One of my greatest greenhouse fantasies in the early days was having fresh, beautiful tomatoes all year long. I know it doesn’t seem like much, but I just couldn’t bear going back to those plastic, tomato-like things they sell at the market. They sure look like tomatoes, and on a good day, they smell sort of like tomatoes, but man, they don’t taste like them. So when my first greenhouse went up, I was determined to have veggies all year. And I did, eventually. Now, when I go to the market, I glance at those pale, tomato-like things in the produce department and am so thankful for my greenhouse and all it can do for me.
Your greenhouse can work for you, too, if you’re a veggie-growing gardener (I’m not here to judge you exotic flower-keepers, my African violets would not approve of that kind of behavior). With the application of a little heat and light, you can easily keep warm-weather vegetables going through the deepest winter. If your greenhouse is more basic, cool-weather crops may be a good choice—lettuces, brassicas, root veggies and onions do well as long as you can keep the frost off of them.
I’ve made a list of the top five vegetables you should be eating this January, and we’ll talk a little about what each will need to thrive in your greenhouse. Armed with this information, you can now go boldly into your indoor vegetable adventure!
Did you really think they would be anywhere but number one? A perennial favorite of gardeners everywhere, tomatoes are beautiful in the greenhouse provided you keep them in large enough containers. Five gallon buckets with a tomato cage stuck inside work nicely and keep the vines from being a huge mess. Bear in mind that tomatoes must be pollinated to fruit, but a gentle tap on flowers in bloom is often enough to make it happen. Keep tomato-filled zones heated to between 60 and 80 degrees Fahrenheit at all time for optimal fruiting and train your plants well to help prevent disease. Both determinates and indeterminates can grow in a greenhouse, just make sure they have enough space to grow to maturity.
Cousins to the tomatoes, peppers are excellent choices for indoor growing. As long as they’re kept warm, pepper plants are fairly flexible and can tolerate a bit of abuse. Like tomatoes, they must be pollinated and the same tapping technique works for both. Peppers need large containers, but most won’t reach the size of tomato vines, so look for pots that hold at least three gallons of growing medium. A tomato cage can help keep the plants contained, but if you pinch more bushy varieties, they should be able to stand on their own with only minimal staking. Go hog wild with your peppers this winter and add a chocolate or purple bell into the greenhouse mix!
Ah, cucumbers! These lovely pre-pickles are great for winter salads and there’s an amazing selection of varieties to choose between. When growing indoors, bushing cucumbers are best, simply because they’re naturally small, but if you have a very tall greenhouse, you may be able to trellis and train vining cukes enough to keep them tidy. Pollination is trickier in cucumbers and their relatives because they have both male and female flowers. Males typically appear first and in clusters on the vine. Females appear individually while males are open, but often open last—they will have a three-lobed structure in their centers.
Take a small paintbrush to the male, twirling it around the cone in the center of the flower to collect pollen before moving your brush to the female and carefully painting the pollen onto the lobes. You’ll know you succeeded within the week because your flower will shrivel as a small cucumber begins to take shape behind the flower petals. Cucumbers need warm temps like tomatoes and peppers, so keep the heaters on. In fact, these three veggies work well together in a heated greenhouse.
For those of you without heated greenhouses, lettuce is a perfect winter crop. In fact, leaf lettuce gets all sorts of bad if temperatures exceed about 70 degrees, so an unheated winter greenhouse is practically ideal. Unlike warm-weather veggies, the part of the lettuce we eat are the leaves, so you don’t have to bother with pollination, making lettuce a great crop for beginning growers. You don’t need a fancy pot when growing lettuce, but do make sure to start your lettuce from seeds in a container that’s about four inches deep—adding a heated mat will help with germination. If you sow seeds thickly, you’ll be able to harvest baby greens as you thin your plants, giving your lettuce planting lots of mileage. Lettuce may not seem like an exciting greenhouse vegetable, but what you can grow will be much better than what you can get in the market during the winter.
5. Root vegetables
In a lot of areas the soil is too rocky or hard to grow any kind of root vegetables successfully without a great deal of work. Gardeners in these areas have long experimented with growing their carrots, radishes and other root veggies in containers on the porch to save the back-breaking work it would otherwise require. They perform wonderfully in containers, provided you choose one deep enough for your longest root vegetable—many can even be grown together in one big tub. Like lettuce, root vegetables are best when it’s cool, but not freezing. If you sow a row of seeds each week, you’ll have root vegetables popping up fresh all winter!
These are just a few of my favorite greenhouse veggies. If your greenhouse is zoned, by all means try to grow both cool and warm-weather vegetables in the same structure, but if this is your first go at winter growing, you may want to focus on one group. You’ll be amazed at how productive a greenhouse can be in the dead of winter and the fresh vegetables on the table are a great bonus. Before you know it, you’ll be ready to branch out into much more difficult edible plants like small tree fruits and melons.