Winter vegetables and greens are a joy to grow because they are tolerant of cold weather and thrive in the spring and fall. If you like the idea of frugal living with a garden, wait until you start growing and harvesting cold weather vegetables in the off season.
Cold weather vegetables include crops like kale, cabbage and broccoli that can be grown successfully year-round, even if you don’t have a heated greenhouse. These vegetables can be grown, or at least harvested in cold weather, so we have an opportunity for a year-round harvest. What better way to save money on groceries?
Thanks to the research and focus of a handful of tireless gardeners, breakthrough methods have been developed for a year-round harvest of winter vegetables. Individuals like Eliot Coleman provide us with insight and experience that allows us to convert cold weather crops into true winter vegetables that allow us to feed ourselves all year long, without necessarily resorting to canning, drying and freezing. What better news for gardeners?
In most of the U.S., vegetables can be grown, or at least harvested, in any month of the year without the need for a heated enclosure. In some of the northern areas, a harvest of winter vegetables will require an enclosure and row covers, but these don’t have to be fancy or expensive. They can be homemade like mine. And, they are long-term investments in good eating and good health.
Kale has always been known for its resistance to cold weather. It thrives in cooler weather and can withstand frost like a snowman. It tastes sweeter after a good frost, and it can even be harvested in the winter if you dig it out from under a cover of snow. Imagine how cold hardy this winter vegetable would be if you give it the protection of a simple enclosure.
Crops Suitable for Winter Harvest
If you are going to grow and harvest in the winter, what exactly can you grow? The varieties of winter vegetables are many, but they don’t include things like tomatoes, melons, eggplant and peppers. These plants love warm weather and aren’t suitable for a winter garden.
Let me say that again. There are vegetables that can withstand below freezing weather – even weather that dips into the teens and lower. If they are still with us after a night in the teens, you know these are winter vegetables.
Late Fall to Early Spring Crops
These crops include peas, radishes, kale, Brussels sprouts, cabbage, broccoli, onions, lettuce, beets, turnips, salad greens, Swiss chard, kohlrabi, turnips and collards. These vegetable aren’t necessarily suited to planting and growing in the winter, but they will allow a harvest in much of the winter or the months that are considered off season to the normal summer gardener.
You probably don’t buy this many types of produce at the store on a regular basis, so having this sort of variety available during winter should satisfy even the most finicky of vegetable eaters. A quick Internet search will reveal many seed companies that publish a catalog just for those who want to grow “off-season.”
Enclosures and Row Covers
A simple enclosure is necessary to stretch the season. It will capture heat from the earth and sun to warm things up during the day to promote a kinder and gentler environment for winter vegetables. Cold frames, row covers and hoop structures can be used in the garden. If they are used to create a “greenhouse within a greenhouse” they promote an even more sheltered environment.
Late one March we transplanted 3 types of lettuce, along with endive, arugula, snow peas, snap peas and vit (corn salad). This was a little over 2 months ahead of the time we normally could transplant them into the unprotected garden. The idea was to get a head start on the cooler weather crops. Even though our greenhouse has some leaks, it still retains heat, even though it only has a single layer of glazing.
Since our planting beds were not set up for row covers, we used quart and gallon glass jars to provide a “greenhouse within a greenhouse” for the little transplants. These are also called a cloche, and this article explains how you can make a cloche from just about anything. Temperatures dipped into the teens and single digits a few times. The coldest weather nipped some of the lettuces and greens, but most of them survived just fine. The early plantings provided a good head start, and one month later we were harvesting our first salads. Nine weeks later, we were still harvesting enough greens for about 8 generous salads a week. Our experience suggests that we need to plant at least twice the number of lettuce plants to provide a nice salad every day.
This year we plan to plant an assortment of lettuce and greens in the fall that should allow us to harvest winter vegetables from the greenhouses. With the aid of row covers and active solar heating during the day, we should be able to apply our early spring experience to the late fall and winter harvest with even greater success.
We don’t fight Mother Nature, but we do make full use of our greenhouses. They provide winter vegetables during the colder months when they would normally sit idle. Think of it as asset management. We have an asset, and it can either work for us, or sit idle and be worthless for half the year. We’re making it work for us.
Active solar heating in the greenhouses helps us push the limits for some of the cold sensitive plants and stretch the harvest time for some cultivars. We might add a little heat occasionally, but we don’t try to grow summer vegetables in the winter. That is too much like work. If our experience during spring is any indication, we will expect growth in the late summer and fall and that harvest of winter vegetables in the short days of December through March.
Watering During Winter
Water will be stopped when we start to get consistently cold temperatures. This helps avoid killing the vegetables when a hard freeze sets in. It is my understanding that water in plant cells freezes and ruptures the cells with a hard frost. Backing off on the water late in the fall should help avoid this problem. If your winter vegetables have moisture from the fall, but no added moisture during the winter, they most likely will last much longer even in temperatures well below freezing. My lettuce plants survived temperatures of about 12 degrees, and didn’t show any signs of problems. They like it warmer, but are capable of making it through nights that would kill most other plants.
You should harvest during the warmth of the day in spring. If you don’t allow the plants to warm up for a while, you might be harvesting mush in the middle of the winter. Several hours above freezing is needed to help the plants to recover from the deep freeze.
Broccoli and kale have an affinity for cold weather. I planted both of these cold weather vegetables in the spring and they began to grow rather well in the cooler weather and lengthening daylight. Once the hot days of summer set in, they slowed their growth to a crawl. They were in a kind of suspended state waiting for cooler weather.
When the summer vegetables were giving us their last fruits and showing signs of stress because of the consistently cooler days and nights, the broccoli and kale started growing again as if someone had turned on a switch. How nice it was to see something in the garden that appreciated cooler weather. Oddly enough, these and many other winter vegetables enjoy cooler weather and can tolerate some frost out in the open.
Over Wintering Root Crops
Another thing you can do to provide food in the winter is identify root crops that can over-winter or at least store better when left in the ground as winter sets in. Varieties like onions, carrots, parsnips and rutabagas can be left in the ground longer and harvested throughout the winter by digging them up. Some winter vegetables are meant to winter over just fine for a spring harvest.
One spring while rototilling the garden, I hit upon a couple of onions that hadn’t been uncovered during the harvest of the previous year. They popped up onto the soil as the blades of the rototiller dug them up. I examined them and found them to be in excellent shape. This year I’ll plant onions intentionally for a spring harvest.
If you have an enclosure, you’ll do even better at keeping an underground harvest ready to eat. Your crops will have the protection from extreme cold and wind. More importantly, you’ll have a protected area in which to harvest. It is no fun digging out in the garden when the wind is blowing snow all around you.
My Experience with Winter Vegetables
I planted some seeds for winter vegetables in a greenhouse during the fall and waited for winter. My only precaution was to use a row cover over the turnips, bok choy, chives, lettuce and Swiss chard that had been designated as the “guinea pigs”.
Each of the crops were planted in separate raised beds and covered by the same single layer row cover made of 6 mil poly. The raised beds were steel half-drums, so they gain energy readily, but also readily give it up. Not the worst but certainly not the best scenario for growing winter vegetables. The greenhouse still had its top vents open reducing its ability to retain heat. The snow even piled up on and around the row cover inside.
Here is the upshot of the experiment; as of early December everything survived just fine. Even after 36 hours at below zero temperatures. I’m talking not just below freezing (32F), but below zero – well below zero. Our lowest temperature was -14F.
Some of the plants looked like they took a little beating, but when temperatures came back above freezing for a day, I harvested the bok choy and some of the turnips and they looked just fine. The ground around the plants was frozen solid, but the plants looked just fine. That is simply an impressive performance by winter vegetables. There is no other way to look at it.
The lettuce seedlings were still trying to grow under their small poly covering. I was truly amazed and would have been highly skeptical of anyone claiming something similar if I hadn’t witnessed it myself. With results like this, we know that year round vegetable gardening is entirely possible here in (barely) zone 5. Just think of the results if we were to use double row covers and cold frames under row covers within the greenhouse?
Clair Schwan is an experienced vegetable gardener with open sun gardening beds and three quality greenhouses of his own design and construction. He grows over 100 varieties of vegetables and provides fresh produce year-round for himself and his family.