Hobby greenhouse helps gardeners stay busy year-round
The weather is clearly changing as nighttime low temperatures dip to the 40s and the tree leaves start to change colors and get ready for their autumn dance to earth. You can smell the cooler fall weather, and meteorologists are talking about wind chill temperatures again. The first frost and then the first freeze normally arrive in the next two or three weeks on the calendar.It’s time to start planning for any tropical or annual plants you want to save and bring inside for winter. Some plants may be too large to save, but you can take stem cuttings to root and carry over for spring. Most tropicals need to be kept near windows in good light if you are going to try to winter them in the house.
Many people look at the killing fall freeze as the end of a special season or memory and a chance for a clean palette to start their garden anew next spring. Others can’t bear to lose beloved plants, large porch or patio gardens, or special plant collections.
You can save a few plants in your house, but space and access to light often limit the number of plants you can bring in the house. This makes a hobby greenhouse the best option.
A hobby greenhouse can also be a fun way to produce vegetables through the winter, to grow seeds and cuttings, to start transplants for next spring or to start a collection of orchids, begonias, bonsai or the special plants of your choice.
You can buy a kit greenhouse at local stores or via the Internet, or you can build a greenhouse frame and cover it with a number of greenhouse skins or glazings. Decent kit greenhouses start at about $1,000 and go as high as $20,000. Most of the inexpensive kits are made of lightweight galvanized metal or polycarbonate extrusions and are covered with plastic film or single-wall polycarbonate panels. The frames go up in cost as the metal frame gets heavier or you switch to aluminum frames or painted frames. A few kits use redwood or cedar wood as the frame, but more than 85 percent of the kits sold use metal frames, which probably offer the most strength for the money.
The earliest types of greenhouses that used more glazed glass are still available but not used as often because of the glazing cost and because it takes more structure to support the glass. Glass is available in 1/8-inch-thick tempered glass and in energy-saving insulated glass panels. The most popular glazings these days are single-wall corrugated clear polycarbonate panels or the energy-saving twin-wall polycarbonate in 6- or 8-millimeter-thick panels.
Some kits still use corrugated fiberglass, and newer kits use the more expensive corrugated or twin-wall acrylic panels that will stay clear longer. Greenhouse-grade ultraviolet-resistant polycarbonate panels offer the most strength, durability and light transmission for the money.
Twin-wall panels save almost 30 percent to 35 percent in energy. Greenhouse copolymer plastic film is the least expensive glazing. When you install two layers and blow air between the layers, greenhouse plastic film is one of the most energy-efficient choices.
If you build your own wood or metal frame or convert a garage, shop or other building, you can buy good greenhouse glazing to put on your frame. You can use 4-foot-wide corrugated polycarbonate panels that install by overlapping the panels and screwing them to the frame.
You will need heat in your greenhouse. A unit heater is usually the best choice. Natural gas is generally the cheapest commercial fuel, followed by propane. Electric heat is the cheapest to install but costs the most to operate.
Even if you only use the greenhouse in fall, winter and spring, you will need ventilation, as all greenhouse owners very quickly appreciate the power of solar energy. You can provide winter cooling with side and roof vents or with a motorized shutter on one end and an exhaust fan on the opposite end.
It is usually best to automate the ventilation on a thermostat, because we often need cooling near the middle of the day even in the winter. It is not unusual to have the fan come on to ventilate on a 40-degree or 45-degree day. If it is clear and sunny outside, it is possible for the greenhouse temperature to rise to more than 100 degrees because of solar radiation if you are not ventilating.
You will probably need to add shade cloth and an evaporative cooler if you want to use the greenhouse in summer.
Although you can buy hobby greenhouses from mail-order catalogs or over the Internet, I would encourage you to buy this specialized equipment locally for the best advice on frames, glazing materials, sizing, heating and cooling equipment and shade percentages for this area. There are several good suppliers in Oklahoma City and Tulsa that would be familiar with our area’s conditions to help you select the right hobby greenhouse for your application and crops.
Now is the time to plant pansies, viola, ornamental kale and cabbage and to select and plant spring flowering bulbs such as tulips, crocus and daffodils. This is also a great time to mulch your more tender hardy plants to help insulate their roots and protect them for the winter ahead.
Rodd Moesel serves on the Oklahoma Horticulture Industrial Council and the Oklahoma State University agriculture dean’s advisory committee. He is a former president of the Oklahoma Greenhouse Growers Association. E-mail garden and landscape questions to email@example.com.