We’ve already prepared our first bed in the hoophouse and sowed our first few crops (spinach, radishes, scallions, tatsoi, Bulls Blood beets and cress). We spread the bed prep out over 5 days and the sowings over 2 days. I’ve written lots about our fall hoophouse planting, so I’ll give you links, mention a few updates and stick to photos otherwise.
Hoophouse Winter Schedule Tweaks and Improvements (pack more crops in, get higher yields, reduce or spread the workload). One change we made was to sow some early catch crops in areas that weren’t needed for all-winter crops until later. We mostly used tatsoi and Tokyo bekana, both fast–growing leafy greens. We intended to grow some early beets too, but the seed didn’t germinate. A new crop last winter was cress, Creasy Greens Upland Cress and Belle Isle Upland Cress from Southern Exposure. They take 50 days to maturity (in spring). We had two good intentions we did not manage to follow through on. One was to let some of the cress flower, to feed beneficial insects. And I think we got too impatient. The other was to notice which one of the two kinds we prefer and just grow that one. We didn’t manage to keep good enough records on that, so this winter we are obliged to repeat the experiment, with more good intentions!
Fall hoophouse bed prep and shadecloth removal (packing away the giant piece of shadecloth until May, spreading compost, broadforking and raking the beds, direct sowing the first bed, sowing seeds in an outdoor nursery bed to transplant into the hoophouse a few weeks later). This post includes a step-by-step guide to hoophouse fall bed prep. Our soil is improving each year, becoming easier to broadfork and rake. That counters the aging process of our human bodies! One change we made last year was to measure and pin down the drip tapes 12” (30 cm) apart, and use the drip tape as a guide to making furrows (drills). This is easier than using the row marker rake, as we used to do.
Sowing hoophouse winter crops(more details on bed prep tools and techniques, including the row marker rake if you want to use that, and links to posts about winter lettuce varieties we used in 2017/2018.)
Planning and Growing Winter Hoophouse Vegetables(hoophouse crop map, many links to other posts including a video and three slideshows, crop rotations, choosing winter hoophouse crops, posts about specific crops (with all the details), back up plans in case something goes wrong, and harvesting.)
Preparing your hoophouse for fall and winter(includes one of my slideshows, and a more detailed discussion of lettuce types and sowing dates, information about salt build-up and our wash-down strategy in a 3-slide mini slide show, when we close and open the doors and windows, and a Be-Prepared Winter Kit list)
Winter hoophouse growing (includes a round-up of earlier posts, and a discussion about the value of crop rotation in the hoophouse, and a list of 20 benefits of having a hoophouse.)
Spinach variety trial conclusions This year we are growing Acadia. Johnny’s do not recommend this variety for late fall or winter sowing, but it did very well in our hoophouse, sown in September, October, November and January.
Note: the day after I posted this I found I was mistaken in believing barley to die at a warmer temperature than oats, so I’ve edited it.
Focus Cover Crops for September: Winter Wheat and Crimson Clover
In August I wrote about cover crops such as millets, southern peas, buckwheat which are frost-killed. If it’s still too early to sow your winter cover crops, sow summer cover crops. Before I get to the wheat and crimson clover, I’ll mention some other useful seasonal cover crops.
Winter-killed, not frost-killed, cover crops
There are also cover crops that are not frost-killed, but die later in the winter, at colder temperatures, such as oats and barley. Only sow oats or barley if you are sure you can get them turned under or killed by cold winter weather before they seed. They will not mow-kill, so if the weather doesn’t kill them, you will have to turn them under. Be careful buying feed-grade seeds (rather than Organic seed-grade), as they can contain weed seeds including GMO canola.
If the area is clear of vegetable crops by 40-60 days before frost, sow oats to winter-kill. If possible add a legume (soy and spring peas are easy, and will be killed by the frost, so they won’t complicate food crops next year). For us with a first frost date of October 14-20, the cut-off date for oats is September 7, or September 15 if we really push it. Sowing too late means you don’t get enough growth in the fall, and the soil is not adequately protected from erosion or from weed growth.
We sow oats after growing early sweet corn, spring broccoli, spring-planted potatoes, cabbage, kale, or early season spinach, lettuce, beets, carrots. Spring oats die after three nights at 20°F (-7°C), or a single plummet to 6°F (-17°C), leaving the plot quick to prepare for early crops next year. Winter oats are hardier, but my goal with growing oats is for them to die in winter. After oats or other winter-killed cover crop, we like to plant our early spring food crops, peas, cabbage, broccoli, carrots, March-planted potatoes, spinach and the first sweet corn.
Fall-sown barley (Hordeum vulgare), grows even faster than oats, but not as quickly as winter rye, and it won’t die as early in the winter as oats. Barley dies at 17°F (-8°C). It usually will die in Zone 7 and colder regions. The dead barley residue protects the soil through the winter, and dries into what Barbara Pleasant calls “a plant-through mulch” in spring in cold zones.
See Planning Winter Cover Crops, a post that includes my Short Simple Guide to Winter Cover Crops and my slideshow Cover Crops for Vegetable Growers. Oats, barley, wheat and rye sown too early can head up and seed before you get to winter, making them less useful, and more of a weed problem.
Winter-hardy grass cover crops to sow in September
It is too late for us to usefully sow cover crops that are not frost-hardy, as they won’t make enough growth before getting killed.
Winter rye and winter wheat are two grass cover crops that can be sown in the mid-Atlantic in September. Wheat is easier to incorporate than rye and has less of an allelopathic effect on small seeds, the inhibition of germination that lasts three weeks after rye is turned under. It’s true wheat doesn’t produce as much biomass as rye, so there’s the tradeoff. We sow wheat if the area is ready for cover crops 20-40 days before frost. This allows us to make faster use of those plots in the spring, compared to plots sown to rye.
For us wheat is a good, trouble-free winter cover crop. Winter wheat prevents erosion, suppresses weeds, scavenges excess nutrients, adds organic matter, encourages helpful soil microorganisms, and the fine root system improves the tilth. It is less likely than barley or rye to become a weed; easier to kill than barley or rye; cheaper than rye; easier to manage in spring than rye (less bulk, slower to go to seed); tolerates poorly drained, heavier soils better than barley or oats. If you have leftover seed, wheat can be sown in spring – it will not head up, but “wimps out” when the weather gets hot.
The challenges of wheat are that it does not have good tolerance of flooding, and is a little more susceptible than rye or oats to insects and disease.
Secondary cover crops in September: Include legumes where possible
With careful planning, you can grow next year’s fertilizer for your later spring-planted vegetables! Legumes grow nitrogen-fixing bacteria on their roots, which can feed the next food crop. You may need to buy a suitable inoculant if you are introducing a new legume species. You may decide to inoculate anyway, for insurance, even if that type of legume is already somewhere in your garden. Before sowing the legume seed, dampen it, sprinkle the inoculant over the seed at a “pepper on your dinner” rate, and stir it in. Then sow the seed. Be sure not to make the seed wetter than slightly damp, or you’ll need to spread it out to dry a bit before you sow.
Two other key parts of being successful are to sow the legume early enough to establish before winter halts growth, and to plan not to need that plot next year until flowering time for that legume. At flowering time, legumes have the maximum amount of the nitrogen nodules they will have. Don’t let the legume flowers set seed, or they may become a weed problem. Take notes on when various legumes flower. If you have a legume that doesn’t reach flowering, it’s not the end of the world, you just get less nitrogen for your money, and won’t be able to supply all the N needs of the following food crop.
September (40-60 days before frost) is a good time to sow clovers here, provided you can supply enough overhead irrigation. They will make some growth in our climate before winter, and then a lot more once spring arrives.
Crimson clover is a good September choice, if you won’t need to prepare the area before it flowers (in central Virginia 4/16-5/2, most usually around 4/20).
For a cover crop to survive the winter, sow winter wheat with Austrian winter peas, crimson clover, hairy vetch, red clover, white clover or fava beans. Hairy vetch takes a few weeks longer than crimson clover to reach flowering. Which you choose will depend what you want to grow there next spring and when you need to plant it.
Clover for green fallow in early September
See August’s post for info on planting a Green fallow plot (Full year cover crops)
Time is running out on this for us, but you may still have enough warm weather where you are. A green fallow crop (all-year cover crop) will replenish the soil and reduce annual weeds for the following year. In late August, or early September, four weeks after transplanting your fall brassicas, especially cabbage and broccoli, but also kale and collards, broadcast a mix of clovers: 1 oz (30 g) Crimson clover, 1 oz (30 g) Ladino white clover and 2 oz (60 g) Medium red clover per 100 sq ft (9 m2). Crimson clover is a winter annual and will be the biggest and the first to flower, in April. Medium red clover is a biennial and will be the next to flower. White clover is perennial and will take over the plot as the others subside. Be sure to get the medium red clover, not the Mammoth kind that dies when mowed. Likewise, for maximum benefit, get the tall Ladino white clover, not the low-growing “wild” type. In March, mow down the old brassica stumps and let the clovers flourish. You will be mowing this patch about once a month from March to October next year to prevent the crimson clover and the annual weeds from seeding.
Cover crops to sow soon after your first frost date
I’ll say more about this next month, and because I want this website to be useful to a geographically wide range of growers, I’m including a preview here. If the area is ready for cover crops up to 10 days past the frost date, sow winter wheat or winter rye with hairy vetch or Austrian winter peas. Winter rye is hardier than any other cover crop and can take later planting dates. But it is a bit harder than wheat to incorporate in the spring. Sow winter rye from 14 days before to 28 days after first fall frost. See Working with the time you have leftin the Summer Cover Crops post. Austrian winter peas can be sown later than other legumes, it’s too late for clovers.
My book Sustainable Market Farming has a chapter on cover crops and many pages of charts about particular options.
Those who start early in “spring” (late winter) might get earlier crops, but when is it worth it?
Some crops are just not going to thrive if you start too soon: cucumbers, peppers, and even tomatoes, for example. Make sure you can provide conditions that meet the minimum temperature requirements for these tender crops. See my book Sustainable Market Farming, for all the details. We used to start these tender crops earlier than we do now. March conditions have become more unreliable, often colder.
If you already have a place to grow protected crops, or you are experienced with rowcover and have plenty on hand, then the signs are good. Crops can be started earlier in a greenhouse or hoophouse (or even on a kitchen windowsill) than you can sow them outdoors. When the plants reach a good size, harden them off and then plant them out in a mild spell, with rowcover for the first couple of weeks. Pay close attention to weather forecasts.
“Hardening off” is a process of acclimating your plants to colder, brighter, breezier conditions, so that they won’t suffer when they are transplanted. If you have only a small number of plants, or of flats, you could actually bring them back indoors every night and set them out every morning for 10-14 days. Growers with lots of crops to harden off will make use of a coldframe. Depending on the actual temperature (or the expected night-time low) we might leave our plants uncovered, use rowcover, top the rowcover with transparent lids (“lights”) , and if it’s going to be really cold, quilted covers, weighted down with wood beams if it is the least bit windy.
After two weeks of hardening off, look for a few days of mild, calm weather to plant them out in the garden. Water the plants well the day before transplanting, and again one hour before transplanting. This allows the cells of the plants to fill up with water, enough to tide them over the period of “transplant shock”.
Even the most skillful of us end up doing some damage to the roots of transplants, and that means the plants have to regrow some lateral roots and root hairs before they can pull in water at the rate they were doing before your ministrations. As you transplant, avoid touching the roots of the plants. Our fingers damage the root hairs.
A way to minimize the root damage is to use soil blocks or Winstrip plug flats. These methods are more expensive in time or money than open flats or bare root transplants, but they allow the roots to get “air-pruned” as they grow. When the roots reach the air at the edges of the blocks, or at the vertical slits on the sides of the Winstrip cells, they stop growing, rather than circle around the cell, causing the plant to get root bound. Secondly, these tools work by helping the roots and compost form a coherent block, one that holds together as you pop it into the hole you create in the soil.
Speedling flats are styrofoam flats with tapered cells, and it is possible to slide the plugs out (or gently pull them out) with little damage. Regular cell packs (4-packs, 6-packs etc) can be encouraged to release their transplants by squeezing them at the base of a cell, while holding the pack sideways. Then spread your fingers over the compost around the pant, invert the pack and hopefully the plant and its compost stays as an item, with your fingers either side of the stem.
Hold the plant with one hand by a seed leaf, or if you have to, by the stem. The seed leaves are disposable, stems and roots are not! Hold the plant at the right height, usually with all the stem below the leaves in the ground and all the leaves above ground. Once the plant is in the ground at the right height, hold it there and use the other hand (maybe with a trowel) to push in soil to fill the hole. Firm the soil down quite well, pulling in more soil as needed to leave a level surface. You don’t want the plant to be in a divot, where water can accumulate.
About the degree of firmness: you are aiming to make good contact between the soil and the plant roots, so the roots are not in air pockets, but rather can suck in water from the between soil particles. Don’t firm so hard that you expel the air from the soil and make what feels like concrete the next day. With cabbages, I was taught to firm enough so that if you then grasp a leaf and pull, the leaf tears off, rather than pulling up the whole plant.
Plant for 20-30 minutes, then pause and water in each of the new transplants by hand. Some people will bring a watering can along the row and water each one, one at a time. I prefer to do little batches. At the end of you transplanting session, water the whole row or bed again. try to avoid having piles or dishpans of plants with roots exposed to the air. Definitely don’t take a tea break if you have exposed plants.
Cover with rowcover if needed, or shadecloth if the weather is very bright and sunny. This will just be for a few weeks, helping the plants recover from the transplant shock, and biding time while spring warms up.
If it doesn’t rain, water again the next day (day 2), then on days 4 and 6, then twice a week, then once a week forever after that, until harvest is completed.
Blueberries are easy to grow if conditions are right. They are a popular choice with organic growers, because they don’t need any pesticides to produce a good crop. They do, however, need annual pruning to be sure of a high quality crop. Pruning also keeps the bushes at a height easy to harvest from. Pruning is done during the dormant season, usually between December-early March in the Piedmont.
Some people are reluctant to prune because it does remove some of the flower buds and reduces berry production for that year, but if pruning is not carried out, berries become smaller each year and the health of the bushes declines. Pruning is an investment in the long-term success of your plants!
The Growing Small Farms website links to many how-to videos and fact sheets, with diagrams and photos. There are excellent resources on pruning and blueberry production in general. Everything you need to know about pruning blueberry bushes!
Another good resource is this article in the Agricultural Research Service newsletter
“We focus on improving the shelf life of fruit so that it reaches consumers with consistently better texture and flavor,” said Claire Luby, plant geneticist with HCPGIR. Perhaps a large challenge for Luby and her colleagues is developing a cultivar that is resistant to a disease known to be a scourge of the berry: blueberry shock virus.
“We’re studying diverse blueberry plants to understand the genetic basis for blueberry shock virus, which can significantly impact yields for farmers,” she said. “Our hope is to use the insights from this project to develop new cultivars that are resistant, or at least more tolerant to, the disease.” Blueberry shock virus has caused annual crop losses of 34-90% in the Pacific Northwest.
Researchers combine traditional plant breeding with genomics to create their disease-resistant cultivars. The traditional technique (used in one form or another by people trying to improve agricultural crops for millennia) is to take pollen from one plant and use it to pollinate a different plant with complementary characteristics. They study the progeny of these crosses, looking for new characteristics that meet the goals of the breeding programs. Traditional blueberry breeding can take more than 20 years from the time an initial cross is made to when a consumer might eat from a resulting cultivar.
“We try to improve the accuracy and speed of the plant breeding process,” Luby explained. “We are now able to obtain a lot more genetic information about the plants and we can use that information to potentially predict whether an offspring of a given cross might have the characteristics we are looking for before we plant it out in the field. This is important because it can increase the speed of the plant breeding process.”
“Our goals are to develop blueberries that require fewer chemical inputs to fight disease, which can be better for both the environment and for growers’ bottom lines,” Luby said.
The Agricultural Research Service is the U.S. Department of Agriculture’s chief scientific in-house research agency. Daily, ARS focuses on solutions to agricultural problems affecting America. Each dollar invested in U.S. agricultural research results in $20 of economic impact.
Crop Planning for Sustainable Vegetable Production
At the in-person Pasa Sustainable Agriculture Conference, I gave two presentations. I also sent a recorded workshop for their virtual conference in January. That one was Feeding the Soil. I’ve just scoured through all 8 pages on my website that check the category “Slideshows”. I found Feeding the Soil twice.
My Alliums Year Roundpresentation is new this year and I posted the handoutafter my presentation at VABF. Pasa had shorter workshops, so I pruned the slideshow, but left the handout with the “bonus material”.
My other presentation at Pasa was Crop Planning for Sustainable Vegetable Production. That is one of the very first topics I tackled when I started out as a speaker, so the three versions on this website span the past ten years. 2014, 2016, 2019. Here is the 90 minute 2023 version and ts handout:
The conference was very well-attended, and not everyone at my workshop on Friday, or the Alliums Year-Round 90 minute workshop on Sunday morning got a handout. I promised to post them here, and now I’m making good. I’m also posting the handout for the third workshop I gave, Asian Greens in the Winter Hoophouse. This rounds out the set, and gives a chance to those who went to a different workshop at that time to get a look in.
In January 2020 I was part of a group tour of Cuban farming organized by the Organic Growers School. In 9 days we visited 9 farms, had several speakers address aspects of life (and particularly farming and environmental issues) in Cuba, had a couple of walking tours, ate many delicious farm-to-table type dinners and still had time for a salsa lesson.
When I got home I planned to follow up with a public slideshow, but instead we got the Covid pandemic. I made a series of blogposts, which you can revisit:
“This 9-day tour of Cuba’s sustainable farms, community gardens, and historical centers provides a rare opportunity to learn about the Cuban food system and learn about alternatives to corporatized agriculture. Participants will have the chance to:
Learn from farmers and food activists about Cuba’s transition to agroecological farming practices and its national policies that prioritize sustainable farming and hunger remediation.
Connect with farmers, consumers, activists, NGOs, policymakers, and experts working to transform the global food system.
Acquire the knowledge and strategies to create just, sustainable, local, and healthy food systems in your own communities.”
Check out the linked presentation for a summary of the January 2022 tour and for a sneak peek of the types of activities involved in the tour. OGS successfully operated a tour group in January 2022. No-one got Covid. OGS brought the first educational trip from the United States to Cuba since the beginning of COVID
On the website you can get your most likely questions answered: legal, financial and health requirements, sample itinerary, reasons to visit Cuba, reasons to go with OGS, reasons to value agroecology, and a one-hour Info session video. The trip includes bus transportation within Cuba, a minimum of 2 meals each day, 9 nights in casas particulares accommodation, a very good ag-knowledgeable tour guide and tour manager, and entry fees to various sight-seeing exhibitions.
CAFF - Extend Your Growing Season into Colder Weather with High Tunnels I’m spending October home on the farm, preparing and planting the hoophouse with winter crops. Meanwhile I’m applying to speak at quite a few sustainable agriculture conferences and preparing slideshows, handouts and talks. I’m going back to in-person conferences. We have very limited Wi-Fi in this part of rural Virginia and video-conferencing is just not possible. I managed to make some recorded narrated slideshows during the pandemic and I picked up more writing work. But there is an undeniable something I get from in-person conferences!
In the past year I’ve been at two in-person events: The very safely and carefully orchestrated PASA conference back in February, and the September CAFF presentation, half of which was outside touring the farm and half in a large airy lecture room. Now I’m lining up quite a few conferences. Go to my Events page on this website to get all the details, including links to register. Hope to see you at one of these:
I will be presenting a 75-minute workshop on Spring and Summer Hoophouse Use, especially how to manage extreme heat and diseases in hot and humid climates.
January 6-8 (Fri-Sun), 2023, Virginia Association for Biological Farming is hosting the Virginia Biological Farming Conference, Hotel Roanoke and Conference Center. Conference INFO Home Page
I hope to be presenting a half-day pre-conference session on Friday January 6, on Year-Round Hoophouse Vegetables. Also maybe a regular length session during the main conference.
January 14, 2023 (Saturday), NOFA-MASS Annual Winter Conference. Northeast Organic Farming Association, Massachusetts Chapter.https://www.nofamass.org/conferences/Worcester State University on Saturday January 14 and online Sunday January 15. I hope to give a presentation on Saturday.
February 8-11, 2023 (Weds to Sat 2.30pm), PASA2023 Sustainable Agriculture Conference. Lancaster Marriott Hotel and Conference Center, 25 S Queen St, Lancaster, PA. https://pasafarming.org/conference/
I will be presenting two 60 min or 75 min workshops:
Alliums Year-Round (Brand New!)
Crop Planning for Sustainable Vegetable Production.
We are getting ready for fall and starting to plant our winter crops in the hoophouse.
I have written about transition to winter crops here: Planning and Growing Winter Hoophouse Vegetables (August 16, 2022). This post includes a bed plan, and links to lots of related posts, such as selecting and planning winter crops, bed prep, direct sowing and transplanting, and then caring for the crops, optimizing use of the space, harvesting, and what to do if something goes wrong,
Fall Lettuce Transition
From September 11-17 we sow to transplant in our greenhouse, and on September 15 and 24 to transplant in our hoophouse. This is our fall transition and I’ll write about that when the time comes.
On September 15 and 24, we sow leaf lettuces and romaines in an outdoor nursery bed. We transplant these into our hoophouse at 10” (25 cm) spacing. This is a bit closer than the 12” (30 cm) spacing we use outdoors. We will harvest outer leaves from the hoophouse lettuce all winter, so the plants won’t get as big as they do outdoors.
On October 23 we start sowing lettuce mix in the hoophouse. Baby lettuce mix can be ready in as little as 21 days from mid-spring to mid-fall, longer in colder weather. Our first sowing will be harvestable form 4 December to 15 May if we’re lucky, although if it gets too hot, this planting will get bitter and we’ll need to pull it up.
Baby lettuce mix is a direct-sown cut-and-come-again crop, the plants regrow and can be harvested more than once in cool seasons. We sow 10 rows in a 4’ (1.2m) bed, 4.5” (11cm) apart. Weed and thin to 1″ (2.5 cm). When 3″–4″ (7.5–10 cm) tall, cut 1” (2.5 cm) above the soil. Gather a small handful in one hand and cut with using large scissors. Immediately after harvesting, weed the just-cut area so the next cut won’t include weeds. Rake after harvest with a fine leaf rake to remove outer leaves and cut scraps. If you want to make more than one cut, you will need to remove anything that isn’t top quality salad while you can see it. Larger scale operations have harvesting machines.
We make four or five sowings of baby lettuce mix, sowing our last one on 15 February, for harvest starting mid-March, and ending in May when it gets too hot. By then we should be happily harvesting juicy lettuce heads outdoors and will have lost interest in the lettuce mix.
The soil temperature range for germination of lettuce seeds is 35-85°F (2-29°C), with 40-80°F (4-27°C) being the optimum range and 75°F (24°C) the ideal. At 41°F (5°C) lettuce takes 15 days to germinate; at 50°F (10°C) it takes 7 days; at 59°F (15°C) 4 days; at 68°F (20°C) only 2.5 days; at 77°F (25°C) 2.2 days. Then time to germination increases: 2.6 days at 86°F (30°C); after that it’s too hot.
Removing Shadecloth from our Hoophouse
We are now removing our shadecloth. Normally we would have removed the shade cloth in mid-September, or at least by the Equinox, but this year we are delayed a week. After 15 years with our initial piece of shadecloth we ordered a new piece. Well, we ordered two new pieces, because we mistakenly ordered a piece only half long enough. We bought a matching piece for the other half, and this winter we are going to sew the two pieces together with nylon twine, because the ends of each piece roll back, leaving a central gap about 6 feet long by September. Measure twice, order once!
Before next spring we need to replace quite a lot of the hooks the shadecloth ropes attach to. Next time we replace the big plastic we also need to replace the baseboards, as they are rotting and not holding the hooks well.
A reader passed on this tip: “When I ordered shadecloth for my hoophouse, I overshot each end by ten or twelve feet. We stake that out on either end, using six-foot T-posts, to give us a shaded area where air moving into the hoophouse’s open ends can be cooled before entering the structure. Every year in July and August, I’m grateful we did.”
Washing Down the Salts in the Hoophouse
Next week we will leach the salts that have risen to the surface of the soil and dried out there. My book The Year-Round Hoophouse has a whole chapter on recognizing, monitoring and reducing salts that have built-up in the hoophouse, and reducing the likelihood of problems in the future. There is also a chart of salt tolerance of various vegetables, so you can choose what to grow while you remediate your soil. Here I’ll just give a very short intro, in three slides. Click in the lower left of the first slide to move to the next one.
We are starting to close the doors at night when the temperature looks likely to drop below 50°F (10°C) outside. We had to trim down the grass to be able to push the doors to. We had to re-drill the holes the door-bolts (“cane bolts”) go down into. The doors have been wide open all summer.
In fall/winter/spring, if night time outdoor low temperatures will be below 40°F (4.5°C) here, we close the windows as well as the doors.
See my post Dealing with winter weather in your hoophouse (Jan 2022). Be ready to deal with snow and strong winds, extra cold temperatures, and holes in the plastic letting cold air in. If you have a double layer hoophouse, the air inflated between the layers adds strength to the structure, as well as thermal insulation. Holes are bad news.
SnoBrum and telescoping painter’s pole
Hat with visor
Long-handled broom with bristles covered with a towel or some bubblewrap
If you have a hoophouse, you may now be planning or planting crops for fall, winter and spring. If you don’t have a hoophouse, this is a good time of year to consider getting one. See Twenty Benefits of Having a Hoophouse at the end of that post. There are grants available from NRCS, including reparation levels of funding from traditionally underserved groups of people. There are now companies that will construct your hoophouse for you, if you don’t want to do it yourself, or can’t. If you do want to build your own, there are detailed instructions in my book The Year-Round Hoophouse. You can buy the book here on my Books page direct from me, or from my publisher New Society, or you can buy it wherever books are sold.
I have many posts about winter hoophouse vegetables, so rather than try to write something completely new on the topic, I am going to give you a guide to find your way around the information already here.
Sweet potatoes are grown from “slips,” (pieces of stem with a few leaves), grown from a mother root, not from seeds or replanted roots. We used to buy bare-root slips for transplanting, because we didn’t know how to grow our own, and had heard it wasn’t easy. We have been growing our own for many years now, and prefer the flexibility and reliability it gives us. We did make several mistakes initially, so I can warn you about what not to do. We have a system that we really like, and I have learned a few other methods that I will also tell you about, including one I helped out with the past two years, growing them in a hoophouse.
Disadvantages of buying sweet potato slips
You need to specify a shipping date months ahead, then hope for good weather and no shipping delays.
You might have late frosts, spring droughts, or El Niño wet springs, and climate change is only adding to the uncertainty, but slips that arrive in the mail need immediate attention.
You have to get them all in the ground promptly, and do your best to keep them alive (because they arrive wilting).
Some amount of drooping (transplant shock) is normal.
Advantages of growing your own sweet potato slips
You can delay planting if the weather is all wrong (frost, drenching rain, heatwave)
You can grow them big and plant 3-5 nodes underground, giving more chance of survival if there is a late frost, or an early drought.
You can plant them in stages rather than all on one day.
You can grow extra and keep them on hand to replace casualties.
The sturdy plants get off to a strong start – the transplants don’t wilt – a big advantage where the warm season is on the short side for a 90- to 120-day plant.
You have more self-reliance and less money going out.
How not to grow sweet potato slips
I made several mistakes learning to grow slips. You don’t have to repeat my mistakes! My first error – following directions written for much further south (in pre-internet days), was to try growing slips in mid-January in central Virginia. Dismal fight against nature! Likewise, I was puzzled by talk of using cold frames. Ours were freezing cold at that time of year.
Next, I set up a soil warming cable in a cinder-block-enclosed bed on the concrete floor of our greenhouse. This is how I discovered most soil warming cables have thermostats that switch off the heat at 70°F (21°C). I just couldn’t get the soil warm enough.
Three Successful Methods of Growing Sweet Potato Slips
Twin Oaks slips-in-flats method
Boutard single node cutting method
Hoophouse or caterpillar tunnel bedding method (Twin Oaks)
Twin Oaks Slips-in-Flats Method
I’ve written about this before, so I’ll just give you a link to open another page.
Starting Sweet Potato Slips discusses pros and cons of growing your own slips, and describes our “slips in flats” method, which I learned from Hiu Newcomb of Potomac Vegetable Farms. Here is our Worksheet we use to stay on track with that task.
Anthony Boutard and Caroline Boutard Hunt wrote an article about single node sweet potato propagation (which they learned from John Hart of Cornell) in Growing for Market in March 2015. They farm in Oregon and New York respectively.
Both the slips-in-flats method and this one start at the same time, planting roots in damp compost in a warm greenhouse. I corresponded with Anthony Boutard about our respective methods. He pointed out that the slips-in-flats method needs a lot of warm space to grow the slips, at a time when warm space is at a premium. Our method does take us from early March to mid-May.
The single node cutting method uses only 10-20% of the number of mother roots compared to the slips-in-flats method. It uses tiny plants in plug flats, saving on greenhouse space, and only needs 18 days between cutting the slips and planting in the field. The smaller plants can experience less transplanting shock than larger plants. On the other hand, I do not think they have the resilience that multi-node plants have, for example if a late frost strikes.
When these plants grow in the field, their root production is from the single node. This can lead to fewer, but very large tubers, an advantage or a disadvantage, depending on your goals. Better in climates with a short warm season than in hot places, although digging after a shorter growing period would be possible in warm climates.
This method can be used to grow more plants from purchased cut slips, which is very helpful if you are growing a rare heirloom with limited propagation material available. Plant the bought slips in the greenhouse and grow them on until you can make cuttings.
Like the slips-in-flats method, this one buys time if the weather turns bad and you need to back pedal on your planting out date.
To prepare single node cuttings, cut a slip from the mother tuber and cut off about ¼” (6mm) above a leaf node (the swollen point where the leaf emerges). In the leaf axil is a bud which will grow a shoot, and just below the bud is a ring of cells that can grow roots. You can trim back the leaf stem, or leave the leaf on. Make the second, lower, cut just above the next node down. You can make several cuttings from one regular slip.
50-cell plug flats work well to grow the cuttings. Push the lower end of the shoot cutting at an angle into the cell, creating an even V with the leaf stem. If a cutting is too tall to fit your cell plugs, you can cut more off the lower end. The new shoot will then grow upwards easily from the bud in the leaf axil.
Keep the trays warm and moist, and plant out after only 18 days, into well-prepared damp soil, with drip tape in place. Delaying planting for 10 days or so is not a problem.
This post includes a discussion of the Single Node Method, in an article in Growing for Market magazine by Andrew Schwerin from NW Arkansas. In warm climates, only use this method if you want really big tubers!
The Hoophouse Bedding Method
I learned this method from my friend and colleague River Oneida, who grew slips for Southern Exposure Seed Exchange. He planted up 4 beds 45’ (14 m) long with three rows/bed in a single-layer hoophouse and grew an average of 4000 slips/week, for a 6 week sales season (24,000 slips), with a peak and bell-curve ends of the season. Caterpillar tunnels could also work.
Store your saved roots at room temperature. From March 1 onward: start the sweet potatoes sprouting indoors in stages, as heated space permits, at 85°F (29°C), and high humidity. Remove any rotting potatoes. When each potato grows ¼” (6 mm) sprouts, take it out of the heated space and replace with new ones. Put the ¼” (6 mm) sprouted ones at room temperature to slow them down for batching with later ones.
In March: Cover the bed area in the hoophouse with a single layer of clear plastic, and kill any weeds that pop up. Four weeks before shipping starts (on April 1 in central Virginia), prepare the beds in the hoophouse. Dig out a flat-bottomed bed 1” (2.5 cm) deep, and set the sprouted sweet potatoes an inch (2.5 cm) apart in rows. One or two sprouts are enough. If possible, don’t bed unsprouted roots
Spread some compost, not lots. Replace the soil you dug out, on top of the sweet potatoes. Add soil from the aisles, putting 1”-3” (2.5-7.5 cm) of soil on top of the potatoes. Not more. Set out drip tape and irrigate regularly.
After bedding, stab holes in the plastic every 4” (10 cm) for respiration. Check regularly, opening the plastic on warm days once slips are visible. In mid-April or whenever you see slips emerging, remove the plastic in the daytime, but put it back for frosty nights Add more soil later to cover exposed tubers if needed. Regulate temperature if you want a faster or slower rate of production.
Some slips will be ready from the 3rd or 4th week of April onwards. If too many slips are ready at any point, pull and heel them in outdoors. Remember to water.
I first wrote this up for an article for Growing for Market magazine, and have included it in my updated slideshow, at the end of this post. It’s a great method for people growing lots of slips (for instance, for sale). It could also be used for smaller amounts, by occupying a corner of a hoophouse growing other crops at the same time.
More Posts on Sweet Potatoes
I have written a lot on sweet potatoes at all stages from propagating our own slips, growing them all summer, and harvesting. My posts include: