Asian Greens for March: Yukina Savoy in the Hoophouse

Koji Yukina Savoy in late December.
Photo Pam Dawling

I wrote about outdoor Yukina Savoy going into the winter, in my October post. Re-read that to get details of days to maturity, cold-tolerance (10F/-12C outdoors) and the differences between the open-pollinated Yukina Savoy and hybrids such as Koji. Five months after that posting we are harvesting the last of the over-wintered Yukina Savoy in the hoophouse. For us, this is a cooking green, not a salad crop. It’s delicious and easy to cook. A little robust for salads, for most people.

Young Yukina Savoy plants in our hooophouse.
Photo Wren Vile

In March we are starting our hoophouse crop transition to early summer crops (tomatoes, peppers, squash, cucumbers) and meanwhile we are enjoying harvests of arugula, brassica salad mix, Bulls Blood beet greens, chard for salad and cooking greens, Russian kales, leaf lettuce, lettuce heads, baby lettuce mix, mizuna and frilly mustards, radishes, scallions, senposai, spinach, tatsoi, turnips and greens and yukina savoy.

We do two hoophouse plantings of Yukina Savoy: the first transplanted from outdoors on October 6, feeds us from December 5 to January 31. The second, transplanted from outdoors on October 24, feeds us from January 8 to early March, sometimes to mid-March. This spring several crops are bolting earlier than hoped-for! We have had some back-and-forth temperatures, which can trigger bolting. Among brassicas, Yukina Savoy is relatively heat-tolerant. This is part of why we do the second planting – it helps us extend the brassica season until we can harvest more outdoor kale.

We transplant Yukina Savoy at 12″ (30 cm) apart in the row, with 4 rows to a 4′ (1.2 m) bed. For a hundred people with lots of other vegetables available, we plant 60 in the first planting and 40 in the second. There are too many other crops competing for space in late October for us to plant more than 40.

Harvesting Yukina Savoy leaves in late November.
Photo Wren Vile.

Initially we harvest this crop by the leaf, until we see the stems start to elongate prior to bolting, when we cut the whole plant. (It is a loose head type of crop, so don’t wait for a firm head to form!)  Actually we pull first, then cut off the head, then bang two roots together to shed the soil, and put the pulled root stumps on the bed to dry out and die. This is easier than cutting first and pulling later. If they do bolt before we get round to pulling them, I have added the pretty yellow flowers to the salad mix. Like all other brassica flowers, these are edible.

Kitazawa Seeds tells us that Yukina Savoy is a Brassica rapa Pekinensis group, for those with a love of brassica botany and those saving seeds. Also those, like us, looking for nematode-resistant vegetables. Brassica juncea are the most resistant brassicas. Kitazawa classifies it as a loose head type of Chinese cabbage.

Yukina Savoy in the early morning mist.
Photo Wren Vile

Twin Oaks Garden blog, rainy day reading, more on hydroponics.

Y-Star Pattypan squash, one of the varieties for the Twin Oaks Garden this year.

Wren, one of the Twin Oaks Garden Managers, has started a blog about the Twin Oaks Garden. This is a great place to check what’s happening in our garden, especially if you also garden in Virginia or some other winter-hardiness zone 7 area.

The new post this week is about What’s New in Spring 2018. There are photos of people at work and also of the new varieties we’re growing this year: Southern Giant Curled Mustard, Purple Peacock broccoli/kale, Canary melon, Flavorburst yellow bell pepper, Y-Star pattypan squash, Royal Burgundy beans (not new to us, but back again), Granny Cantrell’s tomato and Persimmon tomato.

The March issue of Growing for Market is out. Nothing from me this time, but plenty of good stuff from other farmer-writers. Diane Szukovathy writes about starting a 12-member flower producer’s co-op in Seattle. They started with a part-time employee and a simple leased space, working on an indoor farmer’s market model where each farm conducted its own business under a shared roof. They were able to get some USDA funding, and increased their income immediately. Their shared setting was attractive to customers, and a good way to mentor newer growers.

Jesse Frost has written on Understanding Early Blight, with a lot of solid information from Meg McGrath at Cornell (home of the Vegetable MD Online site). Carolina Lees writes about Healthcare beyond hospitals: farm-hospital connections. Ellen Polishuk of Potomac Vegetable Farms offers a Farmer to farmer profile of Richard Wiswall (author of The Organic Farmer’s Business Handbook and designer of many labor-saving devices.) Morgan Houk writes about only collecting useful information when record-keeping, not piles of data you’ll never use. John Hendrickson brings us the latest news on the paper pot transplanter (still not certifiable for USDA Organic farms).

Paper pot transplanter,
Photo Small Farm Works

The Spring 2018 Heirloom Gardener magazine has an article from me about Intercropping (planting two crops side by side in the space normally reserved for just one. In early spring we often sow snap peas down the center of a spinach bed (either an overwinterred spinach bed, or a spring-planted one). The same piece of rowcover warms both (until we whisk away the rowcover to a later crop. The peas grow upwards, not competing with the spinach. When the spinach bolts, the next crop is in place with no further work.

In the summer we have sown peanuts down the center of a bed of lettuce, and transplanted okra into a bed of early cabbage. It’s all about timing and about choosing compatible crops. Okra grows tall, while cabbages stay close to the ground. peanuts grow slowly while lettuce grows quickly.

Overwintered spinach with spring-sown Sugar Ann snap peas.
Photo Kathryn Simmons

Lastly I have more on hydroponics and Organic Certification.

Last week I wrote about the November 2017 vote at the National Organic Standards Board (NOSB) on hydroponics. Since then I’ve read more information, and realized that the view I presented last time is not the whole picture. It is more complex. Audrey Alwell wrote in the Organic Broadcaster for Jan/Feb 2018, reminding us that the 8:7 vote at the NOSB is not a clear stamp of approval for “organic” hydroponics and aquaponics. The NOSB rules require a “decisive vote” (10:5) for a decision. They did not get a decisive vote to prohibit hydroponics from Organic Certification. This means the situation continues for now as it has been. That is, Organic certifiers can certify hydroponic operations of growers using only approved inputs for fertility and pest management, and if they are protecting natural resources and fostering biodiversity.

The Organic label does not cover all the important aspects of ethical and sustainable farming. Not all Organic practices are sustainable. (Think about removing and trashing plastic mulch!) Social justice and fair trade are not addressed. Some hydroponic  growers use renewable energy, some see hydroponics as more sustainable than Organic. In California, during the 6 year drought, hydroponics helped some farmers survive and produce food. Adaptability is important.

One USDA-accredited certifier, CCOF, says all producers should be pushed towards using renewable energy, in order to reduce impact on natural resources. CCOF submitted a 12-page comment.

You can see the USDA Hydroponics Package slideshow.

Continue reading

Real Organic Project, Mother of a Hubbard, Twin Oaks Garden Calendar

The Real Organic Project is taking off where the Keep The Soil in Organic Project is stopping, after several USDA decisions that disregard what organic farmers have to say (allowing hydroponics, setting aside animal welfare, and reducing the role of the National Organic Standards Board.) The hard-working campaigners for genuine organic standards are  disappointed, but are not giving up. Dave Chapman, a leading light of Keep the Soil in Organic, has this report:

“The Past

It has not been a good year for the National Organic Program. Since the November NOSB (National Organic Standards Board) meeting in Jacksonville failed to prohibit HYDRO, the organic community has gone through a period of questioning and searching. We are wrestling with the basic question, “Can we trust the USDA to protect organic integrity?”

Following a series of devastating articles about the NOP (National Organic Program) in the Washington Post last year, all the news from the USDA has been bad. In September, the USDA exonerated the enormous Aurora Dairy CAFO (Confinement Animal Feeding Operation) of any wrongdoing at their Colorado “farm.” This dairy operation was described in detail in one WaPo article, along with compelling test results to prove the cattle weren’t on pasture. The government approval set the stage for Aurora to build several new CAFOs that will dwarf the current 15,000-cow operation.

Then the USDA abandoned the animal welfare reforms (called OLPP) which had finally been approved under Obama. This rejection by the USDA was the result of intense lobbying from such groups as the Coalition For Sustainable Organics (in their Senate testimony), American Farm Bureau, and the National Pork Producers Council. They were championed by the ranking members of the Senate Agriculture Committee, protecting enormous “organic” egg CAFOs in their home states. The USDA thus cleared the way for CAFOs to continue receiving “organic” certification.

Then in January, the USDA announced that “Certification of hydroponic, aquaponic and aeroponic operations is allowed under the USDA organic regulations, and has been since the National Organic Program began.” This was an interesting rewriting of history, but who cares about the facts?

Finally, the USDA recently told the National Organic Standards Board (NOSB) that, going forward, they will be severely limited in the scope of their work. They will not address big questions about organic integrity. They will not set their own agenda. They will limit their focus to defining what substances will be permitted in organic certification.

These outcomes (allowing hydro, setting aside animal welfare, and reducing the role of the NOSB) are exactly what Theo Crisantes of the Coalition For Sustainable Organics called for when he testified before the Senate Ag Committee last year.

It would appear that the USDA is no longer even bothering to woo the organic community with sweet talk. They are bluntly speaking their truth, which is that “Certified Organic” means whatever they want it to mean, and to hell with the organic community. And apparently, to hell with OFPA as well. Organic is all about marketing, isn’t it?

For the many people who have spent years working hard to build the integrity of the NOP, this is a dismal moment. We have lost the helm, and the New Organic will not have much to do with the ideals of such pioneers as Albert Howard and Eve Balfour. It will have to do with money. Money will decide what is called “certified organic” and what isn’t.

And so, if we still care about those ideals, we must move on. The National Organic Program will continue to flourish. Many people will still turn to it to find safer food. Many good people will still work hard to make the NOP as honest and positive as possible. But the NOP will be controlled by politicians and lobbyists who have no belief in the mission of the organic farming movement.

What happens now?

This winter, a growing group of farmers and eaters have formed the Real Organic Project. The Real Organic Project will work to support real organic farming.

This will involve a number of efforts, starting with the creation of a new “Add-On” label to represent the organic farming that we have always cared about. It will use USDA certification as a base, but it will have a small number of critical additional requirements. These will differentiate it from the CAFOs, HYDROs, and import cheaters that are currently USDA certified.

This group grew out of several meetings of Vermont farmers who believed that the USDA label was no longer something that could represent us. Starting a new label is not a small task, but we can no longer find an alternative. That small group of Vermonters has grown quickly into a national group. This amazing group of organic advocates has gathered to build something new.

Standards Board // We now have a 15-member Standards Board, based on the model of the NOSB, but with much greater representation from the organic community. The 15 volunteers have a wealth of experience in both farming and regulation. There are 9 farmer members, as well as representatives from NGOs, stores, consumers, scientists, and certifiers.

The group includes 5 former NOSB members, as well as leading farmers and advocates from across the country. They will meet in March to set the first standards. They will continue to meet once a year after that to review and update. This first year there will be a pilot project with a small number of farms to test the certifying process and work out the details.

Advisory Board // There is also a distinguished Advisory Board that currently has 18 members, including 4 former NOSB members and 3 current NOSB members. It also includes many well known organic pioneers such as Eliot Coleman and Fred Kirschenmann.

Executive Board // And finally, there is an Executive Board of 5 people that includes one current NOSB member.

These boards will work together to reconnect and unite our community. Our intent is transformational. We will create a label that we can trust again.

We can only succeed with your support. Go to to become a member. Make a donation to help make this new label into a reality. We are only supported by our sweat and your generosity. We can reclaim the meaning of the organic label together.


Mother of a Hubbard Cathy Rehmeyer ran a wonderful blog in 2012-2015, with great tips for serious food gardening. Her work Garden Under Cover: Winter Vegetable Production in Low Tunnels is on SlideShare. So far, I don’t think it has appeared as a book. (But it should!)

A flat of newly emerged lettuce seedlings
Photo Kathryn Simmons

And here’s a seasonal reminder about the Twin Oaks Garden Calendarour month-by-month task list for our 3.5 acre, central Virginia winter-hardiness zone 7a vegetable garden that feeds 100 people year round. At the link you will find a photo from each month, which you can click to get to the list for that month. A new season, a new opportunity, using lessons learned last year, along with fresh ideas, inspiration and plain old hard work!

Rhubarb is on its way! So far just clusters of leaves near the ground, but the promise is there! And next week I’ll tell you more about my upcoming book, The Year Round Hoophouse.

Rhubarb in early spring, not yet ready to harvest.
Photo Kathryn Simmons

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.

Asian Greens for December: Pak Choy

Pak Choy in the hoophouse in December.
Photo Ethan Hirsh

December and the first three weeks of January are the season we harvest mature pak choy heads in our hoophouse. Pak choy, also known as bok choi, pac choy, and similar names, is a large 12″-15″ (30–38 cm) tall heading green, usually cut as a full head. If you prefer, you can harvest a leaf or two from each plant each time you want to eat some. It is hardy at least down to 32F (0C) outdoors. Some varieties are hardy down to 25F (-4C).

Botanically, pak choy is a Brassica rapa var. chinensis. If you plan to grow seed of more than one Asian green, carefully choose ones that won’t cross. Be aware of the possibility of brassica crops being wrongly classified.

Pak Choy in the hoophouse in early November.
Photo Pam Dawling

Pak Choy generally has thick rounded white stems, dark glossy leaves and a mild flavor. There are varieties with green stems, some with red-purple leaves such as Red Choi from Kitazawa, and some miniature varieties, such as Mei Qing Choi from Kitazawa, but we grow the full-sized white and green kinds, such as Joi Choi from Johnny’s and Prize Choy from Fedco. For the most choice, go to Kitazawa Seeds, as they stock 23 varieties (although 4 are tatois).

Like all Asian greens, pak choy is nutritious as well as tasty. It’s high in carotenoids, vitamins A and C, calcium, iron, magnesium and fiber. It contains antioxidants which fight against cancer and protect eyes from macular degeneration.

Brassica seedbed protected from insects with ProtekNet and hoops.
Photo Bridget Alsehsire

We sow for this planting in an outdoor nursery seedbed on September 15, and cover the outdoor seedbeds with insect netting. The ideal germination temperature range for Pak Choy is 45-70F, it’s very easy-going. Ideal  temperatures for growth are 60-70F. Hoophouses are perfect. The plants grow fast and we only get a few weeds to deal with.Asian greens have similar care requirements to other brassicas, and very fertile soils grow the best Asian greens.

We transplant as bare root transplants into the hoophouse just 3 weeks after sowing, around Oct 3. We plant 10″ apart, with 4 rows in a 4ft wide bed. We reckon on 52 pak choy plants for 100 people. Because the harvest period is short, it is not wise to grow too many.

Young Pak Choy transplants.
Photo Bridget Aleshire

Pak choy is shallow rooted, so pay extra attention to providing enough water during hot weather , 1” (2.5 cm) of water per week; 2” (5 cm) during very hot weather. This will prevent bitter flavors and excess pungency.

Do closely monitor for pests, which can cause havoc. We have had trouble in the hoophouse from the vegetable weevil larva. Click the link for information and great photos from Debbie Roos at Growing Small Farms. Other possible pests include flea beetles, aphids, harlequin bugs, cabbage caterpillars, grasshoppers and slugs.

Only about 8 weeks after transplanting, pak choy is ready to harvest. Because we want to keep all our hoophouse space in full use, we pull the plant out, then cut off the root. This is easier than cutting the head off at ground level, then trying to pry out the root.

Young Pak Choy plants in early November, with some darker Yukina Savoy on the right.
Photo Wren Vile

That same day we fill the gaps with some younger transplants (sown 10/10 in the hoophouse), that we have in reserve. We call these “filler greens.” We stop filling gaps with Asian greens (and lettuces) on Jan 25, and follow the pak choy with a sowing of kale to be transplanted outdoors in early March.

There’s a good publication from Iowa State Extension on  Commercial Production of Pak Choi. As an organic grower, I don’t use the herbicides and pesticides they mention, but the publication is good on identifying pests and diseases as well as covering the basic growing needs.

See ATTRA’s Cole Crops and Other Brassicas: Organic Production for more information than I can cover here.

In areas with cool or mild springs, pak choy can be a spring green, but that doesn’t work with our short springs – they just bolt rather than size up. Growing outdoors for fall harvest and in the hoophouse for winter use works best here in central Virginia.

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

Asian vegetables for November: daikon and other winter radishes

Frosty daikon – harvest before temperatures drop to 20F
Photo by Bridget Aleshire

I realize this post in my Asian greens series is not exactly a leafy green, but hey, you do what you can. November is the time we harvest winter radishes and wash and sort them. We store the good condition ones in perforated plastic bags in a refrigerator. They store really well this way for several months.

Bucket lid with holes for sorting root vegetables for storage.
Photo Wren Vile

For our other root vegetables we have this bucket lid to help new workers determine what is too small to store. Skinny roots shrivel in storage, so it’s best to eat those up soon after harvest. Winter storage radish doesn’t have its own hole. Deciding what size to store at will depend which variety you are growing. The different varieties can be quite different shapes and sizes.

China Rose winter storage radish.
Photo Southern Exposure Seed Exchange

We like the red-skinned China Rose, which is a round root, which could grow as big as 4″ in diameter. We prefer them at 2-3″ diameter. I’d use the “Turnips” hole or the “Beets” hole in our lid.

Southern Exposure Seed Exchange has this to say about Winter Storage Radishes:

Sow 5-10 weeks before first fall frost. Thin to wider spacing (4-6 in. apart) than regular radishes. Harvest before temperatures drop below 20 degrees F. Trimmed roots can store 2-3 months in the refrigerator or root cellar. These radishes are daylength-sensitive and should not be sown in spring.

Misato Rose radish. Photo Southern Exposure Seed Exchange

Misato Rose is very beautiful. It has an unexciting green and white skin, but inside, a burst of rose and white flesh. Wonderful when sliced or grated for salads. The round roots can grow up to 5″, although I recommend growing them closer and harvesting more of them, in the 3″-4″ range. According to SESE, this is a very forgiving crop – unlike many radishes, this variety will still bulb properly even if over-crowded or thinned late.

Miyashige daikon.
Photo Johnnys Selected seeds

Daikon (pronounced “dye-con”) is the Japanese word for radish. They are usually harvested when 12″ long and 2″-3″ in diameter, though they will grow much larger! Juicy and flavorful, they can be used fresh in salads (grated or thinly sliced), cooked in vegetable dishes (as you would cook turnips), pickled (as in kim chee) or grated with ginger and covered with soy sauce for a dip. They add a wonderful freshness and crunch to winter meals. The cylindrical white roots of Miyashige daikon are pale green near the crown and grow 16-18″ long by 2.5″-3″ across.

Daikons are brittle – they can easily break during harvest. Fork deeply and lift roots carefully. Those that do snap in half can heal over and store just fine.

As well as the true arm-length daikon, there are short stubby “half-long” Korean varieties, for the timid grower.

Black Spanish winter radish.
Photo Southern Exposure Seed Exchange

There is one winter radish I’m not a fan of – the Black Spanish radish. This attractive, round white radish with a matt-black skin has had a tendency to become fibrous, when I’ve grown it. If you’ve had success, do leave a comment, telling about your climate and growing method.

Winter storage radishes are for July and early August sowing, as they are relatively slow growing. We sow August 4 in central Virginia. Don’t try sowing in spring, they will bolt.

Shunkyo Semi-long radish.
Photo Johnnys Selected Seeds

One that can be grown year-round is slow-bolting Shunkyo Semi-Long. This 4″-5″ long, smooth, attractive cylindrical radish has deep pink roots and crisp white flesh. The flavor is a combination of spicy and sweet. The edible leaves are smooth with attractive rhubarb-pink stems.

In November we clear crops from the outdoor garden in this order, and in anticipation of these night temperatures:

25°F:broccoli, fennel, scallions, Chinese Cabbage

20°F: turnips, cauliflower, celeriac, winter radish,

15°F: beets, rowcovered lettuce (the last), kohlrabi, komatsuna, rpwcovered celery,

12°F: fall varieties of leeks, senposai, carrots, cabbage,

10°F: Yukina Savoy, Deadon cabbage, tatsoi, rowcovered scallions.

From December our “Asian greens of the month” will be harvested from the hoophouse.

Cold nights, Cool season hoophouse crops, CASA conference

Ginkgo Golden Puddle Day
November 10 2017.
Photo Pam Dawling

We had a few 24F nights and the ginkgo trees responded by instantly dropping all their leaves. A beautiful sight.

At the Carolina Farm Stewardship Association Sustainable Agriculture Conference I gave a presentation called Sequential Planting of Cool Season Crops in High Tunnels as part of the Friday morning High Tunnel Crop Production Intensive workshop. It’s a new workshop I prepared especially for the CFSA. I usually call the structures hoophouses rather than high tunnels, but either name is fine. It used to be said that farmers called them hoophouses and researchers and academics called them high tunnels. Nowadays there is not such a binary distinction; farmers do research and teach, researchers and academics grow crops. Here is the longer version of the slideshow, including “bonus material” I didn’t include in the 60 minute presentation. Click the diagonal arrow icon to view full screen.

On the Sunday I gave a presentation on Year-Round Hoophouse Production which was a back-to-back presentation of the Hoophouse in Spring and Summer and the Hoophouse in Fall and Winter.  You can view those slideshows by clicking the links to them on the site.

I’ve added a new event to my calendar for January. You can see all the events I plan to speak at, by clicking the Events tab at the top of the screen on my home page. This one is the Chesapeake Alliance for Sustainable Agriculture Future Harvest Conference January 11-13, 2018 at College Park, MD.

On Saturday January 13 11.30am -12.30pm I’m presenting Cold-Hardy Winter Vegetables – Why farm in winter? Information includes tables of cold-hardiness; details of four ranges of cold-hardy crops; overwintering crops for spring harvests; scheduling; weather prediction and protection; hoophouse growing; and vegetable storage.

I might also be participating with other speakers in a new format Lightning Session, where we each get 10 minutes to tell the audience the top 5 things we want them to know about a certain topic. That isn’t decided yet.

I also hope to be signing books at the Southern Exposure Seed Exchange booth at some point.

Meanwhile here on the farm it’s got colder, as I said at the beginning, and even dreary some days. We are getting our winter carrots harvested, getting ready to plant garlic, adding draft-proofing strips to our hoophouse doors, and admiring and harvesting our hoophouse salad crops.

November hoophouse lettuce bed.
Photo Wren Vile

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.

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.