Growing lettuce indoors in winter — even year-round — is possible using Peter Burke’s unique technique for growing salad greens indoors.
A very simple idea put me on the path toward growing a year-round indoor salad garden: I wanted fresh salad greens throughout winter. This desire occurred to me one fall afternoon as I was putting my garden to bed and planting my garlic for the following year.
With a pantry, cold cellar, and freezer full of the season’s harvest, the one thing that was missing in my larder was fresh salad greens, there is simply no way to store them. So I experimented with different techniques, and what I discovered exceeded my expectations and eventually became my book Year-Round Indoor Salad Gardening. I can now grow all the salad greens I need for my family of four with a kitchen cupboard and a windowsill, I don’t need lights, special equipment, or a greenhouse.
Growing Salad Greens Indoors: Salad Garden Setup
My wife was used to me harvesting a wide variety of unusual salad greens, so when I started to harvest sunflower greens, pea shoots, buckwheat lettuce, and radish greens, she wasn’t too surprised, just amused. I call the greens “soil sprouts,” because they grow quickly like traditional sprouts grown in a jar, but are grown in soil instead. The soil allows me to grow seeds with hulls, such as sunflower and buckwheat seeds, and maintains enough moisture for the plants to grow, so I only need to water once a day.
If you’re thinking you can’t follow suit because you don’t have a big window with southern exposure, don’t worry — you don’t need it. One of the places I grow my greens is in a small northern window. My daily harvest is about 14 ounces of greens from five small 3-by-6-inch aluminum bread pans. Occasionally I use a larger 4-by-8-inch bread pan when I want a double batch of greens.
Supply List
Most of what you’ll need to grow soil sprouts is probably already in your kitchen.
- I have two boxes with sturdy lids that I use to organize and store all my indoor garden tools. One is my seed box, in which I store my seeds, measuring tools, and cups for soaking the seeds. The seed box must remain completely dry, I don’t place anything wet or even moist inside the box, to ensure good germination of the seeds.
- I keep about a two-month supply, or 4 cups each, of sunflower, radish, buckwheat, and pea seeds, and about 1 cup of broccoli seeds and a few other specialty seeds.
- I also have a few containers of seed mix; I like to mix them together and plant them in one tray. This works well for a small garden for one or two people.
- The other box is for soil and the stuff I use to plant the seeds. I have 2 gallons of a germination mix, sometimes called a “sterile mix,” composed of peat moss, perlite, and vermiculite. This is the very same mix gardeners use to start sets and potted plants.
Steps for Growing Lettuce Indoors in Winter (and Year-Round)
I mix 1 quart of water to 1 gallon of the dry soil mix before planting. I have two 1-gallon plastic containers for the soil mix, a 3-cup container of compost, and a 1-cup container of sea kelp meal. I also keep scoops, measuring spoons, and a few trays for planting. Because the soil mix is moistened, this entire box is damp and thus not good for seeds.
You could use a cupboard or a closet the same way, but our kitchen is small, and having all my tools and supplies in these two boxes allows me to move them into the kitchen for my daily plantings and then back to my office.
With this simple process, you can go from seed to salad in 7 to 10 days, but don’t mistake your indoor salad garden for a “toy garden,” it’ll be deceptively productive. If you were to plant an acre of these little trays, the annual yield would be far more than you could eat! If you’re considering reducing your carbon footprint or eating local, this is a simple and rewarding way to accomplish both.
My daily routine starts with soaking the seeds that I plan to grow. In fresh water, I soak 1 tablespoon each of sunflower, pea, radish, and buckwheat seeds, and 1 teaspoon of broccoli seeds. This is my daily minimum, and it will yield about 14 ounces of cut greens. The seeds should soak from 6 to 24 hours before planting. Even the smaller seeds, such as broccoli or mustard, should soak that long. I use 3-ounce plastic cups or small glass Mason jars for soaking. Whatever you use, it needs to be waterproof, I once made the mistake of using paper Dixie cups that fell apart overnight. Fill the cups to the brim, because the seeds will absorb a lot of water. My habit is to soak the seeds in the evening while I plant seeds from the day before and water my trays of greens. Then, I plant those seeds the next day. If your seeds have been soaking for 24 hours and you can’t get around to planting them, just pour the water off and let the seeds start to germinate in the cup. This isn’t ideal, but it will still give you a good crop.
Once the seeds are soaking, make sure your soil mix is moist; use 1 gallon of dry soil mix to 1 quart of water. When the soil is ready, I fold a few sheets of newspaper to use as a cover for each tray of seeds. The wet paper keeps the seeds moist better than the soil alone does, and it’s cleaner than wet soil. Plus, the wet paper helps to block light from getting to the germinating seeds too soon.
When you’re ready to plant, put 1 tablespoon of compost and 1/2 teaspoon of sea kelp meal in the bottom of the tray. Then, fill the tray with the moistened soil mix, up to 1/4 inch from the rim. You’ll need a little space for the seeds and for room to hold the water while it soaks in. Then, level off the soil so it’s even. Plant the seeds by dumping them on top of the soil; don’t bury them, as they’ll be covered with the wet newsprint instead.
After they’re planted and covered, move the trays into a warm, dark place for the next four days. I use the cupboard over my refrigerator, which is warm and dark. I also have a cupboard by our woodstove that’s cozy and dark. You could use a closet or even a cardboard box in a warm spot on the floor. If you don’t have a really warm place, this method will still work, it just might take five or six days for the sprouts to grow up to an inch high.
All these steps combine to force quick germination and growth. It may be counterintuitive for gardeners or farmers who generally put seedlings into the light as soon as they germinate so that their stems are short and stocky. In contrast, you’ll be encouraging these seeds to grow long stems to reach for the light before putting them on a windowsill to get some sun.
Harvesting Salad Greens
When the greens poke up about an inch high and the wet newspaper cover is sitting on top of the still-yellow leaves, I call it the push-up day, or the final day of their stint in the dark. This is the day that you’ll want to move trays into the light. I have a freestanding shelf that’s 20 inches wide, 12 inches deep, and 72 inches high, and it has a cupboard to keep the trays in the dark and four shelves above the cupboard for the trays to turn green and grow. This shelf illustrates the absolute minimum amount of space you’ll need to grow enough salad greens for four people to have a good-sized tossed salad every day.
When the salad greens are about 6 to 10 inches high, they’ll be ready to harvest. I prefer scissors, but a sharp knife works well too. First, pick off any remaining seed hulls, and then cut the greens about 1/4 inch above the soil line. I place the cut greens in a shallow container and rinse them in fresh water. By covering the greens with water, any remaining seed hulls will float to the surface and dump out over the edge of the container.
Chop the harvested salad greens into small pieces, about 1/4 inch at the stem end and longer at the leaf end. The stem ends are usually tender, but the longer they grow, the tougher the bottom of the stem can get. Buckwheat lettuce, radish, and sunflower greens are tender enough to top a sandwich without cutting them, but I like to chop them for use in a salad.
Most local farm stores don’t carry organic seeds in 2- or 4-pound bags, they usually only sell the ounce packages, which are too expensive for this purpose. I’ve used seed stores online, such as Johnny’s Selected Seeds, High Mowing Organic Seeds, and Handy Pantry, and I have my own online store, The Daily Gardener. Many catalogs now offer seeds for sprouts, but I caution you to buy a small amount to start with to make sure you’re happy with the germination rate and the size of the soil sprouts before you buy a large quantity of seeds.
That’s all there is to growing lettuce indoors in winter. This method for growing an indoor salad garden has surpassed every expectation and hope I had when I first started this project after a moment of inspiration.
An avid gardener, author Peter Burke has been teaching garden classes since 2006. He also started The Daily Gardener, a shop that provides organic seeds for indoor gardening. He lives and gardens with his family in Calais, Vermont.
