In this hoop house FAQ, I’ve created a list of the top questions / answers that backyard gardeners ask about growing vegetables and herbs in a hoop house (a.k.a. high tunnel or poly tunnel).
If you have other questions not answered here, send me an email with the questions by using my contact form. I’ll add the questions / answers to this page.
Common hoop house questions
The purpose of a hoop house is to allow gardeners to start growing as much as six weeks sooner in the year and extend the season as much as six weeks when the weather turns cold.
A high tunnel is the same thing as a hoop house. It’s a season extending device that protects vegetable plants and herbs against the elements. Market growers tend to call hoop houses high tunnels, while backyard growers tend to call them hoop houses. Generally, a high tunnel is on the larger side, while a hoop house is smaller.
A poly tunnel is a device like a hoop house or high tunnel. It covers plants with plastic to protect them from the elements. Unlike a high tunnel, the plastic can be suspended by hoops high off the ground or only a few feet off the ground.
Protected culture is when gardeners or farmers use techniques to protect plants from the elements. Protected culture techniques include hoop houses, high tunnels, low tunnels, row covers, cold frames, poly tunnels and more. Like agriculture, aquaculture, permaculture, etc., it’s a way to grow plants.
A well-constructed 12′ long x 6′ wide x 7′ high hoop house kit for your backyard will cost about $390. This is a worthwhile expense because a hoop house or high tunnel will allow you extend the growing season and protect your vegetables from the elements.
A hoop house or high tunnel is a type of greenhouse. Typically, greenhouses are made from heavy glass or Plexiglas and are more permanent. Small hoop houses, on the other hand, are made from metal or plastic hoops with a lightweight plastic cover. They cost less. The big advantage of a backyard hoop house over a greenhouse is two people can move it pretty easily.
A backyard hoop house or high tunnel is a structure made from hoop frames with a plastic covering. The structure allows warming sunlight to pass through, but prevents some of the heat from escaping. This increases the temperature inside and warms the soil so that plants can still grow when it starts to get cold outside. A hoop house also protects plants from wind and damaging rain, making for a more hospitable environment for vegetables.
Where it’s cold in the winter, backyard gardeners use hoop houses to extend the growing season and otherwise protect vegetable plants from the elements. Common vegetables that really benefit from hoop house growing include tomatoes, early and late season salad greens, early season beets, cucumbers and more.
Polytunnels or hoop houses are a type of greenhouse. Both benefit from trapping the sun’s heat. Both also can sometimes benefit from added heat. On the one hand, greenhouses typically are made from materials that insulate better, so they sometimes will need less artifical heat than hoop houses. On the other hand, polytunnels are made from less expensive, lighter materials. Because of this, you can usually move them from one location to another much more easily.
I find that tomatoes, cucumbers, beets and salad greens of all types really benefit from hoop house growing. But you have to use different strategies for different plants. Tomatoes, for example, should be started from seed in containers in a warm environment. They won’t be able to tolerate cold nights in an unheated high tunnel. As soon as the second leaves start, you can move them into the high tunnel during the day when the temperature is warm enough. Then transplant them into the ground in the hoop house when the nights are warm enough.
There are a number of methods that people use to heat hoop houses when it’s cold outside. Each has varying degrees of success. Some attach a shed to a hoop house and put a properly installed wood stove in the shed. The wood stove heats the air in the growing area. Some use the heat from decomposing compost. Some heat hot water and run warming tubes under the soil. Some place terracotta pots over candles to create little heaters. Probably the easiest but most expensive method is to use electric heat.
One interesting method for insulating a hoop house or high tunnel is to add a layer of bubble wrap under the cover. The sun will store heat in the air bubbles, making for effective, yet inexpensive insulation. Another way to insulate is to use two layers of plastic with a fan blowing air in between.
Some growers use a water tank in a hoop house to store heat from daytime sun. The heat stored in the thermal mass of the water is naturally released during the night, keeping the plants warm. Storing heat in thermal mass doesn’t have to use water. Any thermal mass that will cost effectively store heat will act as a heat battery.
A polytunnel is made of two main components: the frame and the cover. The frame in a backyard hoop house kit will last many years. On the other hand, the cover will typically last three or four seasons in areas that see a lot of snow. Some of the new, reinforced covers will last longer.
In areas where temperatures consistently drop below freezing, you can’t grow vegetables in an unheated hoop house. The night time temperatures will freeze even the hardiest vegetables. You can harvest carrots in winter. In fact, they’ll even taste better, but they aren’t actually growing. Some hardy salad greens (e.g., spinach) will take a few nights of sub-freezing temperatures and bounce back.
Yes a hoop house made from a hoop house kit will survive winter snow. It will mostly slide off. You should, however, remove as much snow as soon as possible. I’ve found, however, that it helps if you have reinforcement where there’s a lot of space between the hoops. One way to do this is to run electrical wire horizontally across the hoops. Another way to provide extra support is to prop wood boards running from the ground to the plastic. This will work as a backstop and add extra support to areas where there is a lot of space between the hoop.
You don’t need artificial lights in a hoop house in most areas. One of the big benefits of starting seedlings in a hoop house is that, during the day, it’s warm enough even when it’s cold outside. This allows you to take advantage of the sun’s powerful light.
You can easily move a hoop house that is made from a hoop house kit. Typically, two people can move it in a few minutes. This comes in handy when you are having some difficulties with the soil inside the hoop house. You can just move it instead of replacing the soil.
Many vegetable plants grow better in a highly humid environment. A hoop house or high tunnel captures both heat and humidity. This makes for an improved growing environment for tomatoes and other heat and humidity loving plants.
You need to harden off plants that you have started in a greenhouse. Why? Because hardening off allows your plants to adjust to the new amounts of wind, light and cold in the great outdoors. But plants will need less adjustment when coming from an unheated hoop house. This is because the amount of light is close to the amount plants would get outdoors. The temperature also is about the same. However. there usually is more wind. So you should still harden off your plants. But you can be a little more aggressive in how quickly you transplant them.