Cold-hardiness zone map, heat zone map and fruit chill hour requirements

 

Our pond iced over.
Photo Ezra Freeman

I was alarmed to hear on NPR that the USDA had issued a new map of winter-hardiness zones. It seemed so recent that we got an update! Relax! (Sort of!) It’s the same 2023 map that I reported on here in November 2023. What is new and worth a visit is the interactive map posted by NPR .

2023 USDA Cold-hardiness zones map

Enter your location and see a map with your zone on the previous 2012 map. Scroll down (it was not immediately obvious to me to do this. . . ) and you can see what zone that area is in now. Scroll further down and you can see the amount the 30-year minimum temperature average has changed since the 2012 map (which used the data from 1976-2005). In my case, Louisa, Virginia has got 3 Fahrenheit degrees warmer in winter on average, than it used to be. Good for keeping some perennials and annuals alive over winter; not so good for fruits requiring a certain number of chill hours, such as apricots.

Our grape rows from the north.
Photo Kathryn Simmons

Fruit and Nut Tree Chill Hours Explained

Apple trees and other fruit and nut trees need cold temperatures to be able to set fruit the following season. Chill hours are the cumulative number of hours during the winter, below a temperature of 45ºF. Nut and fruit trees need a specific number of chill hours each winter to regulate their growth. It is a cumulative total for the whole of the dormant season, whenever they happen. Chill hours are further explained on the Stark Brothers website where there is also this map.Click the link for the ability to zoom in on your location.

Chilling Hours map of the US, for fruit and nut tree growers. MRCC Vegetation Impact Program

Citrus fruits do not need any chill hours. At our farm, we get around 700-800 chill hours each winter. Any tree needing less than 700 will be well served by our winters! Redhaven peaches need 800 – a bit of a gamble. Honeycrisp apples need 800-1000, so they are not for us!

Deke Arndt, director of the National Oceanic and Atmospheric Administration’s National Centers for Environmental Information says that winters are warming at a faster pace than other seasons.

Also, an increase in the quantity and quality of data collected at weather stations across the nation in recent years has helped to increase the overall accuracy of temperature readings. The 2021 data are more accurate than the 2012 data, so the difference (change) over that time is a bit uncertain.

Immature frosty cabbage. Photo Lori Katz

Scroll down the NPR page further, and after a reminder that your zone measurement is an average of the coldest yearly temperature in your area over the past 30 years, you can see a scatter chart of the actual coldest temperature each year from 1991 to 2020. The coldest here was -13ºF in 1996. In that same period, seven winters have had a minimum that was warmer than 10ºF. When you average those coldest nights in each of the 30 years, the average comes out at 4F here. That is, the average coldest night over 30 years was 4ºF.

Scrolling down further we see that puts us in zone 7a, where the average lowest temperature each winter is in the range 0ºF-5ºF. Next comes a reminder that this is only useful for plants that have to survive the winter.

The site focuses on ornamental perennials: You plant them once and they come back after each winter if they’re given the right environment to survive. Think things like trees, shrubs and woody plants. Hydrangeas, Azaleas and Lavender can survive our winters. The Windmill Palm grows in zones 7-11. It might survive here. But, anyway, I’m more interested in vegetables.

A stormy winter day, garlic, rowcovered spinach beds and our hoophouse.
Photo Wren Vile

However, it’s also true that the lowest winter temperature affects annuals that are overwintered to produce spring vegetable crops. Combine the information about your winter-hardiness zone with my Winter-Kill Temperatures of Cold-Hardy Crops list to see what vegetables it is worthwhile keeping in your garden over winter, and which ones will probably survive with rowcover. And which would need a hoophouse or greenhouse to survive.

On its own, your cold-hardiness zone can’t tell you what to grow in your area. For example, parts of Juneau, Alaska; Boston, Mass.; and Santa Fe, N.M are all in USDA’s Zone 7a, as are we in Louisa, VA.

Juneau has relatively temperate winters that are extremely wet, averaging over 80″ snow a year. Santa Fe is extremely dry, with much hotter summers than Juneau. Boston has temperate winters and temperate summers. It gets rain, but not nearly enough for Juneau’s rainforest plants to thrive. It gets heat in the summer, but is colder and wetter in the winter, preventing desert plants like cactuses and other succulents from thriving.

Because all these three cities rarely get below 0ºF each winter, they are all classified as zone 7a.

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

Here are some things to keep in mind about winter-hardiness zones:

  • Your winter temperature can still dip below your hardiness zone. Remember, your zone is a measure of the average coldest night in 30 years. Some years are above average, others are colder!! Even much colder! In 2014, the temperature in St Louis (zone 7a) dipped three half zones below St. Louis’ hardiness zone, to -10º F. So be alert to the threat of extreme cold snaps. And find a way to keep your plants warmer until the snap passes.
  • The hardiness map says nothing about the frequency of extreme cold weather. A plant or an animal can survive an occasional short dip to a temperature much colder than usual. But an extended period of very cold weather is more deathly.
  • Sweet potatoes in storage. An ideal crop for winter meals, as they store at room temperature for a long time, maybe seven or eight months.
    Photo Pam Dawling
  • The hardiness map can’t tell you if your plants will survive the summer.  I have had people ask me what zone sweet potatoes can grow in. My reply is that winter-hardiness zones will not affect sweet potatoes, because they are not out there in the soil in the winter! They are in your basement or a root cellar or a storage room, above 55ºF.
  • AHS Heat Zone Map 1997
  • For thinking about summer temperatures, consult the 1997 American Horticultural Society heat zone map that measured the average number of times per year that the temperature of an area exceeds 86ºF. The heat zone map is on the NPR site, if you scroll far enough. With 60-90 days a year with a high temperature above 86ºF, Louisa, VA is in heat zone 7 of the 12 created. I hope an update of this map comes soon.
  • If your winter-hardiness zone has changed, you could plant some new things, or leave plants such as figs, or spinach, that you previously wrapped each winter, unwrapped.
  • Warm microclimates such as containers on paved surfaces or near brick buildings absorb a lot of radiant heat during the day and hold it into the night.
  • Remember the cold-hardiness zone calculations are using the past 30 years’ data. If you notice temperatures are continuing to climb, year after year, you could experiment with less-hardy plants from the half-zone warmer than yours.
  • Your local Extension Service may be able to help with more local information.

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/

http://thesourcefarm.com/the-farm/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.

 

 

 

 

Book Review: Weeds by Richard Mabey

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Book Review: Weeds: In Defense of Nature’s Most Unloved Plants, by Richard Mabey. 2012 Ecco Paperbacks.

Richard Mabey has just had a new book published (The Cabaret of Plants) but I am behind the times, and another of his books, Weeds, has been my delightful summer reading. Weeds was published in the US in 2012, after a 2010 publication in the UK with a different subtitle. I remember enjoying his book Food for Free in the early 70s, when I was a student about to embark on my adult life. He is probably Britain’s foremost nature writer.

This is a lively book, full of strange tales, literary references, fascinating rich details, reflections on civilization, and musings on what might have been, given a different wrinkle of history. It is about weeds in relation to people: cultural history and botany, global travel and trade, pharmaceutical research and the avid gardening of exotics. There is a good 9-page glossary of common and Latin weed names, 7 pages of notes and references and a very well-crafted, thorough 15 page index.

Each of the twelve chapters has the title of a weed (real or fictional), and a beautiful line drawing. Confusingly, this is sometimes a different weed, or the one of the title is lurking in the background of the drawing. Richard Mabey says “Weeds are our most successful cultivated crop.” He disagrees with Michael Pollan who said that “as weeds may be, they cannot survive without us any more than a garden plant can.” Mabey is confidant they’d survive without us!

imagesRichard Mabey’s story starts in the mid-60s in outer London, near Heathrow Airport, where he had an editing job in a derelict area of gravel pits, Victorian rubbish dumps, scrap yards and a dirty canal. In summer, he walked there in his lunch breaks. The area became a green jungle including “immigrant plants from three continents,” as a result of seeds brought there deliberately or accidentally. Weeds green over the dereliction we create. One role of this book is as a defense of weeds, an appeal to regard them more dispassionately, perhaps helped by the tales of how they got here, or why, or when.

In 1855 Richard Deakin wrote the Flora of the Colosseum of Rome, and listed 429 species of wild plants on the 2000 year old ruin, including 41 members of the pea family. Some of these plants were rare in Western Europe and may have arrived in the fur of the North African animals brought there for torturous combat with gladiators. Fifteen years after this book, Garibaldi’s government ordered a big clean up and almost all the plants were removed.

In 1877 a well was sunk 1,146 feet in London, down to 500 million year old rocks. In those Old Stone Age layers were fossils of some weeds we still have today.

At the beginning of the twentieth century, Edward Salisbury found a new weed growing on a heap of flints: ragweed imported with the flint ballast from a US ship. He also found blue pimpernels in his newly-claimed-from-turf garden in Radlett, Hertfordshire, plants which had not been seen in England for a hundred years. In 1945 he listed 126 bomb site plants.

Charles Darwin dug a 3 foot by 2 foot patch and observed the germination of 357 weed seedlings (boo!). 295 were destroyed by slugs and insects (yay!). And while we’re counting species, it has been reported that the stomach of Graubelle Man, one of the Iron Age Bog People, contained seeds 63 weed species, along with barley and linseed, possibly a ritual last meal before being sacrificed.589141

During World War II, unusual weeds erupted on London’s bomb sites. “A weed storm, a reminder . . . of how thinly the venue of civilization lay over the wilderness,” says Mabey. Poppies germinated on Europe’s battle fields wherever the soil was disturbed (by digging trenches, or by dropping bombs.) In 1964-71 the US sprayed 12 million tons of Agent Orange over Vietnam. It killed entire rainforests and laid low very many Vietnamese people. 80 years later, the forests have still not regrown. The vacuum has been filled by Cogon Grass, which used to grow along forest edges. Relatively recently, Cogon grass reached the southern US in the packaging of imported Asian house-plants. Is this some botanic poetic justice? Cogon is number 7 among the world’s worst weeds. It even overwhelms bamboo.

In the 1980s, Graham Atkins found a barnful of topsoil that had been intended to restore a quarry when it was worked out and returned to agriculture. A test patch grew weeds that had not been seen for decades. Dock seeds germinate after 60 years, lambsquarters (fat hen) after 1700 years, weld (dyer’s rocket) after 2000 years burial. The seeds can go dormant deep in the soil profile.

The UK spent £70 million to clear Japanese knotweed from the 2012 London Olympics site. All plants in the UK are female, and clones of earlier arriving pieces.  This weed can spread 6 feet down and 20 feet sideways in a single year. Ground Elder roots can go down 30 feet, and it can grow 3 feet sideways in a single season. In what I take to be a “know thy enemy” move, this weed has been charmingly named Grelda by Richard Mabey’s partner Polly, with whom he lives in Norfolk, England.

Richard Mabey has a lot of life experience, which shows in his broad-ranging literary, historical and cultural references (including Virgil’s account in the Georgics of Jove’s creation of weeds, weeds in Shakespeare, in John Clare’s poems, and Elizabeth Kent’s essays). Enough stories of weeds for now – on to weed management, a topic of great concern to gardeners everywhere. In Europe in the Medieval Period, weeds were not hoed, but individually hand pulled with the aid of two sticks, one forked, one hooked.

This is not a book prescribing weeds as medicine, although the topic receives some attention as history. Sympathetic Magic – plantain leaves to heal crushing and tearing injuries, because plantain leaves bounce back after being crushed. The 17th century Doctrine of Signatures, a very human-centered approach to weeds (they exist for our benefit) suggested that dandelions have yellow petals not because yellow attracts insects, but to tell us it is useful for urinary disorders. Most herbal medicine these days  is based on observed effectiveness, although it may be surprising to learn that some of the Doctrine of Signatures beliefs still hold sway.

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Galinsoga (but may not be parviflora) Photo by Wren Vile

The chapters meander weedily from one topic to another. There are many fascinating tales of how plants came to be imported to the UK. Kew Gardens received a gift of Galinsoga parviflora (named after a Spanish botanist) in 1793. It escaped in the 1860s. “Oxford ragwort” (possibly brought from Mount Etna in the mid-18th century) escaped after about a hundred years in the Oxford University Botanical Garden, and after another 50 years, was found in much of the south of England. It then spread across bomb sites in the 1940s, presumably bomb craters offered similar conditions to volcano craters.

Britain was landfall for huge numbers of foreign plants, and the Kew Gardens collection of drawings and dried specimens has been analyzed by mineralogists for mineral content to determine where best to mine certain minerals. Other industrial “spin offs” from weeds include the inspiration for Velcro found in burdock seed heads. For reasons lost to us, burdock was a popular plant in landscape painting in the 17th and 18th centuries.

In 1638 and 1663 in the US, John Josselyn published lists “Of Such Plants as Have Sprung Up since the English Planted and Kept Cattle in New England“. There were 22 species.

And in the US today, lawns apparently occupy an area the size of Iowa, and lawn grasses are the most highly sprayed crop, (including both herbicides and fertilizers). Such is the price of Fear and Loathing of Weeds.

Weeds sometimes get moved accidentally, and grow in their new homes after calamities. Sometimes they are imported as exotic garden plants. Sometimes a rare woodland plant like Rosebay Willowherb (Fireweed) takes off when new opportunities arrive, such as stony track-beds of railway lines, fire sites and bomb sites. The plant adapts over time.

Courtesy http://i-spy-in-queenspark.blogspot.com/2012/07/weeds.html
Courtesy I Spy in Queen’s Park

Such flourishing adaptations feed into real and imagined worries about herbicide-resistant SuperWeeds, sci-fi weeds like triffids, cross-over genetically engineered weeds and escaped GM crops like canola. Every now and then an especially troublesome weed rises to the top of the worry list. In 1970 in the UK, children were erupting in facial blisters and welts. It was a fad that summer to use the hollow stems of Giant Hogweed as telescopes, whistles and blowpipes. Giant Hogweed, like its relative Wild Parsnip, contains furocoumarins, which are activated in sunlight and then cause skin damage. Giant Hogweed had been around since the early 19th century, but no-one had thought to play in the sunshine and touch the stems to their eyes or lips. As a result, the UK Wildlife and Countryside Act of 1981 made it an offence to tolerate the growth of this impressive 12 foot tall plant with cart-wheel sized flowerheads.

A Weed Extermination Industry followed in the wake of government legal attacks on weeds. The UK Environmental Protection Act of 1990 classified Japanese Knotweed as “controlled waste” and made public money available to help with extermination. Businesses flourished, spending the funds on lavish websites, conferences and manuals. There were strict protocols (rituals, exorcism rites), a step-by-step process, a correct time of year for action. The UK Finance Bill of 2009 allowed tax relief of 15% on costs of removing knotweed from “contaminated land”. Extermination companies took advantage by raising their price for clearance to more than £50/square meter. Then a tiny sap-sucking insect was found which shows promise as a biological control.

Was the Japanese knotweed panic justified? No, says Mabey. The method of tallying noxious weeds used 10km by 10km squares. The incidence was 83% of squares infested in the worst areas. But looking instead at 2km x 2km squares reduced the incidence of infestation from 83% to 29% of squares.

Some panic about invasive aliens is misplaced. Or rather, the affection felt for natives is misplaced. In the UK, many plants considered valuable natives are not so: horse chestnut, snowdrop, many modern cultivars of daffodil, Alexanders. Beware not only of unrealistic ways of measuring, but also of false sympathies and snobbery. In 2005, Ted Green wrote a provocative paper arguing that climate change ought to make us “rethink the relevance of taking a dogmatic position on native and non-native trees.” Evolutionary survival strategies of non-natives may counter the unpredictable demise of other species.

The remaining Plotland bungalow
The remaining Plotland bungalow

I was particularly interested in one of the examples of plants reclaiming urbanized spaces. The New York High Line, Detroit and Chernobyl are other examples, but because I live in an intentional community I was intrigued by Plotland, a community near Basildon, Essex, which was established at the end of the 19th century, during the agricultural depression in the UK. It consisted of self-built chalets and shacks, and at the height of it’s success, there were 8,500 homes, each with a vegetable plot.

Remains of a home in Plotland
Remains of a home in Plotland

Sadly, the water and sewage systems were found inadequate, and in 1949 the Plotlanders were rehoused in Basildon New Town. Most of the buildings were cleared by the mid-1980s, under a plan to reinstate the area as farmland. But the steep site and the poor soil meant there were no buyers. In 1989 the Development Corporation declared the ghost town to be  Langdon nature reserve.

A natural succession followed. At first lawn grasses, weeds and garden perennials grew. Plums, apples and garden shrubs grew bigger. Oak, ash, hawthorn and hornbeam followed. These native hardwoods shaded out the more delicate domesticated cultivars.

And now the UK has a Biodiversity Plan – there is government support for increasing the population of 20 arable weeds, some of which were regarded as pestilential nuisances 300 years ago. We have come to understand the need to accept the existence of weeds. Herbicides have made some of them resistant, some of them rare. We need to balance practical control with cultural acceptance. We get the weeds we deserve.

As I was gathering materials for this post I discovered another Central Virginia Organic Gardener who had reviewed WeedsJudy Thomas

Ate more Eat-All Greens; Changed vegetable crop rotation

Eat-All Greens radishes on October 19. Photo Bridget Aleshire
Eat-All Greens radishes on October 19.
Photo Bridget Aleshire

Our Eat-All Greens are still alive, if not exactly thriving. The peas have been harvested to death; the kohlrabi, beets and chards are never going to amount to anything; some of the more tender Asian mustard greens are showing some frost damage.

On 12/10 we made one last crew foray to harvest – not greens, but roots! I’d noticed in the wet mild weather of late November the radishes and turnips had fattened up. We can always use a few more turnips, I thought. Plus, I was inspired by the quick-pickle radishes we’d had recently. See sustainexistence sustainable sustenance for our existence, the local foodie blog written by one of my fellow Twin Oakers. 

As we were harvesting the two and a half buckets of radishes, someone came by who said he was planning to pickle radishes, so I told him we’d keep him busy! (Actually, ten days later, there are many left to deal within the walk-in cooler.) The daikons predictably did well, as they are a fall crop. Other good varieties included Crimson Giant, which I picked up at a seed swap, and White Icicle. Sparkler (a small radish was unsurprisingly tough and woody at this overgrown stage.

We also pulled a 5-gallon bucket of delectable small turnips, including some rather pretty Mezza Lunga Bianca Colletto Viola from Seeds from Italy.

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Meanwhile we have been working on our garden planning for next year. Back in 1996 we devised a 10-plot crop rotation, which has generally served us very well for 19 years. The first few years we tweaked it a bit, but we haven’t needed major changes. You can see our pinwheel rotation plan in my book Sustainable Market Farming and in my slideshow Crop Rotations for Vegetables and Cover Crops  on SlideShare.net.

Here you can see the original card version, complete with modifications. The central card disk is fastened with one of those brass-legged paperclips and can be turned one notch each year.

Original Twin Oaks Garden Crop Rotation Pinwheel
Original Twin Oaks Garden Crop Rotation Pinwheel

The bit we want to change is the fast-turnaround where the spring potatoes are followed by the fall broccoli and cabbage. This has worked well in terms of getting high usage from our land, and freeing up one plot in ten to be Green Fallow (all-year cover crops). We did that by undersowing the fall brassicas with clover about a month after transplanting, and then letting the clovers grow for a year and a half before disking in. The difficulties with such a fast turnaround in July are

  1. If we have a wet spring, and we plant the potatoes late, we have to terminate them early (by mowing the tops) and the yield isn’t as good as it might have been. Climate change suggests we might be in for more wet springs, and with El Nino upon us, this is a good time to switch.
  2. If the weather doesn’t co-operate in July, the soil might be too wet to harvest the potatoes when we want to, and too wet to disk in preparation for the transplanting. We need to build more climate resilience into our rotation!
  3. July is stressful enough – it’s hot and humid, people are taking their turn at having a vacation.
  4. If we are late transplanting the broccoli and cabbage, the plants are oversize and don’t do well, so we get reduced yields of broccoli and cabbage that year.
  5. We prefer transplanting in the evenings in the summer (cooler for us and for the plants), and if we get late into August, the daylight is getting too short to get much done.

And so, we are seizing the opportunity to make the switch. The opportunity comes because for the last several years we have not needed to grow winter squash in the vegetable garden because it is grown elsewhere on the farm by the Twin Oaks Seeds.

Fall broccoli undersown with clover. Photo Nina Gentle
Fall broccoli undersown with clover.
Photo Nina Gentle

Our crop rotation contains several sequences of crops that we want to keep. For example, Fall brassicas/Green Fallow/early spring crop (Could be corn or potatoes, but not the spring broccoli and cabbage). Another sequence that works well for us is the Early corn/Garlic next to spring brassicas/fall carrots in one half, rye vetch and peas for no-till cover crop in the other half/paste tomatoes on the no-till the next year.

What we’ve planned for next year (a transition to our new plan) is to use the former winter squash plot for the fall brassicas/clover bit. This involves snipping that plot out of the pie and moving it after the corn #6/sweet potato and the spring potato/cantaloupe (which had morphed into 100% potatoes over the years), so that the newly housed fall brassicas can be followed by the clover year.

But that leaves potatoes only two years after other potatoes, and the late corn only two years after the middle corn, so we don’t want to do that more than once! So for 2017 onwards, we plan to insert the late corn & sweet potato/spring potato sequence after the clover, and move the early corn after the spring potatoes (when we have time to plant a winter-killed cover crop and make cultivation for the early corn easy). And switch the watermelon piece of the pie with the 3rd, 4th and 5th sweet corn successions to even out the years between corn patches.

June planted potatoes with hay mulch. Photo Twin Oaks Community
June planted potatoes with hay mulch.
Photo Twin Oaks Community

This will give potatoes, tomatoes, potatoes 3 or 4 years before the plot is nightshades again. With the corn  we get 3 years, 5 years and 2 years. Not ideal. But we don’t get much in the way of corn diseases (compared to tomato diseases) so it seems the best place to compromise.

If you get bored with holiday jigsaw puzzles and TV offerings, you could draw up your own version of our rotation, chop it up and rearrange it, and send us you suggestions. Remember to plan the winter cover crops too! Have fun!

Who likes my blog?

It’s the time of year when I start to review what’s working well and what needs tweaking for the next growing season. I’m applying this to my blog as well. Here’s what I’ve discovered:

Favorite topics are growing sweet potato slips and harvesting sweet potatoes, winter hardy crops, reviews of books by Janisse Ray and Bill Best, trimming and sorting garlic, and garlic planting, weeding zombie carrots (I suspect some non-gardeners check that one!), climate change and winding up driptape for reuse.

Top searches (other than things directly related to my book) include:

sweet potatoes, quick-cut greens harvester, crop rotation chart, Growing for Market, cicadas, slideshare.net, Proteknet, senposai, and market farming.

Senposai, the Thousand Wonder Green, Credit Kathryn Simmons
Senposai, the Thousand Wonder Green,
Credit Kathryn Simmons

Someone in almost every country has visited my site. Hopefully people in Greenland, the Svalbard islands of Norway, Paraguay, Papua New Guinea, Azerbijan, and twelve countries in central and western Africa will find it useful at some point!

Goodbye winter, hello summer!

Rhubarb season is almost here. Credit Kathryn Simmons
Rhubarb season is almost here.
Credit Kathryn Simmons

Spring in Virginia is so variable in temperature! But this year is more so than usual. We’ve just had three days with high temperatures of 90F (31C) or more. Not so long ago we had night-time lows of 20F (-6.5C). Late February and all of March was full of snow and rain.

The only thing we managed to plant in the garden for the whole of March was a small amount of shallot bulbs. We’ve been doing an impressive amount of scrambling in the first ten days of April, to make up for lost time. Some crops we had to cut back on, because it got too late to plant. We only have a quarter of the onions we planned, half of the peas, a fifth of the spinach, and no fava beans this year. I realize it would be useful to have “last worthwhile planting dates” for all our spring crops, to help decision-making.

To add insult to injury, a Beast ate half of our early broccoli transplants in the cold-frame one night. Because there were big surface tunnels, I think it was Eastern Moles. They are insectivorous, not vegetarian, but they do use leaves to line their nests, which they make at this time of year. I bought a trap – no luck. I covered the remaining broccoli and lettuce flats as best I could with rat wire “lids” and clear plastic domed food covers – things I had handy from previous depredations. What seems to have worked is to line the coldframes with landscape fabric and set the flats on that, tightly up against the edges, leaving no wiggle room. Wisely, we do a later, third, sowing of broccoli to cover emergencies, so we spotted those out into bigger flats. We’re going to need them this year.

Chitting seed potatoes ready for planting. Credit Kati Folger
Chitting seed potatoes ready for planting.
Credit Kati Falger
Newly emerging potato plant in the spring Credit Kathryn Simmons
Newly emerging potato plant in the spring
Credit Kathryn Simmons

We have at last got our potatoes in the ground, three weeks later than ideal. On the positive side, they had been chitting (green-sprouting) in crates under lights in the basement since the beginning of March, so I could console myself that they were growing anyway. And probably they will come up quicker in the (suddenly!) warmer soil. We cut them for planting once the area was disked for planting and we were pretty sure we could get them in the ground in a few days.

We’ve busily transplanted spinach, kale, lettuce and scallions, and sowed carrots, more scallions and the third bed of beets. We used the Earthway seeder for the beets, and found the radish plate worked better than the beet plate for Cylindra seed, which were smaller than the Detroit Dark Red. We also tried the popcorn plate with some success, when the beet plate jammed.

We flamed one of our first two beds of beets, to kill the weeds that didn’t die properly with our hasty delayed rototilling. We would have flamed both, but the Cylindra popped up overnight earlier than I expected (going by soil temperature), so we’ll have to hoe those really soon, maybe this afternoon.

Spring bed of cabbages planted into rolled hay mulch. Credit Kathryn Simmons
Spring bed of cabbages planted into rolled hay mulch.
Credit Kathryn Simmons

Next we’ll be prepping our cabbage and broccoli beds. We make temporary raised beds, roll out round hay bales over them, then transplant into the mulch. We do this by first measuring and making “nests”, using our hands to open up the mulch down to the soil. The brassicas appreciate the mulch to moderate the soil temperature and keep some moisture in the soil.

Our big weeding projects have been the raspberries and the garlic.(Goodbye, henbit!)

 

Mar 2013 Growing for Market
Mar 2013 Growing for Market

Today we might sow our parsnips. I just wrote an article about them in the March issue of  Growing for Market. This issue also contains articles about increasing hoophouse tomato production, adding solar panels, equipment for tracking the weather, food safety and new interesting cut flowers.

Florence bulb fennel. Credit Southern Exposure Seed Exchange
Florence bulb fennel.
Credit Southern Exposure Seed Exchange

The April issue is also out. For that, I wrote about fennel – bulbs, leaves, seeds and pollen. Other articles include one about Johnny’s Salanova lettuce, others about training cucumbers and tomatoes up strings in the hoophouse, a tractor implement for rolling out round hay bales (which is only fun to do by hand the first ten times, max), more on food safety, and an interview/field trip to Texas Specialty Cut Flowers. 

GFM-April 2013-cover-300px

Phenology – What happens when

Flowering Purple (or Red) Dead Nettle, with honeybee.Credit Kathryn Simmons
Flowering Purple (or Red) Dead Nettle, with honeybee.
Credit Kathryn Simmons

For ten years I have been keeping phenology records, as a guide to when to plant certain crops, and as a way of tracking how fast the season is progressing.

Phenology involves tracking when certain wild and cultivated flowers bloom, seedlings emerge, or various insects are first seen. These natural events can substitute for Growing Degree Day calculations. Certain natural phenomena are related to the accumulated warmth of the season (rather than, say, the day-length), and by paying attention to nature’s calendar you will be in sync with actual conditions, which can vary from year to year, and are changing over a longer time-scale..

Many people know to sow sweet corn when oak leaves are the size of a squirrel’s ear. By this point, regardless of date, the season has warmed enough to get oak leaves to that size, which happens to be warm enough for sweet corn seed to germinate and grow well. Some people transplant eggplant, melons and peppers when irises bloom; sow fall brassicas when catalpas and mockoranges bloom; and know to look for squash vine borers laying eggs for the two weeks after chicory flowers. Some transplant tomatoes when the lily of the valley is in full bloom, or the daylilies start to bloom.

Lilac is often used to indicate when conditions are suitable for various plantings:

  •   When lilac leaves first form, plant potatoes
  •  When lilac is in first leaf (expanded), plant carrots, beets, brassicas, spinach, lettuce
  • When lilac is in early bloom, watch out for crabgrass germinating
  • When lilac is in full bloom, plant beans, squash, corn. Grasshopper eggs hatch.
  • When lilac flowers fade, plant cucumbers.

Also, recording the dates of the same biological events each year can show longer term climate changes. In Europe, 500 years of recorded dates of grape harvests provide information about summer temperatures during that time. Project Budburst is a citizen science field campaign to log leafing and flowering of native species of trees and flowers across the US each year. Each participant observes one or more species of plant for the whole season.

 Here’s our Twin Oaks Phenology Record so far:

(c) Pam Dawling, 2013

Event 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 Notes
Crocus blooming 26-Jan 25-Jan 6-Feb 10-Feb 28-Feb 17-Feb 30-Jan
Chickweed blooming 8-Feb 1-Jan 5-Mar 10-Feb 13-Mar 19-Feb 13-Feb 15-Feb
Robins arrive 27-Feb 31-Jan 20-Jan 26-Feb 2-Mar 14-Feb
Henbit blooming 14-Mar 7-Mar 12-Jan 6-Jan 7-Feb 20-Feb 22-Mar 2-Mar 15-Feb 15-Feb
Daffodils blooming 17-Mar 9-Mar 7-Mar 1-Mar 22-Feb 3-Mar 5-Mar 15-Mar 3-Mar 17-Feb Plant potatoes
Dead-nettle blooming 18-Mar 6-Mar 7-Mar 8-Mar 14-Mar 9-Feb 24-Feb 13-Mar 21-Jan 22-Feb 10-Feb
Spring Peepers first heard 4-Mar 11-Mar 10-Mar 3-Mar 3-Mar 6-Mar 11-Mar 28-Feb 23-Feb 5-Mar Plant peas
Overwinter Grasshoppers seen 26-Feb 4-Apr 25-Feb
Maples Blooming 10-Mar 6-Mar 15-Mar 12-Mar 28-Feb
Dandelion blooming 16-Mar 16-Mar 24-Jan 1-Jan 3-Mar 17-Mar 9-Mar 8-Mar 19-Mar Sow beets, carrots
Forsythia blooming 13-Mar 12-Mar 28-Mar 10-Mar 23-Mar 13-Mar 17-Mar 21-Mar 15-Mar 12-Mar 15-Mar Plant peas. Crabgrass germinates.
Peach blooming 15-Mar 25-Mar 26-Mar 25-Mar 13-Mar
Cabbage White Butterfly 25-Mar 20-Mar 7-Mar 8-Mar 11-Mar 6-Apr 24-Mar 12-Mar 14-Mar Dutch white clover blooms
Harlequin bugs 10-Apr 13-Mar 26-Mar 12-May 16-Apr 29-Apr 14-Mar
Johnny Jump-up blooming 16-Mar 30-Mar 14-Mar 20-Mar 3-Apr 17-Mar
Flowering Cherry blooming 27-Mar 4-Apr 3-Apr 1-Apr 6-Apr 25-Mar 17-Mar 18-Mar 20-Mar
Asparagus spears 6-Apr 4-Apr 4-Apr 5-Apr 6-Apr 6-Apr 21-Mar 19-Mar
Redbud blooming 5-Apr 13-Apr 9-Apr 3-Apr 2-Apr 7-Apr 9-Apr 7-Apr 4-Apr 19-Mar Expect flea beetles
Smartweed germinating 15-Apr 10-Apr 15-Apr 6-Apr 11-Apr 1-Apr 23-Mar 20-Mar <149 GDD base 48F
Lambsquarters germinating 20-Mar 20-Mar <150 GDD base 48F
Violets blooming 29-Mar 26-Mar 28-Mar 6-Apr 22-Mar 20-Mar
Morning Glory germinating 27-Apr 10-Apr 3-Apr 26-Apr 24-Apr 25-Apr 22-Mar >349 GDD base 48F
Tiger Swallowtail 19-Apr 29-Mar 15-Apr 16-Apr 18-Apr 10-Apr 28-Mar
Apples blooming 18-Apr 20-Apr 14-Apr 7-Apr 12-Apr 28-Mar
Dogwood (Amer.) full bloom 5-Apr 21-Apr 13-Apr 28-Mar Plant peppers; soil 65 F
Strawberries bloom 13-Apr 11-Apr 14-Apr 12-Apr 4-Apr 2-Apr 15-Apr 6-Apr 8-Apr 30-Mar
Lilac full bloom 16-Apr 20-Apr 21-Apr 22-Apr 19-Apr 21-Apr 14-Apr 18-Apr 1-Apr Plant beans, squash
Crimson Clover blooming 29-Apr 2-May 16-Apr 22-Apr 23-Apr 27-Apr 18-Apr 25-Apr 4-Apr
Whippoorwill first heard 1-May 22-Apr 15-Apr 24-Apr 17-Apr 25-Apr 8-Apr 14-Apr 5-Apr
Galinsoga germinating 1-May 22-Apr 16-Apr 20-Apr 6-Apr
White Oak “squirrel’s ear” 20-Apr 26-Apr 23-Apr 26-Apr 25-Apr 14-Apr 23-Apr 12-Apr Plant sweet corn
Tulip Poplar blooming 2-May 10-May 3-May 26-Apr 3-May 6-May 26-Apr 28-Apr 17-Apr Plant sw corn 200 GDD base 50F
Ragweed germinating 20-Apr 16-Apr 25-Apr 26-Apr 21-Apr Plant sw corn 200 GDD base 50F
Last Frost 24-Apr 4-May 3-May 1-May 8-May 17-Apr 19-May 10-May 14-Apr 25-Apr Average 4/30 (10 yrs)
Fireflies 7-May 2-May 1-May
Colorado Potato Beetle adult 22-May 3-May 7-May 29-Apr 27-Apr 3-May 25-Apr 2-May
Strawberries ripe 10-May 17-May 12-May 10-May 7-May 15-May 3-May 10-May 7-May
Purslane germinating 26-May 8-May 22-May 5-May 20-May 15-May 8-May
Baby Grasshoppers 12-Jul 30-Jun 26-Jun 17-Jun 16-May
Cicada first heard/seen 14-May 5-Jul 3-Jul 29-Jun 17-May
Hardneck garlic mature 14-Jun 19-Jun 13-Jun 5-Jun 4-Jun 30-May 9-Jun 11-Jun 6-Jun 31-May
Foxgloves bloom 6-Jun 11-Jun 8-Jun Bean beetle eggs hatch
Bean Beetle eggs 4-Jun 16-Jun 10-Jun 6-Jun 20-Jun Hatch when foxgloves bloom
Japanese Beetle first seen 16-Jun 21-Apr 15-Jun 20-Jun 29-Jun 21-Jun 850 GDD (base 50F)
“June” Bugs first seen 5-Jul 11-Jul 2-Jul 12-Aug 10-Jul 30-Jun 29-Jun 30-Jun 23-Jun
Corn Earworm first seen 28-Jul 8-Jul 12-Jul 10-Jul 14-Jul 150-490 (base 54F)
Fall Dead-nettle germinating 1-Sep 20-Aug 30-Aug 20-Aug 16-Aug 20-Aug 15-Aug 29-Aug 18-Aug Plant spinach
Fall Henbit germinating 28-Aug 20-Aug 29-Aug 18-Aug
Fall Chickweed germinating 7-Sep 7-Sep 5-Sep 6-Sep Plant spinach
First Fall Frost 3-Oct 6-Nov 27-Oct 13-Oct 29-Oct 20-Oct 19-Oct 23-Oct 30-Oct 22-Oct Average 10/22 (9 yrs)
Harmonia Ladybugs migrate east 18-Oct 12-Nov 21-Oct 27-Oct
Garlic planted (hardneck) 25-Oct 20-Oct 9-Nov 3-Nov 11-Nov 1-Nov 5-Nov 11-Nov 15-Nov 6-Nov Soil temp 50 F
Event 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 Notes

Starting sweet potato slips

Growing sweet potato slips from roots planted in flats of compost.Credit Kathryn Simmons
Growing sweet potato slips from roots planted in flats of compost.
Credit Kathryn Simmons

The weather outside is still full of rain, but I’m optimistically starting growing our own sweet potato slips. Surely it will dry out by May?

Sweet potatoes are related to morning glory, in the genus Ipomoea. They are not yams, even though they are often called yams! True yams are a tropical species of tuber (genus Dioscorea). Sweet potatoes are roots, not tubers, and will not even cross with yams. So forget yams. Unlike white potatoes, which have the annual plant sequence of vegetative
growth, flowering and dying back, sweet potato plants would continue growing forever if the weather was warm enough.

The mystique of sweet potato slips

Sweet potatoes are not grown from seed or from replanted roots, but from “slips,” which are pieces of stem with a few leaves, grown from a mother root. We used to buy bare-root sweet potato slips to plant, believing growing our own would be very tricky. The collapse of our supplier and our desire to have organic plants (plus a need to reduce our expenses one year), pushed us into growing our own. We had some problems initially, so I can warn you about how not to do it. Now we have a system we really like, and we’ve found several advantages of homegrown slips over purchased ones.

With purchased slips, we had to specify a shipping date months ahead, then hope the weather sprites would be kind. We had to jump to when the plants arrived, and get them all in the ground pronto, to keep them alive as best we could (because their roots needed moisture). We accepted as normal a certain amount of drooping. We can have late frosts, spring droughts or El Niño wet springs, and climate change is only adding to the uncertainty. With homegrown slips we can delay planting if that seems wise; we can plant them in stages rather than all on one day. The transplants don’t wilt. We can grow them big and plant them with three to five nodes underground, giving more chance of survival in heat or frost. We can keep some spares on hand to replace casualties. The sturdy plants get off to a strong start, which could be an even bigger advantage further north where the season of warm-enough weather is on the short side for a 90–120-day plant. And we are self-reliant — we never have to spend money on them.

Timing

Figure out your ideal planting date and work back to find your starting date. Planting is usually done about two weeks after the last frost. The soil temperature should reach at least 65°F (18°C) at 4″ (10 cm) deep on four consecutive days. For us, that’s around May 12. It takes eight weeks to grow the slips, and the roots produce more slips if conditioned for two weeks (or even four), before you start to grow slips. So start ten to twelve weeks before your planting date. We now start March 1. Here’s where I made my first big mistake — following directions written for much further south, I tried to start growing slips in mid-January. Dismal fight against nature!

Testing (Optional)

If you want to get the best yields from your mother roots, first test the roots in a bucket of water — the ones that float are said to yield better and produce better-flavored roots. Next, test for viral streaking — also known as color breaks or chimeras, where paler spots or radial streaks appear in the flesh — and discard roots with pale spots or streaks wider than a pencil lead. Cut a thin slice from the distal end of each root — the stringy root end, opposite the end that was attached to the plant stem. All the sprouts will grow from the stem end, so don’t cut there! If you can’t tell the difference between the ends, you can ignore this step and plan not to propagate your own slips for more than a couple of years (so the virus load doesn’t get too high). Or if you are a home gardener dealing with a small crop, you could keep the slips from each root separately and cut up the mother root before planting and then discard the slips from streaked roots.

Conditioning (Also Optional)

Put the chosen roots in flats, boxes or trays, without soil, in a warm, moist, light place for two to four weeks. Ideal conditions are 75°F–85°F (24°C–29°C) at 95% humidity. This can double or triple the number of sprouts the root will produce in a timely manner. We use our germinating chamber, which is an old glass door refrigerator heated by a light bulb. See the photo above. Conditioning after testing allows the cut surfaces to heal before they are covered by compost. The environment for sprouting the roots is similar, so you can probably use the same location.

Sprouting

Set up a place with light, humidity and ventilation at 75°F–85°F (24°C—29°C) and with about 12″ (30 cm) of headroom. Plant the selected roots almost touching each other, horizontally in free-draining light potting compost in flats or crates. Water the boxes and put them to sprout. Once again, we use our ex-fridge germinator. Using boxes is much more manageable than having the roots loose in a big coldframe. Indoor spaces are much easier to heat than the great outdoors! Boxes can be insulated and put on a bench at a decent working height, with lights or heat lamps over them. Keep the compost damp, and if your planting medium is without nutrients, give liquid feed occasionally once sprouting starts. For small quantities of slips, it is possible to sprout the potatoes half-submerged in water, either in trays of water or by suspending a sweet potato impaled on toothpicks, resting on the top of a glass of water. For larger quantities I recommend our method.

Cut sweet potato slips put in water to grow roots.Credit Kathryn Simmons
Cut sweet potato slips put in water to grow roots.
Credit Kathryn Simmons

Cutting and spotting the slips
After 5–7 days, the roots will begin to produce slips. Ideally, wait until the slips are 6″–12″ (15–30 cm) tall with 4–6 leaves beginning, then cut them from the root and stand them in water. If necessary, cut them a bit shorter. Some people pull or twist the slips from the roots, but this could transfer diseases by bringing a small piece of the root with the sprout. I cut the slips daily, bunch them in a rubber band and stand them in a small bucket of water. The slips will grow more roots while they are in water for several days, which seems to be an advantage. Once a week I spot (plant) the oldest, most vigorous slips (with good roots) into 4″ (10-cm) deep wood flats filled with compost. The spotted flats require good light in a frost-free greenhouse and sufficient water. If you are two weeks away from your planting date and are short of slips, you can take cuttings from the first flats of slips that were spotted, to make more. The slips planted in flats become very sturdy, allowing flexibility about planting dates and a longer slip-cutting season. About ten days before planting, start to harden off the flats of slips by reducing the temperature and increasing the airflow. It’s also possible to skip the spotting stage and transplant the slips outside directly from the water, but I don’t think this is as good as spotting them into flats of good compost for a few weeks.

Once a week we plant the rooted slips in flats.Credit: Kathryn Simmons.
Once a week we plant the rooted slips in flats.
Credit: Kathryn Simmons.

From Sustainable Market Farming, (c) Pam Dawling, New Society Publishers 2013