With a hoophouse, vegetables and greens can be grown all year long. All that is needed for a hoophouse 4 feet wide and 5 feet long are a dozen 16-inch cinderblocks, five 10-foot lengths of 1/2-inch CPVC plastic water pipe, a large sheet of plastic and two 10-foot two-by-fours.
The cinderblocks line the perimeter of the area that is to be enclosed. For better insulation, they should be set in a trench with the tops level to the ground with the hole sides facing up and down. Pour a footing, if wanted, for a firm foundation, but the blocks can just be set on the ground. Keep them even along both sides so that the plastic pipes can be inserted into corresponding holes.
Begin by placing pipes at each end, then leave about 16 inches of space between all four pieces of pipe. The pipes create an upside-down U-shaped framework, resembling a Quonset hut. To stabilize the structure, place rocks or dirt into the holes that contain the pipes and tie the last length of pipe to the underside of each upside-down U so it extends from one end of the framework to the other. The pipe can also be used for a sprinkling system, but do not cut the U-shaped pipes because they will lose their shape.
When the large sheet of plastic is draped over your framework, take into account the height of your hoophouse when calculating the length. Remember that too long is better than too short. Likewise, leave extra on the sides. Roll the plastic on all four sides around a length of two-by-four, several times to secure it. For extra weight and insulation, place clear plastic bags of leaves on the boards. When spring comes, use the leaves for mulch or in your compost.
Buckets of rainwater inside the hoophouse help prevent frost damage when the temperature drops into the single digits at night. Sprinkling the leaves of the plants with water before the sun warms the inside of the hoophouse also helps. If rain barrels are kept on the south side of the house in the sun, water can be accessed all winter long. Even on the coldest days, water generally flows by midmorning.
Hoophouses also hold moisture as well as heat. Water collects on the inside of the plastic when the temperature rises in the hoophouse, and then it falls like rain when the inside temperature cools.
If snow collects on the hoophouse, brush it off. Plants need sunlight. If the hoophouse gets too warm inside, just open one end. Be careful on windy days. The early spring winds can also separate the seams of the plastic along the top. If the air is still cold, tape them, but at the first sign of moths, discard them and replace them with cheesecloth. Tie a rope around the framework about halfway up and use clothespins to secure the bottom half of the plastic and the cheesecloth to the rope. This combination protects your plants from the wind, keeps the soil from drying out, and prevents moths and grasshoppers from getting inside.
A hard summer rain can make small gaps here and there in the loose weave of the cheesecloth, big enough for grasshoppers to crawl through, so either remove it before the rain or afterward drape another layer over the first. At 50 to 69 cents a yard at the local fabric store, it seems easier to just add on. Grasshoppers do not like humidity. If they get caught inside your hoophouse, they cling to the cheesecloth in the early mornings. Just catch them in your hands, remove them to the outside, and let them fly away to feast on the native plants that, hopefully, grow abundantly in the rest of your yard.
Gardening all year long with a hoophouse is rewarding and fun. The quality and taste of veggies and greens freshly harvested from the garden is beyond compare. With two hoophouses, plants can be grown that flourish in the heat, such as tomatoes and peppers, in one and cool weather veggies, such as kale and broccoli, in the other.
Rebecca Snow is a Master Gardener volunteer. Dana Prom Smith, a Master Gardener volunteer, is coordinating editor for the Master Gardener Column. He can be contacted at firstname.lastname@example.org. For more information about the Master Gardener Program, call program coordinator Hattie Braun at 774-1868, Ext. 17, or visit http://highelevationgardening.arizona.edu">highelevationgardening.arizona.edu.)