Gardening: Greenhouses growing in popularity

Universal UclickMarch 7, 2014 

The gardening season never ends when you have a greenhouse: There’s always something growing on.

Greenhouses give warm-climate gardeners a chance to experiment with truly tropical plants year-round. In any climate, a greenhouse is the perfect place to get ahead of the calendar and start seeds and tend to transplants. Not surprisingly, gardeners thrive in a greenhouse environment, too.

“A lot of people just want to sit among their plants and do nothing, just enjoy it,” said Shelley Newman, vice president of Hartley Botanic, which has been making greenhouses in England since 1938.

Plant collectors used to be the main customers for greenhouses, said Charley Yaw, owner of Charley’s Greenhouse & Garden in Mount Vernon, Wash. Orchids, tender cacti and fancy flowers filled the shelves in these elaborate structures. Now, a large new generation of gardeners interested in starting seeds early and vegetable gardening in the offseason is making room in its backyards for hard-working greenhouses.

“There are a ton more greenhouses being sold today than 20 years ago,” Yaw said. “And it doesn’t take a real expensive or sophisticated greenhouse to grow vegetables.”

Greenhouses can be just about any size, but the experts generally recommend a greenhouse with a footprint of about 8 feet by 10 feet. Yaw’s formula for customers is easy: “Figure out what you want, then add 50 percent,” he said.

If two people will be working in the greenhouse together, a 10-by-12-foot space allows more elbow room, Yaw said, and more growing space, too. Hartley Botanic’s most popular greenhouse size is 11 feet by 20 feet.

Building restrictions and setback limits may influence your decision, so it’s a good idea to check on local zoning and homeowner association regulations before you get started. Temporary structures may not be regulated.

Putting up a permanent greenhouse requires a bit of planning. You’ll have to consider the layout of your property and the relationship of the greenhouse to the rest of the garden and your home. It should be on the south side of your house to take best advantage of the light, and away from screening evergreen trees.

A path through the middle should be paved solidly to avoid muddy feet; gravel or pavers under the growing benches also help keep the greenhouse tidy. It’s practical to have a patio or pad of pavers, bricks or stone outside the greenhouse door; this area can also be used as a staging area for plants making the transition from the greenhouse to the garden.

Hartley Botanic’s greenhouses have glass panels, but not all greenhouses use glass. Plastic polycarbonate panels are popular, Yaw said, and the material is especially good insulation. Polycarbonate also diffuses the light, so plants do not get burned in bright sun.

Depending on where you live, an electric or gas heating system may be necessary, although passive heat will suffice on many days. Fans and automatic vents help prevent overheating.

Donna Clark, a retired garden designer in Greensboro, had a modest, hardworking greenhouse on the back of her two-car garage when she lived in Connecticut. When she and her husband moved south, her dream of a Hartley Botanic greenhouse came true. Her Victorian-style greenhouse is 11 feet by 10 feet, with a gravel floor. Shelves for plants line the sides, and a potting bench fits neatly against the back wall.

“Some people want a fancy car,” she said. “I wanted a fancy greenhouse.”

Clark grows annual flowers from seed in her greenhouse, nurturing the tiny plants before transplanting them into the garden; she also starts seeds for her extensive vegetable garden. Last year, she grew cucumbers in the greenhouse and harvested them long before cucumbers could have been produced outdoors. This winter, she is using her greenhouse as a studio, experimenting with mosaics.

Greenhouses are not an impulse purchase. Inexpensive do-it-yourself models start about $500 and run up to about $2,000. Larger greenhouses with more features are substantial structures and cost $5,000 or more. Hartley Botanic’s fancy Victorian greenhouse is quite an investment, at $45,000 to $50,000.

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