A greenhouse doesn’t have to be an expensive permanent structure, designed for one year of use. If you only need a greenhouse in certain seasons, or if the cost of a permanent greenhouse puts you off, then a temporary or portable greenhouse can come in handy. Tunnel or hoop houses are a type of temporary greenhouse that hobby growers often use.
These seasonal greenhouses consist of a transparent plastic cover stretched over a PVC, aluminum, wood or steel frame. They can be installed in a few hours and do not require a foundation. There are plastic films available for the cover that will serve for at least 5 years. It is easy to make a tunnel greenhouse to fit a single raised bed or to cover a specific area.
The disadvantages of a hoop house are poor insulation and ventilation. It is possible to add a second layer of plastic and pump air between the two to add some insulation. Ventilation is achieved by rolling up the sides in hot weather or by leaving the ends open. However, in spring and autumn, when the sun warms the air inside, these greenhouses work quite efficiently.
Many hobby growers use a greenhouse to extend the growing season. It serves as an intermediate stage in the preparation of plants for the garden. By starting the seeds indoors and transferring the plants to a greenhouse, the plants have a head start. They grow more compactly and with greater energy in the spring greenhouse with sunny days and cool nights than indoors.
As summer arrives, the sides of the greenhouse cover can be rolled up for ventilation and heat control, or even removed completely. In the fall, the cover can be replaced and tender plants placed inside to protect them on cool nights.
Heat-loving vegetables such as tomatoes, cucumbers, peppers and melons can be planted directly in a raised bed and a hoop or tunnel greenhouse above it. The cover can be raised in hot weather so air can circulate and plants can take advantage of the rain. Then, as fall arrives and the weather cools, the cover can be replaced so crops continue to grow and mature well into the season.
Seasonal or temporary greenhouses can also be used to protect borderline hardy plants in the winter. The temperature under the plastic cover is usually a few degrees warmer than the outside air, and the cover also reduces the drying and cooling effect of the wind. As the plants inside the seasonal greenhouse go dormant, they can be covered with straw to further protect them from the cold outside.