To build or not to build, that is the question.
Each year, dozens of gardeners attend the solar greenhouse class I have taught for about the quarter century. Most come thinking about and almost tasting the fresh, ripe tomatoes they will haul out by the boxful.
I do not mean to burst anyone's bubble, but greenhouses are expensive and a lot of work to build, and they take time to operate. Add to that the considerable expense for heating and cooling as well as the cost of seeds, soil and other things, and it is easy to see that greenhouses are not for everyone.
I usually have one or more people in class who have owned a milk cow who help illustrate the point. While a greenhouse might not be as demanding as the cow and it certainly does not moo when it needs attention, it has its own set of demands that must be satisfied.
As with any project, I find it helpful to list the pros and cons of getting involved and then considering the options. Decide what you want to grow, when you want to grow it, and who will take care of the plants. Then proceed to ask yourself the relevant questions.
Costs of building a hobby greenhouse can vary from several hundred to many thousands of dollars. Operating cost can be significant in our area if you plan to use the greenhouse in the winter when the plants need heat or in the summer when they need cooler temperatures.
Decide whether you want to build your greenhouse or have a contractor do it. Also, decide whether you want to design your own or whether to purchase a greenhouse kit. Each has pros and cons, but choose a design that will be successful for you.
Ask yourself if you want an attached or detached greenhouse. Attached greenhouses can collect and share heat with your home and are easy to access. They also may breed pests, increase humidity and odors and create a strain on the home-heating system.
One of the most difficult decisions is the structure's style. Look at the choices in catalogs and then visit as many types of greenhouses as possible. Whatever you buy, it is going to be a long-term investment that will hopefully provide the best growing area and blend well with your home and landscape design.
There are many design styles. Each has different strengths and weaknesses. Consider the glazing material or covering for your greenhouse. Styles like the dome, gothic arch, Quonset, curved-side lean-to and tri-penta are more suited to flexible coverings like polyethylene.
If you plan to use rigid coverings such as glass or plastic, consider the A-frame, gable roof, slant-side and straight- or slant-side lean-to styles. The gable roof and Quonset are more efficient to heat and cool, while dome and tri-penta styles are attractive but are more difficult to construct and heat and cool.
An A-frame is easy and inexpensive to build, but the usable growing area is small and awkward. If the greenhouse is attached or near your home, make certain it fits well with your home both in terms of style and materials used.
After you choose your style, select the location. All greenhouses need sunlight, and if they do not get light, plants will not grow. Maximum sunlight is critical to grow transplants or to try to produce vegetables during the winter.
These are the preferred greenhouse exposures, in order: 1. south or southeast; 2. east; 3. southwest; 4. west; 5. north. A western exposure is often too hot in summer and a northern exposure does not get enough light for most plants.
Other factors to consider are adequate soil drainage, easy access to the greenhouse and to get soil and other materials into the structure. Your location needs ready access to water, heating fuel and electricity. Make sure the site is level, and avoid low areas where cold, humid or foggy air can stagnate. These areas are more expensive to heat and may not get sufficient light.
Choosing the greenhouse size is also critical. A small greenhouse often costs more to operate, and if it is too small, it might not need your needs. Temperatures inside a small greenhouse can fluctuate wildly, and it may cost as much to heat as a larger greenhouse.
Small houses may have limited headroom and are hard to work in. Consider 100 square feet as a minimum size, but 200 square feet is better. While there are no magic numbers, choose a size slightly larger than you think you need, because plants always grow.
If the greenhouse bug infects you, you might be adding on or building a second house in the future.
Larry Sagers is the horticulture specialist, Utah State University Extension, Thanksgiving Point.