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Diggin' Florida Dirt: Winter's coming, do you need a greenhouse?

 
Instead of jamming the inhabitants together for the winter, Rhoda Smith gives everyone room for good air circulation in her new greenhouse, and she makes it aesthetically pleasing — she spends a lot of time in there.
Instead of jamming the inhabitants together for the winter, Rhoda Smith gives everyone room for good air circulation in her new greenhouse, and she makes it aesthetically pleasing — she spends a lot of time in there.
Published Oct. 17, 2014

To the folks up North looking down their runny red noses at us in winter, Florida gardeners who worry about a few frosty nights have obviously been out in the sun too long.

"When I mention I have a greenhouse and live in Florida, invariably, I will get asked by several people: WHY do you have a greenhouse when you live in FLORIDA?" a zone 9 gardener confided on a GardenWeb online forum.

Forget it, a Washington gardener on the forum told a Sunshine Stater seeking tips for building a greenhouse. You need a shade­house!

As we approach winter — which will be colder than usual in Tampa Bay if you believe The Old Farmer's Almanac — I wondered: Is building a greenhouse in Florida like buying a backyard freezer in Alaska?

The answer depends on whom you ask, where you live, what plants you grow and, most important, how attached you are to them.

"My greenhouse helps me sleep at night," says Rhoda Smith of South Tampa, who expanded and upgraded hers last year.

"I have a lot of plants that are rare — some that aren't available anymore. They're my babies!"

This is a woman who fractured her knee a few years ago while racing sunset to move plants ahead of a cold snap. She has about a thousand varieties of bromeliads and lots of heat-­loving tropicals like calatheas and anthuriums.

Her first greenhouse, built 12 years ago, gave her so much peace, she invested $30,000 to expand and upgrade it a year ago.

Merle Deland of Lakeland has a greenhouse, too, but he doesn't recommend it for most of us. The retired owner of the former Cooper's Flowers & Greenhouse in Orlando, Merle maintained huge commercial greenhouses filled with poinsettias, Easter lilies and mums for decades.

Today, he's indulging his begonia fetish with an 1,800-square-foot greenhouse, twice the size of his home.

It keeps exotic rex varieties warm on cool nights, and its cooling pads and fans keep finicky plants comfy on warm nights.

"But most Florida gardeners are better off with shadehouses," he says, explaining that greenhouses can become incubators for plant fungi and bacteria. "The problem is ventilation."

• • •

Whether you settle on a greenhouse or a shadehouse, Rhoda and Merle offer some tips:

From Rhoda:

If you opt for a greenhouse, shatter-proof glass roof is much better than plastic.

"I can see the trees!" says Rhoda, whose old greenhouse was covered in thick plastic.

A steeply pitched roof helps prevent leaves from piling up, and having windows that can open aids ventilation. Rhoda has an exhaust fan over the front door, three other fans strategically placed, and two heaters.

Some people suggested she install a sprinkler system. She didn't.

"Some of my plants need less water than others. It's better if I just go in there with a hose and buckets of water from my rain barrel," she says.

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From Merle:

A shadehouse can be as simple as a wire frame overlaid with shadecloth, or as the old-timers used to do it, a little house constructed of inexpensive wooden plaster laths spaced an inch or so apart for air circulation.

"Cover it with screen cloth. When it's warm, roll up the cloth on the sides so the air circulates," he says. "And when it gets cold, just put a sheet of polyethylene over it and they're protected!"

Hoop-style shadehouse kits are available online.

If you decide you want a greenhouse, orient it so the center line runs north to south, if possible, so the plants will get east-west sun. Locating it in some shade will help prevent scorched leaves on sunny winter days.

Make sure you have an exhaust fan to release hot air. Another fan in the peak will pull up the cooler air near the ground on warm days. Sides that hinge out or open can also help keep the temperature down and provide ventilation.

For a builder, Merle recommends Imperial Builders & Supply in Apopka (imperialbuilders.com).

Both Rhoda and Merle warn, if you opt for a greenhouse, be sure to plan for room to get around inside, so you can tend to your little refugees. Don't rescue your plants from the cold only to let them die of neglect crammed in a stuffed greenhouse.

Imagine what the gardeners up North would have to say about that!