By Roberta Bailey
For the past four winters, I have eaten fresh kale and other greens every day from a growing bed in my attached greenhouse. Often I stop on my way to work and pick greens for lunch. If not, I stop on my return and pick part of supper. Just walking past the lush growth on my way in from the snowy or bitter outdoors nourishes my soul.
Unlike many year-round harvest systems that are being taught lately, I grow my plant to full maturity in outdoor gardens, then bring the full-grown plants into the greenhouse in early October. All of the plants that I bring in are cold hardy and thrive in cooler weather. By growing them in their preferred habitat, I don’t have to bother with watering the greenhouse or keeping it cool by using shade cloth.
Because the floor of the greenhouse is stone, I built a 2 foot-deep 10 by 2 foot growing bed on posts. The bottom foot was filled with hay and corn stalks and compost, the top foot was filled with compost and garden soil. The bed was placed against the house where it would be warmest. This location also left the option of making an inner cold frame that would butt against the house wall, including two windows that could open to the house for added heat. I found that by choosing very cold hardy plants I never had to build the inner cold frame, but it was an option that would be useful if I wanted to overwinter more tender crops, especially with seed saving in mind.
To bring in plants, I left the top foot of the growing bed empty, then went out to my garden rows and dug the choicest plants with root balls as intact as possible. These were set in the growing bed, then as each row was “planted,” I would fill in around the root balls with compost and garden soil. Smaller plants such as spinach and cilantro, can be transplanted between the rows of taller plants, such as kale. I nestle the smaller plants into individual holes, as their root balls are small. Shady or rainy days plus thorough watering help the plants adjust. Some dieback will occur, but not much.
Kale is by far the most successful plant for this type of overwintering. When the greenhouse dipped below zero inside, the kale was brittle and would shatter when picked if I was not careful. As soon as the temperature rose above freezing, it was back to normal with no sign of wilting. White Russian kale is the bushiest, hardiest kale I have found for the greenhouse. Once March comes, it puts on growth from every bract, becoming quite prolific. Konserva and Winterbor winter well but are less prolific.
Spinach, cilantro, parsley, mustard-spinach crosses and mache also overwinter quite well. Spinach lays flat in the coldest winter temperatures but perks right back up once it thaws. All five will die in my greenhouse in the bitterest of winters, but have thrived in the last two Maine winters.
The plants maintain themselves until early February, when the days start to lengthen, then they start to grow noticeably. By March, they are bushing out aggressively. The kale starts to send up tender broccoli-like flower shoots that are delicious. I sometimes seed new crops in February, such as lettuce, mache, spinach, mustard or cilantro, between my kale plants. They germinate within a week or so. Weeds brought in with the root balls also begin to grow. I relish the dandelion and chickweed, actually making sure that some come into the greenhouse, so that I have a few early spring tonic greens.
I see the greenhouse as a potential aid in raising seed crops of brassicas in Maine. The kale plants could be set back outside, as could broccoli, Brussels sprouts, etc. An outside double greenhouse built directly over a row of seed crops (which may also have to be mulched with straw or hay) also could enable northern seed savers to save tender cole crop seed.
Aphids can become a severe problem in a greenhouse in late March. I spray with insecticidal soap and have heard of a molasses and water spray that deters them as well.
My greenhouse is glass. Part of it is constructed with double glazed sliding glass door panels. These are great, though their seals can break after a few years, causing fogging. Part of the greenhouse is constructed with recycled windows, doubled up, and set snugly into wooden upright supports. These have never fogged. The beauty of glass is that you buy it once, baring casualty, and there is no plastic to replace and dispose of every few years. We do sweep the glass after heavy snow storms.
Aside from healthy greens all winter, and plants to lift a winter weary spirit, the greenhouse buffers the cold on the side of the house and actually adds heat most months of the winter. From mid-February on, we open the door to the house on sunny days and let the heat flow in. Many a day I have dragged a chair out there and read or napped or wrote my MOF&G columns, pausing only to pinch a sprig of parsley before turning the page.
About the author: Roberta is a dedicated seed saver and a member of the Maine Seed Saving Network.