoors, sometimes 10F (5.5C) warmer. Plus, plants tolerate lower temperatures inside a hoophouse. The soil stays warmer and the plants recover in the warmer daytime conditions (it seems to be the night+day average temperature that counts).

In the hoophouse (8F warmer than outside) plants without extra rowcover can survive 14F colder than they could survive outside; 21F colder than outside with rowcover (1.25oz Typar/Xavan).

For example, salad greens in a hoophouse can survive nights with outdoor lows of 14°F (-10°C) without inner rowcover. Lettuce, mizuna, turnips, Russian kales, Senposai, Tyee spinach, tatsoi, Yukina Savoy survived a hoophouse temperature of 10.4°F (-12°C) without rowcover, -2.2°F (-19°C) with. Bright Lights chard got frozen leaf stems.

Lettuce hardy enough for a solar heated winter hoophouse in zone 7a (hardiest are in bold): Buckley, Ezrilla, Green Forest, Green Star, Hampton, Hyper Red Rumpled Wave, Marvel of Four Seasons, Merlot, New Red Fire, North Pole bibb, Outredgeous, Pirat, Red Cross bibb, Red Sails, Red Salad Bowl, Red Tinged Winter, Revolution, Rouge d’Hiver, Salad Bowl, Sylvesta bibb, Tango, Winter Marvel, Winter Wonderland.

35°F (2°C):  Basil.

32°F (0°C):  Bush beans, cauliflower curds, corn, cowpeas, cucumbers, eggplant, limas, melons, okra, some Pak Choy, peanuts, peppers, potato vines, squash vines, sweet potato vines, tomatoes.

27°F (-3°C): Many cabbage varieties, Sugarloaf chicory (takes only light frosts).

25°F (-4°C): Some cabbage, chervil, chicory roots for chicons, and hearts, Chinese Napa cabbage (Blues), dill (Fernleaf), endive (Escarole more frost-hardy than Frisée), some fava beans (Windsor), annual fennel, some mustards (Red Giant, Southern Curled) and Asian greens (Maruba Santoh, Mizuna, most Pak Choy, Tokyo Bekana), onion scallions (some are much more hardy), radicchio.

Spinach under rowcover, with our hoophouse in the background – crop protection pays!
Photo Pam Dawling

22°F (-6°C): Some arugula (some varieties are hardier), Bright Lights chard, large leaves of lettuce (protected hearts and small plants will survive colder temperatures), rhubarb stems and leaves.

20°F (-7°C): Some beets (Bulls Blood, Chioggia,), broccoli heads (maybe OK to 15F), Brussels sprouts, some cabbages (the insides may still be good even if the outer leaves are damaged), celeriac, celtuce (stem lettuce), some head lettuce, some mustards/Asian greens (Tendergreen, Tyfon Holland greens), flat leaf parsley, radishes (Cherry Belle), most turnips (Noir d’Hiver is the most cold-tolerant variety).

Large oat plants will get serious cold damage. Oats seedlings die at 17°F (-8°C)

Canadian (spring) field peas are hardy to 10-20°F (-12 to -7°C).

15°F (-9.5°C): Some beets (Albina Verduna, Lutz Winterkeeper), beet leaves, some broccoli, some cabbage (Kaitlin, Tribute), covered celery (Ventura), red chard, cilantro, endive, fava beans (Aquadulce Claudia), Red Russian and White Russian kales, kohlrabi, some lettuce, especially medium-sized plants with 4-10 leaves (Marvel of Four Seasons, Olga, Rouge d’hiver, Tango, Winter Density), curly leaf parsley, rutabagas (American Purple Top Yellow, Laurentian) if not covered, broad leaf sorrel, most covered turnips, winter cress.

12°F (-11°C): Some beets (Cylindra,), some broccoli, Brussels sprouts, some cabbage (January King, Savoy types), carrots (Danvers, Oxheart), most collards, some fava beans (mostly cover crop varieties), garlic tops if fairly large, most fall or summer varieties of leeks (Lincoln, King Richard), large tops of potato onions, covered rutabagas, Senposai leaves (the core of the plant may survive 10°F/-12°C), some turnips (Purple Top).

10°F (-12°C): Covered beets, Purple Sprouting broccoli for spring harvest, a few cabbages (Deadon), chard (green chard is hardier than multi-colored types), some collards (Morris Heading can survive at least one night at 10F), Belle Isle upland cress, some endive (Perfect, President), young Bronze fennel, probably Komatsuna, some leeks (American Flag, Jaune du Poiteau), some covered lettuce (Pirat, Red Salad Bowl, Salad Bowl, Sylvesta, Winter Marvel), covered winter radish (Daikon, China Rose, Shunkyo Semi-Long survive 10°F/-12°C), large leaves of savoyed spinach (more hardy than flat leafed varieties), Tatsoi, Yukina Savoy.

Oats cover crop of a medium size die around 10°F (-12°C). Large oat plants will die completely at 6°F (-17°C) or even milder than that.

5°F (-15°C): Garlic tops even if small, some kale (Winterbor, Westland Winter), some leeks (Bulgarian Giant, Laura), some bulb onions, potato onions and other multiplier onions, smaller leaves of savoyed spinach and broad leaf sorrel. Many of the Even’Star Ice Bred greens varieties are hardy down to 6°F (-14°C), a few unprotected lettuces if small (Winter Marvel, Tango, North Pole, Green Forest).

Tadorna leeks, struggling but not dead, after -9F.
Photo Pam Dawling

0°F (-18°C): Chives, some collards (Blue Max, Winner), corn salad (mache), garlic, horseradish, Jerusalem artichokes, a few leeks (Alaska, Durabel, Tadorna); some bulb onions, yellow potato onions, some onion scallions, (Evergreen Winter Hardy White, White Lisbon), parsnips (probably even colder), salad burnet, salsify (?), some spinach (Bloomsdale Savoy, Olympia, Tyee). Walla Walla onions sown in late summer are said to be hardy down to -10°F (-23°C), but I don’t trust below 0°F (-18°C)

Crimson clover is hardy down to 0°F (-18°C) or slightly colder

-5°F (-19°C): Leaves of overwintering varieties of cauliflower die, Vates kale survives although some leaves may be too damaged to use.

Reflect spinach in the open got damaged but not killed at -9F.
Photo Pam Dawling

-10°F (-23°C) Austrian Winter Field Peas and Crimson clover (used as cover crops).

-15°F (-26°C) Hairy vetch cover crop – some say down to -30°F (-34°C)

-20°F (-29°C) Dutch White clover cover crops – or even -30°F (-34°C)

-30°F to -40°F (-34°C to -40°C): Narrow leaf sorrel, Claytonia and some cabbage are said to be hardy in zone 3

-40°F (-40°C) Winter wheat and winter rye (cover crops).

A cover crop of winter wheat untroubled by -9F.
Photo Pam Dawling

Book Review, The Bio-integrated Farm by Shawn Jadrnicek

Publisher: Chelsea Green. ISBN: 9781603585880

This book, by Shawn and Stephanie Jadrnicek, was hidden in my “to read” pile for too long! The title doesn’t make it clear enough that this is an authoritative text on all kinds of water management on the farm: integrating ponds, swales, ditches, water catchment, heat storage in water, irrigation, water for light reflection in winter, fish and shrimp-farming. Chickens and black soldier flies, compost-making and vegetable production in hoophouses and outdoors are all part of the bigger picture.

This book speaks from Shawn Jadrnicek’s experience at the Clemson University Student Organic Farm in South Carolina, and at his own homestead. The author tells us honestly when things he tried didn’t work out, and why. It is a permaculture book written for non-believers as well as the converted. It does not mystify with strange jargon. It does not make unsubstantiated claims about how things ought to be. Full disclosure: I suffer from having read too much permaculture writing that was obscure, convoluted, not backed with direct experience and written for people with a lot of time and only a small piece of land. This book is a breath of fresh air! The ideas have been tested on a farm scale, with a close eye on efficiency. It’s written for market farmers, homesteaders and serious gardeners, showing how to make best use of natural resources to help feed the world. Each technique has to have at least seven functions to qualify for inclusion in the author’s farming practices and the book.

You may not want to follow all of the author’s methods. I, for one, am not going to grow hydroponically. (I doubt that fully nutritious food can be grown without soil, with just the nutrients we know to feed in.) You may not want a hoophouse that is almost all pond. But you may be very happy to find a book that describes how to build a hoophouse on sloping land; very happy to learn how to grade your land to move rainwater away from where you don’t want it to sit, to where you do want it to improve growth of your pastures. You may be very happy to learn how to use a pond to grow minnows (tadpoles in the non-minnow season) to feed chickens. You may like the idea of filling your hoophouse with sweet potatoes or cowpeas in summer to act as a “smother crop,” dealing with weeds while keeping the soil alive. Perhaps you’d like to try freshwater prawn (large shrimp) farming? The regulations are easier than for fish-farming. Giant river prawns can weigh as much as a pound, they are easy to process and cook, and they sell at a good price.

Water management fills over half of the book, complemented by 30 pages on chickens, 33 on compost, 13 on fly farming, 28 on field layout and drainage, and 56 pages of case studies. Most of the vegetable production mentioned takes place in hoophouses (high tunnels). The book includes various ideas for heating the indoor crops, using hydronics (indirect heating with water in pipes warmed in outdoor ponds or compost piles), indoor ponds with solar pool covers, and compost piles leaning on the sidewall of the hoophouse. The information on rainwater harvesting includes checking your roofing material for toxicity (there is a special coating you can put on if necessary), how to avoid leaves clogging gutters (cleverly designed downspout filters), regulations about harvested rainwater, how to make gravity flow toilets and gravity drip irrigation systems that really work, and how to find the data and do the calculations. The level of detail in this book inspires confidence!

The chicken-farming system in this book uses a permanent coop and alley (mulched corridor) along with temporary pens made with electric netting. This makes better use of resources than free-ranging, unless you have only mature trees and grass. The birds get 30% of their dietary needs from the landscape, if rotated every 6-12 days onto perennial clover and grass pasture that has regrown to 4-8″ in height. This system ensures the chickens can always reach shade, and you can reseed bare spots in the resting pens with rye, wheat, millet, sunflowers and buckwheat, and reduce their feed costs by 30%. I liked the careful thinking and observation behind this scheme.

And then we come to the black soldier flies. The mesh flooring of the chicken pen lets the manure fall through into a fly digester below. The fly larvae digest the manure and grow, later becoming chicken food themselves. I wasn’t initially attracted to the idea of deliberately breeding flies, but the system has a lot going for it. Black soldier flies (Hermetia illucens) are not a pest. In fact they out-compete houseflies and thus reduce their numbers 95%! The adult soldier flies live only 5-15 days – they have no functioning mouthparts, and they don’t vector diseases. They are native in zone 7 and warmer, especially in the Southeast, so consult your Extension Service to find out if you’ll need to mail order them or just set out a nice digester once it’s warm enough. This sounds better than worm-bin farming! The flies tolerate a wider range of conditions and consume waste faster than earthworms. The large segmented larvae will “self-harvest” into buckets, if you have a well-designed digester. Two commercial models are available, the larger ProtaPod (4 ft diameter) and the smaller BioPod. They have internal ramps that the pre-pupae will climb, and a curled rim that prevents escape. The creatures launch themselves down a tube into a lidded bucket. All the details are in the book! Add fresh waste daily, and empty the bucket at least weekly (to prevent adult flies hatching out and setting up residence where you don’t want them).

The section on compost-making includes how to extract heat from your compost pile to warm your hoophouse, and how not to extract so much heat that the compost stops working. My beef with some other books about methods of heating greenhouses is that they fail to address the unintended side-effects, such as having very humid air go into your living space, or having little space left to grow plants because the greenhouse is full of heat-storing devices. Make good compost, and warm your hoophouse a bit.

The section on field application of these ideas is not about growing vegetables, but about field layout and drainage. It includes useful calculations on using drip irrigation. It also discusses keyline plowing, which had previously been just a bit of permaculture theory to me. Shawn says, “keyline pattern cultivating intrigued me for years, but I first had to implement the technique before becoming a convert.” There is no need to buy the special equipment some advocates suggest, if you have a box scraper with ripping tines. Keyline plowing (ripping 4″ deep in lines through pasture or grassways to direct water from a valley to a bit of a ridge) helps build soil and increase grass growth. Reading Shawn’s results, I now understand why others said it was a good idea.

I recommend this book to any small-scale farmers who are interested in learning efficient techniques to increase productivity while reducing use of resources.

Stephanie and Shawn Jadrnicek
Photo Chelsea Green

Garden Planning, Winter Harvests and Speaking Events

Garden Planning Field Manual
Photo VABF

‘Tis the season – after the relaxation of the holidays – time for garden planning. Inventory your seeds left from last year, peruse the catalogs and prepare your seed orders. The earlier you get them in, the more likely you are to get the varieties you want, before anything is sold out.

I notice that readers of my blog have been looking up the Twin Oaks Garden Calendar,  also known as The Complete Twin Oaks Garden Task List Month-by-Month. You can search the category Garden Task List for the Month, or you can click on the linked name of the month you want. At the end you can click on “Bookmark the Permalink” if you might want to refer to this in future. Remember, we’re in central Virginia, winter-hardiness zone 7a. Adjust for your own climate.

Meanwhile, despite the turn to cold weather, we are not huddled indoors all the time. Each day, one or two of us sally forth to harvest enough vegetables to feed the hundred people here at Twin Oaks Community. Outdoors, in the raised bed area, we have winter leeks, Vates kale, spinach and senposai. We could have had collards but we lost the seeds during the sowing period, so we have lots of senposai instead. Senposai leaves (the core of the plant may survive 10F), are hardy down to about 12F. I noticed some got a bit droopy when we had a night at 15F. Collards  are hardier – Morris Heading (the variety we grow) can survive at least one night at 10F.

Hoophouse December View
Photo Kathleen Slattery

In the hoophouse, we have many crops to choose from: lettuce, radishes, spinach, tatsoi, Yukina Savoy, Tokyo Bekana, turnips and turnip greens, scallions, mizuna, chard, Bull’s Blood beet greens.

Hoophouse scallions ready to harvest.
Photo Pam Dawling

Pak Choy and Chinese cabbage heads are filling out, ready for harvest in January.

Tokyo Bekana, a non-heading Asian green,  has large tender leaves, which we are adding to salad mixes. It can be used as a cooking green, but only needs very light cooking. It will bolt soon, so we are harvesting that vigorously, not trying to save it for later.

The kale and senposai in the hoophouse are being saved for when their outdoor counterparts are inaccessible due to bad weather. The spinach is added to salad mixes, or harvested for cooking when outdoors is too unpleasant, or growth slows down too much.

Hoophouse winter lettuce: Green Forest and Red Salad Bowl, two of our fifteen varieties.
Photo Wren Vile

Another kind of planning I’m doing right now is scheduling my speaking events for the coming year and practicing my presentations. Last week I updated my Events page, and this week I’m adding a new event: The September 21-22 Heritage Harvest Festival.

I might pick up a couple of events in late April and early June, but that’s just speculation at this point.

Right now I need to practice for the CASA Future Harvest Conference January 11-13. Cold-hardy Winter Vegetables and a 10-minute “Lightning Session” on using graphs to plan succession plantings for continuous harvest. Click the link or my Events page for more on this.

What Makes Potatoes Sprout?

Harvesting potatoes. Photo Lori Katz

“White” or Peruvian potatoes (sometimes called Irish potatoes) are stem tubers in the nightshade family; sweet potatoes are root tubers in the Morning Glory family. This article is about Peruvian potatoes, not sweet potatoes.

Curing potatoes

Potatoes are cured enough for storage when the skins don’t rub off. It’s best to leave the potatoes in the ground for two weeks after the tops die, whether naturally or because of mowing, if you want them to store. When the potatoes are harvested after the skins have toughened, there will be less damage during harvest. Curing allows skins to harden and some of the starches to convert to sugars. These changes help the tubers to store for months.

When potatoes first go into storage, they are still “alive” and respiring, and need fresh air frequently. They will heat up if left closed in, and could develop black centers, where the cells die from lack of oxygen.

Storing newly harvested potatoes

For the first two weeks after harvest, the root cellar or other storage space will need 6-9 hours of ventilation every two or three days. The temperature goal is 60°F–75°F (16°C–24°C), with 95% humidity. Ventilate when the temperature is 0–20F (0–11C) cooler than your goal: in the daytime if nights are too cold and days are mild; at night if nights are mild and days too warm. If it is very damp in there, ventilate more.

Two weeks after harvest, sort all the potatoes. By this time, any which are going to rot have likely started doing so. Restack, remembering to keep airspace between the crates and walls. For weeks 2–4, the temperature goal is 50°F (10°C) and fresh air is needed about once a week.

Potato crates in our root cellar.
Photo Nina Gentle

Long term potato storage

After week 4 in winter, cool to 40°F (5°C); in summer, below 50°F (10°C). Ventilation for air exchange is no longer needed, as the tubers have become dormant. The final long-term storage conditions are cool and fairly moist, 40°F–50°F (5°C–10°C), 85%–90% humidity—a  root cellar is ideal. Below 40°F (5°C) some starches convert to sugars, giving the potatoes a bad flavor and causing them to blacken if fried. Try hard to avoid having the cellar cool down, then warm up. That causes the potatoes to sprout.

Pre-sprouting seed potatoes

Potatoes have a dormant period of 4–8 weeks after harvest before they will sprout. The warmer the conditions after dormancy ends, the quicker they will sprout. If you want potatoes to sprout during the dormant period, trick them by refrigerating for 16 days, then pre-sprouting them in the light.

We routinely “chit” or pre-sprout our seed potatoes before planting. Bring the seed potatoes into a warm, well-lit room around 65°F–70°F (18°C–21°C) and set them upright in shallow boxes, rose end up, stem (belly-button) down, for 2–4 weeks in spring, 1–2 weeks in summer. For summer planting, store your seed potatoes in a cool place at 45°F–50°F (7°C–10°C) until 2 weeks before your planting date, then sprout them.

Seed potato pieces after pre-sprouting for planting.
Photo Kati Falger

The effects of ethylene

Ethylene is a naturally occurring, odorless, colorless gas produced by many fruits and vegetables, but it can also be produced by faulty heating units and combustion engines. Propane heaters should not be used, as propane combustion produces ethylene. Incomplete combustion of organic fuels can result in the production of carbon monoxide, ethylene and other byproducts. Do not use any unvented hydrocarbon fuel heaters near stored produce.

Ethylene is associated with ripening, sprouting and rotting. Some crops produce ethylene in storage—apples, cantaloupes, ripening tomatoes, already-sprouting potatoes all produce higher than average amounts. Chilling, wounding and pathogen attack can all induce ethylene formation in damaged crops.

Some crops, including most cut greens, are not sensitive to ethylene and can be stored in the same space as ethylene-producing crops. Other crops are very sensitive and will deteriorate in a high-ethylene environment. Potatoes will sprout, ripe fruits will go over the top, carrots lose their sweetness and become bitter.

Summary: Potatoes are more likely to sprout if they are more than 4–8 weeks after harvest; in the light; near fruits, vegetables, flowers or malfunctioning propane or natural gas heaters that produce ethylene; too warm, or warm after being cool.  Potato sprouts are toxic, see my earlier article.

Planting potatoes.
Photo Wren Vile

What Makes Sweet Potatoes Sprout?

Sweet potatoes crated in the field.
Photo Nina Gentle

The difference between Peruvian (“white”) potatoes and sweet potatoes

Peruvian potatoes (sometimes mistakenly called Irish potatoes) are stem tubers in the nightshade family; sweet potatoes are root tubers in the Morning Glory family. Stem tubers have buds, nodes and internodes, and scaly leaves, and the ability to develop chlorophyll when exposed to light. Root tubers do not have these attributes. This article is only about sweet potatoes.

The difference between curing and storage

Some vegetables need to cure before storage and the curing conditions are different from those needed for storage. Curing allows skins to harden and some of the starches to convert to sugars. These changes help the tubers to store for months.

Curing sweet potatoes

Within an hour or two after harvest, field drying, sorting and crating, take the boxes of sweet potatoes to a warm, damp indoor space to cure. Curing allows the skin to thicken, cuts to heal, and some of the starches to convert to sugars. Uncured sweet potatoes are not very sweet, will not bake well, and are best used in dishes with other foods.

In addition to promoting the healing of wounds acquired during harvesting and handling, the curing conditions are necessary for development of a protective cork layer over the whole root. And a waxy material (suberin) is produced by the root’s outer cells and covers the skin. This layer acts as a barrier to disease organisms, and prevents excess moisture loss.

Boxes of sweet potatoes curing.
Photo Nina Gentle

Curing involves optimizing three conditions: temperature, relative humidity and ventilation. Ideal curing conditions are 85°F–90°F (29°C–32°C), and 80–95% humidity for 4–7 days. Curing takes longer (as much as 3 weeks) if conditions are less than perfect. Dry air does not lead to good curing. If the air is below 66% humidity, timely good healing will not take place, and the sweet potatoes will not store well unless more time is allowed. The loss from decay in sweet potatoes cured at 50% is twice that of those cured at 82%. (Storage of sweetpotatoes, Jacob Martin Lutz, USDA, 1958)

In the past we used our greenhouse to cure sweet potatoes, but it really is too hot and sunny, and dry. Nowadays we use a heated basement. We stack our 4” (10cm) deep boxes of roots on pallets, with wood spacer bars between boxes in each stack, to ensure air flow. We use box fans to improve the airflow, and the basement already has some natural ventilation. We reckon on 10–14 days.

We get quite good temperatures, but keeping humidity up is difficult for us. We cover the flats with newspaper to hold in some moisture. Some people use perforated plastic. We have also used domestic humidifiers and we’ve tried hanging strips of wet cloth from the ceiling. The best result seems to come from splashing water on the concrete floor several times each day.

To test if curing is complete, rub two sweet potatoes together. If the skins scratch, they need to cure longer. Curing longer than needed leads to sprouting.

Sweet potato storage

Sweet potatoes can be stored in the same room they are cured in, but it is important to cool the room evenly and fairly rapidly from the curing temperature of 85°F–90°F (29°C–32°C),  to the storage temp of 55–60°F (13°C–16°C) in 10 days or fewer.

Above 60°F (16°C), shrinking, pithiness, and internal cork (a symptom of a viral disease) when the virus is present may occur, and below 55°F (13°C), a permanent chilling injury (Hard Core) can happen. The potatoes remain hard no matter how long you cook them, and are useless. Do not ever let the temperature drop below 50°F (10°C). Ideal storage conditions for sweet potatoes include 60–70% humidity, up to 85 %, with one air change each day. If the heat circulation is uneven, hot spots can develop in front of the heaters and cause severe losses. Never let hot air blow directly on the sweet potatoes. Do not store in airtight containers, sweet potatoes need one complete air change per day.

Ken Allan, in Sweet Potatoes for the Home Garden, informs us that at about 60°F (16°C), the metabolism of the sweet potato slows to near zero, meaning it won’t grow. Temperatures above 70°F (21°C) are conditions that allow growth: although slow at 70°F (21°C), the rate increases to fast at 100°F (38°C).

We use a rodent-proof “cage” in our basement. We stack the boxes directly on top of each other and this seems to keep enough moisture in. This way, assuming we had a good enough harvest, we can still have sweet potatoes into May and early June. Shrinkage occurs at 1–2 % per month if cured, 2–5 % if uncured. In some cultivars, pithiness also increases with length of storage.

Sweet potatoes do not need to be in the dark. Dormancy is generally broken by moisture and warmth, not daylight. Green sweet potato sprouts are edible, not toxic, as white potato sprouts are.

The effects of ethylene

Ethylene is a naturally occurring, odorless, colorless gas produced by many fruits and vegetables, but it can also be produced by faulty heating units and combustion engines. Propane heaters should not be used, as propane combustion produces ethylene. Incomplete combustion of organic fuels can result in the production of carbon monoxide, ethylene and other byproducts. Do not use any unvented hydrocarbon fuel heaters near stored produce.

Ethylene is associated with ripening, sprouting and rotting. Some crops produce ethylene in storage—apples, cantaloupes, ripening tomatoes all produce higher than average amounts. Chilling, wounding and pathogen attack can all induce ethylene formation in damaged crops.

Some crops, including most cut greens, are not sensitive to ethylene and can be stored in the same space as ethylene-producing crops. Other crops are very sensitive and will deteriorate in a high-ethylene environment. Potatoes will sprout, ripe fruits will go over the top, carrots lose their sweetness and become bitter. Sweet potatoes are sensitive to ethylene and should not be stored with any crops or any heating systems that produce ethylene. Symptoms are difficult to diagnose, but ethylene can cause internal darkening and pithy areas, as well as sprouting.

Accidental sprouting of sweet potatoes

If your curing or storage conditions were not right, you may get early sprouting. If this happens, snap off the sprouts and use the sweet potatoes as soon as possible. If the sweet potato also has soft and wrinkly flesh, it’s an indication that it has lost nutrients. Left longer, spouted sweet potatoes become mushy and turn brown or black.

Seed sweet potatoes growing slips.
Photo Kathryn Simmons

Intentional sprouting of sweet potatoes

Sweet potatoes that are intended for sprouting are kept under normal storage conditions, then conditioned for 2 weeks (or even 4), before you start to grow slips. Start 10–12 weeks before your planting date, conditioning at 75°F–85°F (24°C–29°C), 95% humidity for 2–4 weeks, then set to sprout. Set up a place with light, humidity and ventilation at 75°F–85°F (24°C–29°C) and 12″ (30 cm) of headroom.

Summary: Sweet potatoes are more likely to sprout if they were cured for too long; curing conditions were too far from ideal; temperatures stayed too high—above 60°F (16°C)—once the sweet potatoes were cured (especially at high humidity); they were exposed to low temperatures followed by higher ones; they were physically damaged or stored near ethylene sources.

Sweet potato harvest
Photo Nina Gentle

Soil tests and high phosphorus levels

I just got back from the Carolina Farm Stewardship Association Conference, where I had a great time. I will be posting my slideshow Sequential Planting of Cool Season Crops in a High Tunnel here next week, after I’ve added back in some of the material I had to cut to fit the time slot. Meanwhile here’s some in depth thoughts about phosphorus levels, an issue for those of us who pile lots of animal manure or compost on our gardens.

Soil pH analysis machine at Virginia Tech.
Photo from Virginia Tech

This is the best time to get a Soil Test

            Get an annual soil test in the fall, from the same agency each time—different labs sometimes use varying test methods. Also, soil collected in spring is usually higher in P than soil collected in the fall. Consult an agronomy book, your extension service, or a live agronomist for help in interpreting your test results. Most soil tests don’t include a measure of organic matter as this can vary a lot from week to week. My state extension service provides standard tests for soil pH, P, K, Ca, Mg, Zn, Mn, Cu, Fe, B, and estimated CEC, plus a fertilizer and lime recommendation. For a small fee there are special tests for soluble salts and organic matter.

Amendments and the Issue of High Phosphorus

High levels of soluble salts, including nitrate, potassium, and sulfate from fertilizers or organic materials like compost can build up and stunt plant growth.  Some of the salt problems are caused by having very high organic matter levels, due to heavy amendment with composts or manures. In high OM soils, when warm or when irrigated after a dry spell, large flushes of nitrate can occur. This makes it difficult to manage nitrogen levels.

Organic soil amendments include soil inoculants, organic mulches, biochar and other soil conditioners, lime and other natural minerals, manure and other organic fertilizers, such as alfalfa meal, soybean meal, fish meal, kelp, composted chicken litter and compost.

Screening compost from a huge pile, for spring seedling compost.
Photo Wren Vile

Most growers are lavish with compost when they can be. Good quality finished compost is a way to add organic matter and nutrients. Compost can add a range of beneficial bacteria and fungi, which can inoculate plants against diseases by inducing systemic acquired resistance. The plants produce antibodies and other protective compounds before any infection can occur. Compost improves the soil structure, organic matter and humus. The effects last longer than cover crops and crop residues, especially in humid conditions where the breakdown of plant material is very rapid.

How much compost is too much? Some of us were raised to think of compost as the gold standard soil improver, and find it hard to believe there can be too much of a good thing. Others may consider compost like salad dressing—something to add that je-ne-sais-quoi to a good meal.

Compared with poultry litter compost (lower C:N  ratio), on-farm mixed compost (high C:N) leads to higher total soil organic C and N, higher N mineralization potential and better water infiltration. Poultry litter compost can enhance organic matter and N mineralization potential over conventional systems, but can lead to excess P. In terms of organic matter, composted manure is better than uncomposted solid manure, and both add more than slurry manure (which provides very low C:N; and half of the N is ammonium).

Manure and compost can add too much P relative to N and K. It is worthwhile to understand the effect of phosphorus.

Phosphorus in the Soil and in Plants

Phosphorus is needed for cell division, hence to promote root formation and growth, vigorous seedlings, flowering, crop maturity and seed production, and to improve winter hardiness in fall plantings. Phosphorus is important in fat, carbon, hydrogen and oxygen metabolism, in respiration, and in photosynthesis. It is stored in seeds and fruit.

Phosphorus binds easily with many other minerals in the soil, forming compounds that are not very soluble in water, therefore most of the phosphate in soils exists in solid form and phosphorus does not move freely with soil water. Although P is very mobile within plants, it is relatively immobile in soil and does not leach readily in normal rainfall or irrigation.

P is most available to plants between soil pH of 6 and 7.5, especially pH 6.5-6.8.

In neutral and alkaline soils P is mostly present as insoluble calcium phosphates. In acid soils below pH 5.5, most of the P is bound as iron phosphate or aluminum phosphate, compounds that further change gradually into very insoluble compounds not available to plants. If a soil test shows a pH that is far from neutral, with a slightly low P level, correct the pH and repeat the soil test before amending the P level.

In the soil water, P is only present in very small amounts, but when removed by plants, supplies are quickly replenished from the “active P pool” (P in solid compounds which is relatively easily released to the soil solution). The “fixed P pool” contains inorganic phosphate compounds that are very insoluble, and organic compounds that are resistant to mineralization by microorganisms in the soil. Although some slow conversion between the fixed P pool and the active P pool does occur in the soil, phosphate may remain for years without being available to plants and may have very little impact on soil fertility.

Since the movement of phosphates in soils is very limited, roots have to grow to the phosphorus—it will not move towards the plants. Manure contains soluble phosphate, organic phosphate, and inorganic phosphate compounds that are quite available. Water-soluble forms generally become insoluble very soon after application to the soil.

Phosphorus Deficiency

In cold soils less P is available from organic materials, because biological activity is required to release it and it runs slow when it’s cold. Also, roots cannot absorb P well from cool soils.  Early spring brassicas can show red or purplish colors (anthocyanin pigment) in the leaves, especially undersides, and the lower stems. Cell necrosis may follow. Root growth will be poor, plants may exhibit stunting and delayed maturity. Tomato plants may have yellow leaves, with purpling on the underside of leaves. They may exhibit reduced flowering and delayed maturity. To avoid P deficiency problems, wait until the soil is 60°F (15.5°C) before planting.

Effects of excess soil salt levels on crop foliage.
Photo Rose Ogutu, Horticulture Specialist, Delaware State University

Excess Phosphorus

The main symptom of excessive phosphorus in soil is stunted plant growth. High P interferes with N absorption. Also there may be symptoms of deficiencies of zinc, iron, cobalt or calcium, because the P has locked up these nutrients.  Zn deficiency shows as bleaching of plant tissue, Fe deficiency as yellowing between leaf veins. Co is involved in the process by which the plant stem grows, shoot tips elongate, and leaves expand. Ca deficiency produces blossom end rot of tomatoes.

Phosphorus inhibits the growth of mycorrhizae which help the plant absorb water and nutrients. Increased growth of non-mycorrhizal weeds such as velvetleaf, lambsquarters, pigweed and galinsoga can be sign of excess P, explained Klaas Martens at MOFGA’s 2009 Spring Growth Conference.

Aside from plant growth problems, the issues with having very high P levels in your soil include that if it reaches waterways it can accelerate eutrophication—the nutrient enrichment of surface water leading to problem algal growth. When an algal bloom dies, it decomposes, using up the oxygen in the water, so fish and other organisms die too. Phosphorus is a paradoxical element in that it is an essential nutrient, is not toxic itself and has low solubility, but can have damaging effects on water quality at quite low concentrations.  Because P is usually locked up, leaching of soluble P from soils is not normally a problem, but if soil particles are carried to a river or lake, P is contained in this sediment.

Mitigating High Phosphorus Levels

Ear of triticale.
Photo triticale-infos.eu

The quickest way to reduce excess soil P (which can take years!) is to stop any manure or compost application while continuing to grow crops that can be eaten or sold. One solution for vegetable growers may be to grow cover crops as forage crops, and graze or bale grass crops to sell off the farm as livestock feed. For example, triticale is very good at removing P from the soil and producing winter forage. The P removed ranges from 7–36 pounds/acre (7.8–40 kg/ha). The more P your soil has, then the higher the P level in triticale grown in that soil. Double cropping can remove P at twice the rate.

Vegetable growers do not have the problem of P accumulation to such a big degree as livestock farmers, nor do vegetable crops remove P at the rate forages do. See the New England Vegetable Management Guide Removal of Nutrients from the Soil for a table of Approximate Nutrient Removal by Selected Vegetable Crops. The best vegetable removers of P are celery (80 lbs P2O5/acre, 90 kg/ha), tomatoes (72 lbs, 81 kg), potatoes (65 lbs, 73 kg), sweet potatoes (60 lbs, 67 kg), peppers (52 lbs, 58 kg, fruits only), cucumbers (33–72 lbs, 37–81 kg), eggplant (56 lbs, 63 kg). Onions remove about 25 lbs (28 kg/ha) one-quarter of the P removed by alfalfa hay (104 lbs, 117 kg) In all cases, to achieve results this high, grow high yields and remove the vines too, although you can’t sell those! Beans and peas are in the 7–10 lbs (8–11 kg) range if just pods, 20 lbs (22 kg) with vines. P2O5 is 43.7% P.

Celery, the star of phosphorus-removing vegetable crops.
Photo Kathryn Simmons

Strategies to reduce the amount of P added each year include adjusting your compost use rates according to soil test P results. On low-P soil, use at rates to meet the soil needs for N or K, which will  increase P levels. If the soil P is high or optimum, use compost sufficient to just replenish P, and legume cover crops (or legume food crops) to supplement N. For very high or excess soil P, only use compost sparingly as a micro-organism inoculant, rather than a fertilizer, and  if  test reports show more than 40 lbs P per acre (45 kg/ha), consider using only soil amendments containing little or no P. If phosphorus levels are excessive, avoid using manure composts (high in phosphorus), and other fertilizers and amendments containing phosphorus. Add more carbon (“brown”) ingredients to compost you make on-farm.


Sowing hoophouse winter crops

New spinach seedlings in our hoophouse.
Photo Pam Dawling

We are on our way with our late fall, winter and early spring crops in the hoophouse. On September 6 and 7 we sowed five crops in our first bed – spinach, tatsoi, Bulls Blood beet greens, radishes and scallions. On September 15 we sowed lettuces, chard, pak choy, Chinese cabbage, Tokyo Bekana and Yukina Savoy, in an outdoor bed to be transplanted into the hoophouse in a few weeks, after we’ve prepared another bed.

Broadfork from Way Cool Tools.
Photo Way Cool Tools

To prepare hoophouse beds for winter crops, we first remove the summer crops to the compost pile, then spread a generous layer of compost over the surface. We use about five wheelbarrowsful for one bed 4’ x 90’. Next we move the three lengths of drip tape off to one side or the other, and broadfork the whole area. We have an all-steel broadfork from Way Cool Tools that we really like. To use a broadfork, work backwards either going the length of the bed or the width. Stab the tines into the soil and step on the crossbar, holding the long handles. Step from foot to foot until the bar touches the soil, with the tines all the way in, then step off backwards, pulling the handles towards you. This loosens a big area of soil, which hopefully crumbles into chunks. Lift the broadfork and set it back in the soil about 6” back from the first bite. Step on the bar and repeat. We’ve found it’s important to only broadfork the amount of space you have time to rake immediately, otherwise the warm hoophouse conditions dry out the soil and make it harder to cultivate into a fine tilth, which is the next task. Sometimes we use a rake, breaking the clumps up with the back of the rake, then raking the soil to break up the smaller lumps, and reshape the bed.

7″ stirrup hoe.
Photo Johnnys Selected Seeds

Sometimes we use a wide stirrup hoe very energetically. This isn’t the job scuffle hoes were designed for (that’s very shallow hoeing, and hence why we call them scuffle hoes), but the sharp hoe blade does a good job of breaking up clumpy soil. We’ve also found it important to lay the drip tapes back in place in between each day’s work, so that the soil gets irrigated when we run the system and stays damp. We don’t want dead, baked soil.

Once the bed is prepared, we measure out the areas for different crops and mark them with flags. Next we use our row-marker rake (bed prep rake) from Johnny’s Selected Seeds.

Johnny’s Bed Prep rake with row marker pegs.
Photo Johnnys Selected Seeds

We plant crops closer in the hoophouse than outdoors, and closer to the edges of the beds. We don’t have many weeds in the hoophouse, and the paths are marked off with twine, to keep us from stepping on the beds, compacting the soil. We find that the soil does slump and compact some of its own accord, even if we don’t step on the edges (and of course, some feet do find themselves on the bed edges sometimes), hence the once-a-year broadforking. We found out how valuable the soil loosening is, because one year before we started broadforking, we decided to loosen the edges with a digging fork to make up for several years of accidental steps. The edge rows of spinach grew much bigger than the inner rows, and we realized that the whole bed needed loosening.

After the rowmarking, we deepen the furrows if needed (often it’s not needed), using a pointed hoe, then sow the seeds. We pre-sprout our spinach for a week in a jar in the fridge. Just soak the seed overnight, drain it in the morning, fit a mesh lid on the jar, and lay it on its side in the fridge. Once a day, give the jar a quarter turn to tumble the seeds and even out the moisture. This year the seeds were a bit wet when I came to sow them, and clumped together. I poured them out on a cloth to dry a bit before I sowed. This year we are growing two varieties (Avon and Reflect) side by side, still seeking a replacement for our much loved Tyee, which was pulled from the market, because it was prone to a disease prevalent in the West.

Easter Egg radish seedlings in our hoophouse.
Photo Pam Dawling

The spinach, tatsoi and radishes came up very quickly, with the beets a day or two behind. The scallions came up in a week, which is quicker than at other times of year.

One week after the sowings, I thinned the spinach and radishes to 1” apart in the row. We are growing Easter Egg, Cherry Belle and White Icicle radishes. The Cherry Belle will be ready first, Easter Egg next (they mature relatively gradually, giving us a nice harvest period). Icicle are unusual long white radishes which are slower to mature, and slow to get woody.

Buckley One-cut (Eazileaf) lettuce.
Photo High Mowing Seeds

Meanwhile, outdoors on September 15 we sowed the first half of the crops that we transplant bare-rooted into the hoophouse. Our planned schedule called for 10 varieties of lettuce, but I ended up sowing 12, partly because we are trying three new Vitalis one-cut lettuce varieties from High Mowing Seeds: Ezrilla, Hampton and Buckley.  These are bred to provide lots of similar-sized leaves from cutting. They can be cut and mixed for baby salad mix or cut as whole heads for easy-to-prepare salads, or harvested by the leaf (or layers of leaves) once the plant has grown to full size. This is how we use them. They were previously called Eazileaf varieties, and are now called One-cut lettuces. They are only available as pelleted seed, so I regard them as too pricey to grow for baby salad mix, and best used for multiple harvests.

Johnny’s Green Sweet Crisp Salanova lettuce.
Photo Johnnys Seeds

Osborne’s Multigreen 3 lettuce.
Photo Osborne Seeds

You can click here to read the New Head Lettuces article Andrew Mefferd wrote about this new type of lettuce in Growing for Market magazine. We have previously grown Johnny’s Salanova and Osborne’s Multileaf varieties and I wrote about them here and here. This year we are trying the High Mowing ones. We did a small trial of them outdoors in spring, knowing that in our climate (very different from High Mowing’s in Vermont) they might well bolt. They grew into handsome plants, but clearly they are more suited to fall than spring in our quickly-heating-up climate.

Other lettuces we sow for our winter hoophouse crops include Oscarde, Panisse, Tango which have a similar shape of lots of same-sized leaves, and Green Forest (romaine), Hyper Red Rumpled Wave, Merlot, Revolution, Salad Bowl and Red Salad Bowl. I would have sown Red Tinged Winter but we seem to be out of seed.

Red Salad Bowl lettuce.
Photo Bridget Aleshire

Hoophouse tomato varieties

Tall tomatoes with beans and cucumbers in our hoophouse.
Photo Wren Vile

Our hoophouse tomatoes are doing well this year. Apart from the determinate Glacier, they’ve reached the top of the stakes and as high as we can string-weave or pick. We transplanted them March 15, a month before our last frost date. We harvest each of our hoophouse beds every two days,alternating them to smooth supplies.We plan to harvest for ten weeks from May 25 till July 31, by which time our first outdoor planting is yielding well. In the South many of us grow only our early tomatoes in hoophouses, as outdoor crops produce abundantly once the weather warms. We harvest our outdoor tomatoes (sown 3/15) from July until frost, initially overlapping with our hoophouse earlies, then on their own.

Ken Dawson in Cedar Grove, NC, has a succession planting plan for outdoor tomatoes. He makes four field plantings at three week intervals. In cooler climates, because yields will be higher, it is more common to grow tomatoes in hoophouses whenever possible, and keep them growing for the whole season.

Glacier tomatoes in our hoophouse in late June.
Photo Pam Dawling

It is possible to grow successions of determinate tomatoes in a hoophouse, but any advantages are usually outweighed by the disadvantages of disease spread and the extra time plants spend before they reach production. In the past we grew a late hoophouse crop, to take us beyond the first frosts. We sowed June 18 and transplanted at a relatively young age (tomatoes grow quickly by that point of the year). We gave this up in favor of growing more leafy greens.

Each year I take notes on the varieties we have in the hoophouse, and often we run a taste test. I have also been gathering information from other growers, on which varieties do well for them. Before I get into talking about specific varieties, I want to say a bit about types of tomatoes.

Determinate Varieties

Varieties can be divided into two main growth types and then the exceptions. Determinates (bush tomatoes) are compact varieties that stop growing at a height of 2′-4′ (0.6-1.2 m). The number of stems, leaves and flowers is part of the genetic makeup of that variety. The number of leaves between one fruit cluster and the next decreases by one each time a cluster is produced, until the terminal cluster forms. No more leaves or flowers develop after that. The fruit ripens and the plant starts to die back. Harvest can be 1-3 months from start to finish. Because they are faster to mature than indeterminates, they are often chosen for early crops. Determinate varieties usually bear lightly the first third of the  harvest period, heavily the second, then lightly for the last third, so it is not very productive to plant crops so late that they don’t reach their second (main) month of production before frosts. Determinates need no pruning as the yield of fruit is inherently limited. Most need little staking, but some determinates are quite tall, and produce for quite a long season.

Tomato Mountain Magic in our hoophouse.
Photo Pam Dawling

Fast-maturing Tomato Varieties

Currently Glacier (56d det red) is the only determinate we grow. We simply choose varieties for our early bed based on days to maturity, past experience and inspiring catalog write-ups! They have to be 71 days or fewer from transplant to maturity. We like Stupice (61d ind red), Mountain Magic (66d ind red), Garden Peach (71d ind yellow) and the very fast and delicious cherry Sun Gold (57d ind orange) and Five

Sun Gold cherry tomato in our hoophouse.
Photo Pam Dawling

Star Grape (62d red). We found out the hard way that growing too many cherries is not wise – they take a long time to harvest and when you compare yields it’s clear they don’t add up to much. We grow two plants each of Sun Gold and Five Star Grape, 6 each of Garden Peach and Mountain Magic, 13 Stupice and 16 Glacier. Very biased towards the earliest.


Indeterminate Varieties

Jubilee tomato in our hoophouse.
Photo Pam Dawling

We choose our favorite workhorses along with some unusual heirlooms for our second bed. Most heirlooms are indeterminate. We grow lots of Jubilee (80d ind orange) and Tropic (80d ind red). The just two or three each of the fun and interesting Green Zebra (76d ind green stripes on gold), Striped German (78d ind red/yellow), Amy’s Sugar Gem (75d ind red), Rebelski (75d ind red) and two each of two more cherries, Amy’s Apricot (75d ind apricot) and Black Cherry (70d ind purple-brown)

Green zebra tomato in our hoophouse. Photo Pam Dawling

Indeterminate varieties can continue to grow and produce more fruit as long as the weather is warm enough, and as long as they don’t get struck down by frost or disease. The number of leaf nodes between one cluster and the next remains the same all the way up the vine. Indeterminate tomatoes need substantial support. Pruning is not essential – whether or not to prune depends on your climate, the varieties you are growing and how long you plan to keep the plants for.

Amys Apricot cherry tomato in our hoophouse.
Photo Pam Dawling

Semi-determinate varieties

Semi-determinate tomato varieties are larger than determinate but smaller than indeterminate plants. Some seed suppliers just call them large determinates. These plants usually require staking.

Making Choices

If you are growing in a cold climate you will probably want to grow indeterminates in your hoophouse and keep them all season, as it takes a long time to grow a tomato plant. If you are growing in hot climates, you will probably only grow your earlies in your hoophouse and then grow a succession of outdoor tomato crops. If you grow where there are lots of tomato diseases, you will do better with succession planting than having all your eggs in one tomato basket. If your season is long enough for multiple plantings, you might choose to start with fast determinates to catch the early market.

Jamaica Sustainable Farm Enterprise Program


I’m back from Jamaica, compiling my trip report. I went as a volunteer with a farmer-to-farmer training project for 9 days (plus two travel days). I was a volunteer with the FLORIDA ASSOCIATION FOR VOLUNTEER ACTION IN THE CARIBBEAN AND THE AMERICAS (FAVACA), funded by the United States Agency for International Development (USAID) From the American People established by John F Kennedy in 1961. USAID is the lead U.S. Government agency that works to end extreme global poverty and enable resilient, democratic societies to realize their potential. One of the FAVACA programs is the Jamaica Sustainable Farm Enterprise Program.

For those who don’t know Jamaica at all, let’s start with a map of the island, which is south of Cuba.

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I was hosted by the Source Farm Ecovillage, Johns Town, St Thomas Parish, Jamaica. Here’s a more detailed map with St Thomas parish colored in pink. The Source Farm is east of Morant Bay, very near the coast.

The Source Farm Foundation and Learning Village is a multi-cultural, inter-generational eco-village, located in Johns Town, in the parish of St. Thomas, Jamaica.

“Our ecological mission and vision is to respect natural life, its systems and processes – preserving wildlife and botanical habitat, and creating a life-style that regenerates, rather than diminishes the integrity of the source farm environment.”

Here is a 2014 site map, showing roughly what buildings are there, and where the gardens are located. Actually the gardens have expanded quite a bit since this map was drawn.

I stayed in Earthbag 1, a house built of stacked bags of bauxitic soil with cement, rendered over with cement, giving an adobe effect. The structure stayed fairly cool. The windows had no glass, but insect screens and wood louvered shutters. I’ve never actually had a house to myself before, even a small one like this!

The newer houses in the eco-village are monolithic concrete domes, which hold up very well against hurricanes, earthquakes and termites. Jamaica is rich in marl (lime) and other minerals, and there is a cement works near Kingston. Because many other homes on the island are built from concrete block covered with cement rendering, there are many workers skilled in rendering, who can quickly adapt to dome houses.

I got to taste many kinds of mango, passion fruit, star fruit, star apple, ackee, bammy (cassava flatbread), yam, breadfruit, callalloo (amaranth leaves) and meringa seeds, as well as foods I was already familiar with. I had an especially lovely supper with Nicola and Julia, of snapper with bammy and festival (described by April Jackson on The Yummy Truth as a Jamaican savory beignet made with cornmeal), and Red Stripe beer at Fish Cove Restaurant by the ocean.

Festival, bammy and fish in Jamaica.
Photo https://theyummytruth.wordpress.com/tag/jamaican-fried-fish/

What is on the Farm?

Photo courtesy of
The Source Farm

My teaching work was organized by the people at Source Farm and included the whole group of farmers in JSFEP. The schedule included several farm visits, but unfortunately it rained very hard for four or five days (this was meant to be the dry season!) and many areas were flooded. One farmer told me that the biggest challenges to farming in Jamaica are climate change and theft. Both are serious. The heavy rains I experienced showed how much damage unusual weather can cause. At one farm, where a co-operative onion-growing project was underway, one farmer got trapped by rising waters and had to be helped by two other farmers to swim and wade through the wild waters. After that, the farmers in the group had to take turns to guard the place so that the drip irrigation equipment didn’t get stolen. Another farmer told me about losing an entire crop of sweet potatoes one night – someone dug up the whole lot. The thefts, of course, are related to poverty and desperation in some cases, and a culture where each person has to take what they need as there is little in the way of government support. And a history of colonialism with sugar cane and banana cash crops, followed by a crashing economy.

The roads are in poor shape and in rural areas people rely on calling taxis to get from one place to another. Everyone needs a phone to live this way, and I saw some very battered up phones and chargers carefully repaired and kept running. Arranging a meeting time requires a flexible attitude about timeliness.

The farmers were looking at increasing production, planning planting quantities, scheduling succession plantings, and considering new crops. I met one-on-one with a few farmers, and I did some research into the possibilities of growing asparagus and garlic in the tropics, for a couple of them. I had to get my head round the idea of planting a sequence of three crops each needing four months. No winter cover crop cycle. Cover crops are very different from ours. Some overlap – sorghum-sudangrass, sunn-hemp. But no place for winter cereals! The principle of feeding the soil stays the same, using legumes to add nitrogen, bulky cover crops to smother weeds and add biomass.

I was teaching vegetable crop planning, crop rotations, and scheduling co-operative harvests to help the farmers double their presence at the Ujima Natural Farmers Market  to every Saturday rather than very other Saturday, starting in June. The demand for sustainably grown fresh local produce exists, and farmers are interested in learning to boost production.

On the second Saturday I was there, I gave a workshop on crop planning, to 22 farmers, and we got some lively discussion going, as they offered each other tips, and diagnosed some diseased carrots (looked like nematodes to me).

I treasure the time I spent in Jamaica, even though it wasn’t all sunshine and mangoes. I met many wonderful farmers and enjoyed my stay in the Source ecovillage, which reminded me somewhat of Twin Oaks Community, where I live in Virginia.