Here in Western Massachusetts, with its short, cool growing season, a backyard greenhouse is a real boon for those of us concerned with providing our families excellent food, even when supply chains are shut down during a time of crisis. We have spent three years figuring how to maximize the relatively small interior space of our rectangular, rigid-walled greenhouse in an efficient manner.
Early on, we realized there were steps we could take to increase the interior temperature during our cold, windy winters. My husband rescued an old thermal pool cover that was headed for the landfill and cut out sections to fit against both the north and west sides. By doubling this cover, we now had both a wind break and heat sink that held sun-generated warmth. He also made a double 6 ply plastic cover that is raised during sunny days but can be lowered to about a foot above the ground at night. This essentially makes an interior cold frame that protects crops from frigid night air. We added a stone walkway down the middle of the greenhouse that captures heat as well as keeps the area cleaner. Our final step was to ring the exterior of the greenhouse with bales of hay, stacked two deep. It is an easy matter to move the hay away from the door so we can enter as long as we keep the area free of snow. On the coldest nights, we bring out the day’s ashes from a wood stove, captured in a metal bucket. With these measures in place, we have never had the ground freeze on the interior, in spite of nights that dip to -20 degrees.
The next step is to ensure that the soil inside is as healthy as possible. This means liberal applications of compost and bi-weekly applications of a weak fish emulsion fertilizer.
Finally, we developed a plan of crops and crop rotation that makes the best use of our available space. We were looking for crops that provided maximum nutrition and dietary bulk. We were surprised by some of the things that did quite well.
In mid February, we plant several varieties of lettuce seeds. They start slowly but by mid-March, we harvest a salad a day. This was an early spring for us and I can’t guarantee such good results every year. We started our seedlings inside in early March. My early April, we were able to harden them off in the greenhouse. We have never had such healthy and vigorous starts. As the lettuce starts to bolt in the heat, we will be removing those plants and replacing them with some miniature melons, something we could never grow in our climate, as well as root crops such as carrots, turnips and beets. We ate turnip and beet greens late into January and we were pulling the roots throughout the winter as the ground never froze. We planted hardy greens such as bok choi, tat soi, chard and spinach in August. By October, we were eating the first of those greens and they continued to produce well into winter.
As the root crops develop below ground, a shelf above hold individual pots of salad greens and cherry tomatoes grow in suspended planters. We started these later than our garden tomatoes and we were enjoying fresh salad tomatoes weeks after frost had done away with the main crop. We did not have luck growing bush tomatoes in the soil. We got all vine and no fruit.
Other important considerations are water, pests and heat control. Greenhouse plants need a lot of water. In early spring, I water seedlings every day. As it gets warmer, it is not unusual to water twice a day so having a source of water nearby is terrific. A rain gutter that drains into a bucket would be helpful. Our greenhouse has two roof vents that have to be opened early in the day, before the sun gets too high. Unopened, the temperature can reach 110 degrees by 10:30 in the morning, a temperature that will fry any tender plant. Even in mid-winter, the greenhouse is so warm we are able to eat lunch out there. Some greenhouses have solar operated vents that open and close as the temperature fluctuates. It is an upgrade we wish we had invested in. We do have a black shade cloth to keep the interior cooler in extremely hot weather. This is seldom necessary in our climate but a more southern location would find that useful.
Pest control is vital as aphids can be a real problem. We find that a squirt of soapy water followed by a clear rinse does a good job of keeping them under control although at one point the infestation was severe and we had to pull out the Asian greens, which were the biggest problem. If you plan to bring any plants from the greenhouse inside, check closely for these pests.
We have been so satisfied with the productivity of our greenhouse that we are planning to invest in another one, further enhancing our ability to feed ourselves throughout and food, energy or weather crisis. – Kathy Harrison, author of Just in Case
