Greenhouses allow gardeners to pursue hobby year-round

Some of us are saddened by the onset of winter. They include avid gardeners — dedicated plant people who hate to see that first freeze take down their prized babies from the summer.

Most of us in that camp eventually find that a home hobby greenhouse makes life wonderful again. Plants that otherwise might have been lost can be carried over from one year to the next. New plants can be started, and off-season vegetables can be grown and harvested just before mealtime. Greenhouses require planning, however. Let’s look at some guidelines.

Find a suitable site. A place with morning sun and shade during the afternoon would be ideal. It should be reasonably convenient to your home, and you’ll want utilities nearby. Check building codes to be sure it’s all legal. Consider its appearance as you determine whether it will be in a visible part of your landscape, or perhaps tucked away behind screening shrubs. If you’re going to use evaporative cooling during the summer, orient your greenhouse north-and-south. Put the evaporative pads on the south end and the exhaust fan on the north end, so that you can take advantage of the prevailing southerly breezes.

Determine its size. Get a greenhouse as big as your space and budget allow. Very small structures have far less volume of air, so they can overheat quickly. It’s usually best to start with at least a 10-by-20-foot house. If it can be larger, so much the better.

Choose a covering. This is where the appearance of the greenhouse enters the picture. Glass greenhouses are, by far, the most attractive in landscape settings. Plastic houses cost a lot less, but they’re also not nearly as attractive, so they normally end up in the utility areas of our landscapes.

Bench options. Greenhouse tables are normally called "benches" and need to be made from a decay-resistant material such as aluminum, redwood or cypress. Build them carefully, because they’ll end up carrying a great deal of weight. They should be at a convenient height so that you can easily reach your plants. They should be sized so that you can comfortably reach every plant on them. For a bench that you’ll be accessing from one side, that’s probably 36 inches, or 48 inches if you have aisles on both sides of the bench. The aisles themselves need to be wide enough only to allow you to move about. You pay for the heating and cooling of aisle space just like you do for the plants on the benches, so keep corridors to a minimum.

Heat sources. You’ll want to heat your home greenhouse. However, plants get along better at cooler temperatures than people do. It depends on the types of plants that you’re growing, but aim at somewhere between 55 and 65 degrees. Electric heaters can work for small structures, but they’re vulnerable to power outages, so you’ll need some source of emergency heat. Small gas space heaters can also work, but many require vents. Some have blower fans to aid in dispersion of the heat, and they also will be at risk during power outages.

Shade fabrics. You can either shade a greenhouse from the outside, or you can suspend a shade material inside. External shades are better, because they stop the sunlight before it actually enters the greenhouse. Special nursery shade fabrics are available, even in custom sizes. They come in many different percentages of shading, but many of us have found that 60-65 percent shade is ideal. If you’re having a covering custom-made for you, have grommets installed to facilitate tie-downs. Retail nurserymen in your area may be willing to order one, or they can be purchased online.

The add-ons. Consider a long iron pipe hung above your benches to allow for hanging baskets in otherwise unused space. Have an accurate thermometer in your greenhouse. You also may want a temperature alarm that rings into the house when the heating fails. You’ll certainly want a light, and a faucet is pretty much a given. The faucet should be mounted on an iron pipe. That will eliminate the chance of breaking the pipe as you pull on the hose. You’ll want some type of fertilizer injector to aid in feeding each time that you water, or you can use timed-release fertilizer pellets.

Neil Sperry publishes Gardens magazine and hosts Texas Gardening radio show from 8-11 a.m. Saturdays and Sundays on KRLD/1080 AM. Reach him during those hours at 214-787-1080.

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