Gardening Articles: Health :: Houseplants

The National Gardening Greenhouse

by Charlie Nardozzi


One of my favorite projects is planting the greenhouse tomatoes, in November.

It's hard to imagine anything green in Vermont in winter. The dominant colors surrounding National Gardening's office building here in Burlington are blue sky, white snow, and black pavement. But creative thinking is exactly what greenhouse gardening takes, and one winter our collective imagination went wild when we attached a greenhouse onto the front of the building. Visions of ripe tomatoes, tropical fruit, and lush year round foliage danced in staffers' heads. Before I knew it, I was ordering plants, mixing soil, and planting seeds -- while the snow fell outside. As soon as the greenhouse was finished, I had seedlings ready to transplant.


National Gardening's attached greenhouse is also the main entrance.

Blowing Hot and Cold
Our south-facing, 12- by 18-foot greenhouse, surrounded on three sides by a paved parking lot, doubles as the main entrance. The ceiling slopes from nine feet, at the end attached to the building, to six feet before dropping down to the three-foot kneewall. The back is open to the reception area and the entire building. It features two automatic ceiling vents, six windows, and double-pane, insulated (R 3.25), tinted glass. The glass tinting reflects heat producing, infrared rays away from the greenhouse, while allowing growth-inducing, ultraviolet rays to penetrate. The ceramic-tiled floor slopes to a corner dry well for water drainage.

One thing you can rely on in Vermont is the cold. To keep the greenhouse warm for human and plant life, we installed base-board heaters. With the help of soil mass, plant matter, and base-board heat, the soil temperature never drops below 60&deg F and the air temperature never drops below 56° F.

Keeping the greenhouse cool in summer is another matter. Even with all vents and windows open and portable floor fans blowing at high speed, temperatures inside the greenhouse still averaged 86° F during the first summer, and many days were uncomfortably well into the 90s. That's great for growing bananas, but quickly causes anyone working nearby to wilt. Sunshades and an exhaust fan installed prior to the following summer reduced the heat.

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