At some point, most gardeners want a greenhouse. They may want to extend a short season or defy winter by growing year-round. They might want to start unique varieties from seed or grow tropical plants in the high humidity. Protected growing is more reliable than a traditional garden. That’s something to think about as our climate gets more unpredictable.
A greenhouse is a big investment, so take some time to plan.
- First decide the purpose of the greenhouse. Several scenarios are mentioned above. Do you want it to be freestanding or attached to the home? Will it double as a heat source?
- Know your budget. What can you afford to spend on the greenhouse and its construction? This will overlap with siting the structure. I recommend building the largest you can afford, because as soon as it’s up and running, you’ll want more room. Trust me!
- Will you build it yourself, or hire a contractor? Infrastructure includes electricity, water, heating, cooling, and perhaps a foundation. Flooring can be dirt, gravel, or concrete. Each decision dictates price. Crunch numbers first.
Siting the Greenhouse
- Your greenhouse needs to be in full sun. Late afternoon shade is ok and actually welcome in summer, but you want to build your greenhouse in a sunny spot. For maximum light, especially in winter, orient it east to west, and avoid trees on the south side.
- Do you have enough room? You want the greenhouse to be wide enough for a 3’ pathway down the center to accommodate a wheelbarrow, and 2.5’ wide benches or growing beds along the sides. That’s the bare minimum width.
- How much headroom do you need? Do you want to hang pots or put up high shelving?
- Length depends on space. Do you want a 100’ structure? Do you have that kind of room? Check with your town or county on setback requirements, zoning, and permits. Those things will also dictate size and placement.
- Does the location offer easy access on foot or in a vehicle? Will it be easy to bring in power, heat, and water?
What type of greenhouse do you want? Again, this will depend on your budget, but you must also consider your climate – snow load, wind, rain, heat, and hail. Check with your County Extension Office for the best designs for your climate.
An attached greenhouse can be a lean-to style that comes in a kit, or an addition that blends in with your home’s architecture. Depending on what you are growing, you may or may not need supplemental heat, but you will need water, drainage, electricity, shade, and a cooling system. Consider adding thermal mass for radiant heating and cooling. Be sure an attached greenhouse receives enough light for proper plant growth.
A freestanding greenhouse can be as simple as an unheated DIY hoop house of PVC piping and rebar. Skip the expensive infrastructure by using a hose for watering and an extension cord for a fan or heater. You may want to go all out with a professional grade greenhouse with all the options. There are dozens of choices in between the two extremes.
Roofs can be pitched, round, or a gothic arch. Frames are of wood, metal, or PVC, and siding can be glass, polycarbonate, or polyethylene film. If the choices are overwhelming, buy a kit.
Geodesic dome greenhouses offer year-round growing without needing heat in winter. The dome shape withstands snow and wind. It is passive solar with a pond for thermal mass for heating and cooling.
Read the FAQ on the Hobby Greenhouse Association website. Visit nurseries, schools, and the County Extension to see greenhouses in use. Call greenhouse suppliers and ask questions. Then get growing!