Grow plants year-round with a greenhouse

Entering the warm, humid, blossom-filled oasis of a greenhouse on a snowy winter day seems magical. And an increasing number of people are bringing that experience home with their own greenhouses.

Dorian Winslow, owner of Womanswork, a gardening company specializing in gloves and sun hats for women, is building a greenhouse at her home north of New York City because, she says, "I want to be able to pluck a lemon or lime from my own citrus tree in the dead of winter." She also plans to grow lettuce year-round, and start new plants from seed for her container and vegetable gardens.

It's all in keeping with a movement in gardening toward growing your own food.

But as enticing as it may sound to snip lettuce leaves and pluck lemons year-round from your greenhouse, there are many decisions to make before building one:

Kits vs. custom designed

Whether you build a greenhouse from scratch or buy a kit depends on your level of do-it-yourself expertise, as well as how much time and money you want to invest.

For people interested in custom designing and building a greenhouse, the US Department of Agriculture has developed a software program called "Virtual Grower," which the public can download for free.

Another source is the book "How to Build Your Own Greenhouse" (Storey Publishing, 2009) by Roger Marshall, who designed and built two 300-square-foot greenhouses for under $500 each by using recycled materials.

If you decide on a kit, on the other hand, buy from a reputable manufacturer, as kits vary in quality.

Charley Yaw, owner of Charley's Greenhouse in Mt. Vernon, Wash., has, with his wife, Carol, been helping gardeners select, build, and equip greenhouses since 1975. Most of Yaw's models come with a detailed manual and assembly video, and he has staff available to answer questions.

Another option is to buy a ready-made greenhouse, but if you go that route, be aware that these greenhouses arrive on a trailer and weigh from 500 to 1,000 pounds.

For more on whether to build or buy, consult "Greenhouses and Garden Sheds" (Creative Publishing International).

What size and type do you need?

A greenhouse's size is often dictated by budget and time constraints. Ask yourself how much time you are realistically able to devote to greenhouse gardening.

"If you are an inexperienced gardener, get a moderately sized greenhouse until you know what you are doing," Mr. Marshall suggests. "If you are experienced, get the largest you can afford; you will fill it!"

Mr. Yaw maintains that 8 feet by 10 feet is about as small as you can go and still enjoy the greenhouse. "People tend to underestimate the size they should have," he says.

Attached greenhouses gain warmth from the house and are easily accessible, but freestanding ones may be sited anywhere on the property and have maximum exposure to the sun.

To heat or not to heat

How you heat your greenhouse will depend on the climate and what you want to grow. According to Marshall, many vegetables will survive almost to freezing. Orchids and tropical fruits and flowers require a warmer environment.

Ideally, he says, a greenhouse should receive eight to 10 hours of sunlight a day, including in the morning.

In colder climates, additional heat is usually required, with small portable electric heaters being most popular. However, if all you want to do is extend the growing season, an unheated greenhouse can add up to six weeks at each end of the season.

Yaw reports growing interest among young people in buying greenhouses because of the appeal of growing organic food for their families.

Some even extend the bounty to their communities. When their greenhouse is up and growing, Dorian Winslow and her husband, Tom, plan to donate part of their crop to their local food pantry.

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