Backyard Greenhouse

Here's my Northern Light Greenhouse. It's weathered 14 Vermont winters and is still going strong.

But luckily for me, I do have my own little temperate microclimate - inside a backyard greenhouse. My 10' x 12' Northern Light Greenhouse sits about 30 feet from the house, between my vegetable garden and cut flower garden. Inside, there's a waist-high bench along the north wall, and instead of a floor, there's an in-ground bed along the south wall. The door is on the west side, and opposite that is an old wooden bread rack, that holds flats of seedlings when space gets tight in May.

In-ground beds are perfect for early crops of lettuce.

My greenhouse season begins in March (assuming that the soil in the in-ground bed has thawed out!) That's when I start transplanting the lettuce seedlings that I've started indoors. They go into the in-ground bed along the south wall. Along with those little transplants, I sow some spinach and a few other cold-hardy lettuce varieties. These are ready to eat by mid-April.

The in-ground bed bed works well for me. When I first got the greenhouse I had four whiskey barrels along the south wall, but found it difficult to keep up with watering. The in-ground beds are easier because they require far less water (the capillary action from surrounding soil is usually adequate), and as the weather begins to warm up, the ground stays cool so the greens don't get bitter as quickly. I've found it best to remove some of the old soil from the bed each year and fork in compost and some soilless potting mix. This improves aeration and reduces problems with fertilizer build-up.

The greens will tolerate temperatures of 20 to 30 degrees F, so I don't need to turn the electric heater on until early April, when I begin ferrying flats of seedlings from the house. All my seedlings get started indoors under lights. I find that in the greenhouse, the temperature and moisture extremes are too great for good germination. But, once the seedlings are up and growing, there's no better place for them than in the greenhouse. After several years of trial and error, I now start almost all of my seedlings about two weeks later than the recommended dates on the seed packets. The plants grow incredibly fast once they get out into the greenhouse.

With two shelves on the north wall and the bread rack on the east wall, I can squeeze in about 35 flats (gardeners like me need to have some kind of limit!). Watering is a twice-a-day ritual: before heading off to work and as soon as I get home. Because it's only 30 feet to the house, I just run a hose out there for watering. (Though in April, I have to lug watering cans because the hose is usually frozen solid in the morning.) Along with water, the plants need fertilizer to sustain rapid growth. I give them a weekly dose of Plant Health Care for Seedlings. The in-ground beds get a fresh layer of compost each spring and a couple handfuls of granular organic fertilizer. Since there's no rain to wash the fertilizer out of the soil, I find it builds up if I apply it any more often.

For heat, I use a 110-volt, 1,500-watt Titan Electric Heater. It's on a thermostat that's set to turn on when the temperature falls below 40 degrees F. (I keep it set at 40 to save money, but also because I find that cool evening temperatures keep the seedlings healthier.) Each morning, I also prop the door open for the day (unless it's still below freezing). This helps keep the greenhouse from getting too hot, and increases the flow of fresh air. My greenhouse has a vent in the roof and the two vents on the south wall with heat-activated openers. Since I'm rarely at home during the day, they are absolutely essential for preventing overheating.

Knock on wood, but in all these years, I have never had a pest problem in my greenhouse. Just as in the garden, I think the secret is to avoid stressing the plants. Be vigilant about watering, don't let the temperatures get too hot, fertilize weekly, and keep fresh air circulating.

By early May, I'm transplanting seedlings into the garden. It usually takes the entire month to get the greenhouse emptied out. The greens in the in-ground bed will eventually start to bolt, so I take them out and plant a half dozen eggplants, a couple pepper plants and a cherry tomato plant. Eggplants always struggle to survive in my zone 4 garden. The plants are usually so stressed from the cool weather that they are covered with bugs and yield no more than one or two misshapen fruits per plant. The first year I grew eggplants in the greenhouse, I got a bounty of fruit that looked like eggplants are supposed to look. My "hothouse" eggplants need minimal attention during the summer (I might water once a week), and with so much light and warmth, they produce early and keep going right into the fall.

In early September, I clear out enough space in the in-ground bed for some greens. The seeds get sown right in the ground, and I usually have lettuce by early October. I don't heat the greenhouse in the fall, so the eggplant and tomatoes are usually history by early October, but the greens grow happily until well into November. This past year I covered the bed with a layer of GardenQuilt when outside temperatures fell into the teens, and was still picking lettuce in December.

A freestanding greenhouse works great for me. It's the ideal environment for seedstarting and season extending. Of course, if I had a greenhouse attached to the house, I'd be able to grow orchids, gardenias, citrus and other tender exotics. But that's a whole other adventure!

If you have any tips and techniques to share, we'd love to hear from you. Write to us at: innovativegardener@gardeners.com