Ready for a greenhouse? - gardening - Brief Article

Sunset, Jan, 2000 by JIM McCAUSLAND

Knowing your options can help you decide

For avid gardeners a greenhouse is an essential outdoor room for plants. It's a cozy year-round home for orchids or other exotics, a winter shelter for tender perennials like geraniums, and a nursery for starting seeds weeks before the last spring frost.

If you're in the market for a greenhouse, consider these factors.

Space, style, costs

"Greenhouse space is like money; you never seem to have enough," one owner told us. As greenhouse size increases, the cost per square foot decreases. Unless you plan to use a greenhouse only for seed-starting and potting, get one that's at least 6 feet wide and 8 feet long. If finances dictate a smaller unit, buy a model that can be extended later.

Rectangular freestanding greenhouses are very stable and designed to stand up under a fair snow load (ask the manufacturer for details). Many good units are in the $2,000 to $3,000 range, with top-of-the-line models running $7,000 to $8,000.

Lean-to models fit well in tight spaces, such as on a patio facing an exterior wall. They tend not to do as well under heavy snow loads (again, ask before you buy). Prices start at about $900 for a unit with double-walled polyethylene glazing, $1,200 for polycarbonate, and $1,300 for glass.

collapsible greenhouses ($270 to $370) are good where space is a problem.

Framing

Most greenhouses have frames of wood or aluminum. Wood will lose no significant heat through the frame. Over time the wood fades unless you keep it painted or finished, and it may rot or warp.

Aluminum frames retain shape well, won't corrode, and are often color-coated. Some heat is lost through the aluminum (some units minimize heat loss with neoprene gaskets that separate the metal from the glazing).

One manufacturer uses rigid steel-core PVC pipe for framing and shelving.

Glazing

Although traditional glass greenhouses have single panes, double- or triple-walled panels trap more air and thus have greater insulation value--a crucial consideration in cold-winter climates.

Glass. Fireproof, but breaks more easily than other options.

Fiberglass. Diffuses light well; good shatter resistance, a plus where hailstorms are common. Flammable.

Polycarbonate plastics. Transparent, almost unbreakable. Flame-resistant. Usually double-walled.

Acrylics. Like polycarbonates, but less resistant to breakage or fire. Clarity and rigidity approach those of glass, with better shatter resistance.

Double-walled polyethylene. Milky white, flexible. Diffuses light well and resists ultraviolet light. Flammable.

Accessories

Some greenhouse sellers offer just the shells, others fully equipped units. When you compare prices, your bottom line should include at least the following accessories: benches or shelves for plants ($10 to $25 per linear foot); a small fan for air circulation ($25); automatic solar-powered vent openers ($40 to $100); a heater ($50 to $100 for electric, considerably more for gas) in any area where it freezes; a minimum-maximum thermometer (about $20); and shadecloth ($50 to $130) to filter summer sun and reduce heat buildup.

Make sure electrical wiring and heating systems meet safety codes, and follow the manufacturer's instructions for heater placement and setup.

Site

Ask your city or county building department if you need a permit to erect a greenhouse. Select a site that's near water and electric outlets and gets at least six hours of sun per day. Unless you set the greenhouse on an existing paved surface or deck, you'll need to level the ground and install a foundation for the frame. Pressure-treated 4-by-4s or 4-by-6s provide sufficient support for most greenhouses. Finally, install a floor of loose-laid bricks, pavers, or pea gravel.

Manufacturers

Many of these firms sell direct; others refer you to dealers.

Aluminum-frame models

* B.C. Greenhouse Builders; (888) 391-4433 or www.bcgreenhouses.com.

* Garden Grower's Greenhouse; (888) 929-8383 or www.gardengrower.com.

* Sunglo Greenhouses; (800) 647-0606 or www.sunglogreenhouses.com.

Redwood-frame models

* Santa Barbara Greenhouses; (800) 544-5276 or www.sbgreenhouse.com.

* Sturdi-built; (800) 334-4115 or www.sturdi-built.com.

* Sunshine Gardenhouse; (888) 272-9333 or wwwgardenhouse.com.

Steel-core PVC-frame models

* Farm Wholesale; (800) 825-1925 or www.farmwholesale.com.

Retail dealers

* Charley's Greenhouse Supply sells temporary and permanent aluminum-frame models and supplies; (800) 322-4707 or www.charleysgreenhouse.com.

* Rain or Shine sells aluminum- and redwood-frame models and supplies; (800) 248-1981.

* Smith & Hawken sells freestanding aluminum-frame models; (800) 776-3336 or www.smithandhawken.com.

* Yard Works sells aluminum- and redwood-frame models, collapsible units, and supplies; (800) 369-8333 or www.yardworks-greenhouses.com.

Foldout greenhouse

Designed by a company that makes ice-fishing shelters, the collapsible Germinette sells for $270. Measuring 4 feet wide, 6 feet long, and just over 6 feet high, it's covered with sturdy woven polyethylene sheeting. When not in use, the unit folds up.