Growing and Storing For Winter Markets
Becky Maden works in Vegetable Nutrient Management for the University of Vermont Extension. At the time of writing this article, Becky was the Assistant Farm Manager at Intervale Community Farm (ICF), a thriving member-owned CSA farm in its 21st season of growing organic produce in Burlington, Vermont. Becky has worked on several diverse vegetable farms throughout the country and around the world. When she's not on a farm, Becky loves to travel, write, bike, run, ski, and cook bounteous meals with glorious produce.
For the past week, I’ve been staring at a small crate of watermelons in our walk-in cooler, tucked aside on our “staff” pallet. Each time I pass it, I wince in disbelief. My favorite gluttonous time of the year is over. No more dashing through the field, tossing melons slippery with dew, shouting out the numbers of tossed and caught melons. No more giggles as a melon comes towards me too hard and slides between my belly and arms, knocking away my breath and dropping to the ground with a thwak and a crack. No more sticky fingers and dripping chin as I cannibalize the dropped melon, stuffing the rich fruit into my mouth while running with my arms outstretched for the next watermelon careening through the air.
Summer, in its sticky, harried, gorging glory, is over. Tossing cabbages and butternuts comes with its own set of giggles, but there is admittedly far less joy in dropping either of those crops. But what the close of watermelon season truly means is that it is time to turn my thoughts towards fall, winter, and early spring crops. Imagining baby spinach covered in remay, with the ground cloaked in snow just a few months away just doesn’t hold the same allure as flipping through seed catalogs in January to pick out tomatoes and peppers and eggplant varieties. However, a little forethought about winter growing can provide economic opportunities, job security, continuity of relationships with customers, and exciting learning opportunities for a vegetable producer - as well as delicious food all winter long.
Although it is alluring to think of winter growing as simply planting greens that will be harvested throughout the long, cold months of the off season, it is important to distinguish between the two main ways of extending the farm season:
Appropriate variety selection, handling, and storage of crops for sale throughout the winter. This includes roots, squash, cabbage, and a variety of other brassicas.
Growing a selection of fresh greens and herbs that can be harvested for as much of the winter and early spring as possible.
In this article, I’ll outline the bones of a winter cropping system based on my experience at the Intervale Community Farm (ICF). Your own systems will be largely defined by your available storage, your markets, and the square footage of growing space you have under cover.
- Make storage crops a cornerstone of your season’s crop plan.
Roots, cabbage, and other storage crops don’t quite have the same glittery appeal as winter in-ground production does, but to discuss season extension without describing the dependence many of us have on stored crops would be disingenuous. The bulk of our farm’s winter share depends upon these crops, which we incorporate into our regular season’s crop plan and harvest schedules. Planning to have enough of these crops requires focused attention even during frantic summer months. On our farm, we make a concerted effort make sure that fall roots and brassicas are carefully tended, and that our potatoes, onions, and squash are abundant enough to serve both our summer share and winter share customers.
- Select varieties that store well.
We are always on the prowl for high quality vegetable varieties, particularly as we farm organically in close proximity to many other vegetable growers and a spectrum of associated plant diseases. For storage crops in particular, we select carefully for flavor, disease resistance, and keeping quality. For example, although we favor Ya-Ya carrots for our summer and fall production, we prefer to grow Bolero for our storage carrots. The flavor of Bolero improves in storage while the integrity of the carrots holds up for months. Likewise, we are still searching for the perfect storage cabbage; any disease we find on cabbage in the field accelerates once in storage. Black rot and thrips are two problems we struggle with regularly, and each season we trial several cabbages to see which performs best for us in storage. Each year it is ever clearer to me that good variety selection combined with clean field conditions translate into high quality storage crops.
- Make the most of your available storage conditions.
Farmers and gardeners store food in a wide variety of ways, from root cellars to basements to crammed refrigerators to cool-bots to large walk-in coolers. Ideally, vegetable growers would have multiple storage rooms and coolers with different temperatures and humidity levels. But few of us are at a scale or profit margin to justify these investments, so we all must choose to work with what is realistic. At ICF, we’ve had great success with two storage climates; one, our walk-in cooler, which we keep at 33° F and at 90% humidity, and a “squash” room that we keep at 55° F with minimal humidity. We would love to have a separate space for potatoes – which would be slightly warmer than our walk-in cooler (around 40° F, with 90% humidity). There is a wealth of great information on storage conditions for winter crops; but with a little attention to the details, you can eat and sell delicious food all winter long.
While storage crops are the bread and butter of winter vegetables at our farm, we balked at the idea of offering our farm members a winter share until we were confident that we had the capacity and the expertise to offer them freshly harvested greens for most of the winter. Our winter share CSA members come every other week between mid-November through mid-March, and at each pick-up they leave with around 20 pounds of delicious, high-quality vegetables. But no item gets more comments or appreciation than that small bag of fresh spinach that they carefully place on top of their heap of roots, cabbage, and squash. So we indulge ourselves and our members by planting all six of our unheated hoop houses and one greenhouse (nearly 11,000 square feet total) into winter greens.
- Select varieties for winter growing conditions.
Winter growing comes with an entirely different set of challenges for the vegetable grower. Before the seeds even go into the ground, it’s important to consider the challenges that crop is likely to face as it grows in a time of decreasing light, cooling temperatures, and frequently high humidity. As in any greenhouse environment, good ventilation and consistent temperature control is key; however, during a time of year that is climatically challenging, this can be hard to achieve. At ICF, we’ve had the most success growing spinach in our hoophouses, as we’ve found that it is very cold hardy and tolerates a broader range of conditions than greens like arugula or baby lettuce. In addition, we find that it is easy to harvest, yields well, and is a crowd-pleaser for our members.
More and more spinach varieties available are specific to winter growing. We’ve had wonderful success with both Regiment and Renegade spinach. Both varieties are resistant to Downy Mildew races 1-7, which is a disease that is commonly found on hoophouse spinach.
Although spinach is the reliable backbone of our winter greens production, we also plant a mix of specialty greens for our November and December harvests. These include arugula, mizuna, tatsoi, red Russian kale, and red giant mustard. We also seed some baby lettuce – again, downy mildew resistance is crucial, so Red Oakleaf or Oscarade are good choices for red oakleaf for winter production. We find that baby lettuce is the least tender of the greens we seed, and also requires the most air circulation, so we tend to rely least on a significant yield of lettuce. Instead, we use it for color in our mix with other greens.
Other crops we’ve experimented with for winter growing include scallions, cilantro, mache, claytonia, and hakuri turnips. All of these crops have proven tasty additions but with yields too small for the purposes of our winter CSA distribution. In addition, we’ve found that the turnips and scallions require a longer growing window that we have since our hoophouses are in tomato production right through mid-September. These crops would be a good fit for a grower with the right markets that offer the right price.
- Tailor your growing conditions to winter production.
While disease resistance, cold tolerance, and yield determine our variety selection for winter greens, the particular circumstances of our chilly climate affect our planting layout. First and foremost, we’ve learned to plant our greens less densely than we do in our summer field plantings. This helps with air circulation and disease prevention. Stand density isn’t too much of a concern for us since we don’t have any weed pressure and we harvest all of the winter greens by hand. Furthermore, we’ve found that our yields and leaf size remain good even though we dial back the seeding rate density by about 1/10 of what we do in the field.
We seed all of the winter greens with a one row Planet Jr. We use the middle of the hoophouse for two wider beds (40”) with a one foot walkway between them. The edges of the hoophouses are colder so we leave a margin along the base board, then seed a 30” bed with the hardier greens. We leave a little more space between seeder tracks than we do in the field, once again to promote air circulation for the greens.
We leave the crops uncovered until the weather turns chilly; then we place wire hoops every 4 feet along the bed and cover with remay. Ideally, we would ventilate the crops every day by removing the remay and cracking the roll up sides of the hoophouses; in reality, unless it is sunny and warm, we manage the greens as little as possible during the quiet winter months of farmer down-time. If a serious cold snap arrives (temperatures below 15° F), we will place a second layer of row cover on top of the first; the advantage is a few degrees of frost protection, while the disadvantage is more light interception. Once February rolls around, we are more careful about ventilation on sunny days – the strength of the sunshine can be surprising that time of year, and it’s important not to have dramatic temperature differences between the daytime highs and nighttime lows.
- Time Your Plantings CAREFULLY!
Perhaps the easiest thing to overlook with winter greens is planning the seeding times appropriately. At our farm, we have a solid crop plan that dictates the seeding and transplanting dates of our crops, but every year, the fall-seeded greens are a bit of an afterthought. And each year, the end of August rolls around and I find myself pawing through books and old field logs wondering: exactly when did I seed winter greens last year?
Planning precisely for winter greens is critical to maximizing your yield potential from the greens. Shifting day lengths create a bell curve effect such that planting a week late in the fall can mean an entire month of missed harvests in the winter. At ICF, we find ourselves annually navigating the balance between maximizing our hoophouse tomato production season and wanting to clean out the hoophouses to prepare them for winter greens. We’ve found that planting early determinate tomatoes in half of our hoophouses has been a great strategy for an early bounty of tomatoes that ends in August, allowing us ample time to clean and prep the houses for fall seeding.
Our first seeding of spinach and mesclun greens is towards the end of September; usually around the 20th. We aim to have our first harvests towards the end of November, and we hope to pick from these houses right through early January.
We do a second round of seeding in early October – around the 2nd for more mesclun greens, and around the 7th for more spinach. These seedings aim towards an early February harvest that will last through the end of March. As with all agricultural acts, the weather can wreak havoc on the best laid plans; a sunny, warm winter like 2011-2012 will accelerate growth (but allow for multiple harvests); a snowy, cold winter like 2010-2011 will slow down the growth and add extra challenges (like tons of snow removal and fears of collapsing hoophouses).
- The limiting factors…
Water is extra tricky in the winter growing scheme. On our farm, we don’t have frost-free water available in our hoophouses, but we’ve found that watering early to get the plants established is usually adequate. Sometimes we find that a sunny, warm February can make the leaves leathery if they don’t get any water, so we try to take advantage of one or two breaks in the winter weather to give the greens a little bit of water. But for the most part, it’s important to remember that the plants are limited by available light and are not actively photosynthesizing or transpiring. Excess water will only add to disease pressures
Adding heat and light are options for growers with heated greenhouses and markets that justify the additional inputs. At ICF, we’ve determined that our existing CSA market as well as our ethic of minimal environmental impact has kept us from exploring greens production in a lit and heated greenhouse.
Our future plans at ICF include expanding our winter greens production. We’ve been impressed with how much more yield we get from our unheated 30x96 greenhouse versus our 14x96 hoophouses, so we plan to build more of the former. We’re looking forward to exploring and refining our selection of greens, our planting dates, and our production methods in order to have high-quality harvests all winter long. And although I’ll dream about watermelon during those dark January days, eating fresh greens from our own soil on a snowy, cold day is a remarkably luxurious treat.