by Leigh Mills
We have a small, unheated greenhouse on our off-the-grid homestead. It’s attached to a south-facing section of our house, and we’ve been growing salad greens, basil, and other plants in it for about 7 years. It’s not a fancy greenhouse, but it’s built well enough that I can grow salad greens during the cold, dark months of the year; especially when I pamper my lettuce.
I learned the basic principles of growing winter greens from reading Elliot Coleman’s Four Season Harvest several years ago. I grow cool-loving plants and use row covers in the greenhouse when the outside temperatures dip below 10°F. Elliot’s Four Season Farm is in Maine and some of his research for that book was from studying farms in France. I live in the Rocky Mountains, at 8400’ altitude, in a high desert valley and do things a bit differently to enjoy eating fresh lettuce from my unheated greenhouse, especially when the outside night temps have been below zero for two weeks in a row.
In addition to using plastic row covers, I also use straw mulch and if it’s really cold at night, say -10°F, I’ll use blankets as the last layer. Having the greenhouse attached to the main house makes a big difference, too! Our greenhouse is made from simple materials like rough-cut 2×8 wood, single layer polycarbonate sheeting and a layer of 3.5 mil plastic sheeting on the inside. There are two large, raised growing beds filled with organic matter which hold quite a bit of thermal mass and help keep the temperatures stable. The little greenhouse also has two doors in the winter time; a screen door on the outside and a heavy wooden door on the inside. All these elements help create a warm enough greenhouse that can grow greens throughout the cold dark months.
The maintenance routine definitely takes some attention, and this is where the salad greens get pampered. I don’t need to do much until the nighttime outside temps start to hover around 10°F. At that point, I’ll install the thin metal hoops and get the plastic ready to cover the beds. I’ve been doubling the plastic because I’m reusing it from the bigger outside beds and don’t want to cut it down. I’ll cover the beds at once when the sun goes down and uncover them in the morning. When the outside temps start hitting zero degrees, then I’ll add some dry straw on top of the plants to give them a little more insulation.
I had to work a bit harder when we had two weeks of -10°F nighttime temps in December. I added even more straw on top of the hardy plants and a blanket on top of the plastic as a last layer. Having a lot of straw on top of the salad greens during the day isn’t the best situation for their growth, so I would skim a bit off in the morning and replace it for the evening. Yes, I’m a bit obsessive, but this is food and future seed. Luckily, I don’t need to do a lot of watering during the short, cold days; but I do remove the straw so it doesn’t get wet and replace it after I water so it will keep the plants warmer at night.
I don’t grow salad greens every winter, as you can see why. But I’m growing them this year, and am enjoying eating the fresh greens. Where there’s a will, there’s a way. Have a Happy New Year!
Leigh Mills has lived and gardened in the San Luis Valley since 2002 and written the “As the Worm Turns” column for almost 4 years. If you enjoy reading her monthly, visit her gardening and seed saving blog to view color photos and read journal entries filled with tips about high-altitude gardening, seed saving, food preservation, yummy recipes, and off-the-grid, homestead living: The Infinite Bee (theinfinitebee.com).