Before You Buy A Hoophouse Or High Tunnel
Hoophouses and high tunnels are more popular than ever for farms and home gardens. A hoophouse is a greenhouse usually heated only by the sun. Hoophouses are usually made with steel bows and covered with plastic. They are generally built without concrete footings and used for growing crops in the ground.
Hoophouses stay warmer than outside and protect crops from wind and rain. This helps to prevent stress and reduce pressure from fungal disease. Hoophouses allow fruits and vegetables to grow at times usually out of their regular growing season. They even allow cold-hardy crops to grow through the deep winter. High tunnels create a microclimate that simulates the temperatures of a location several hardiness zones closer to the equator.
Benefits for Crops and Farms
Many crops benefit from the protected space of a hoophouse. For fruiting crops like tomatoes, cucumbers, and peppers, keeping rain off leaves and fruit can prevent disease such as blights and mildews. In the warm season, leafy crops are safe from wind stress, and may benefit from the slightly reduced sunlight that the plastic film provides.
Improvements to crops within hoophouses often extend to resilience for farms. Farmers know they will have relatively healthy crops in a high tunnel despite the risk of a cool or wet season damaging their outdoor crops.
High tunnels (with the right practices) can extend the harvest season through the winter. Even in the north, cold hardy vegetables such as greens, roots, and herbs can be planted in the fall to reach maturity before the deep winter. Most crops will not get enough light to grow much during the deep winter, even in a hoophouse. With the right timing, though, they may be harvested on days when there is enough sun to warm the hoophouse and thaw plants before harvest.
Many growers find that keeping a harvest of fresh produce during the winter lets them keep supplying the customers they have reached during the summer. Restaurants and grocery stores can continue their “locally grown” marketing campaigns, and consumers are able to maintain relationships with farms they buy from.
Choosing a Hoophouse Site
Flat – not necessarily level
When using the proper tools, such as a laser level, a hoophouse can be tilted to match a slope. It is more important that a high tunnel site be flat than level.
If the site slopes evenly only to drop away more steeply, the baseboards of the hoophouse will be left above the ground and will need to be backfilled. If it is flat except for a raised area, the higher area will need to be trenched along the ground posts to accommodate baseboards.
It’s disappointing and costly to invest time and energy into crops just to watch them stress out in waterlogged soil.
Due to the cost of building high tunnels relative to growing in outdoor fields, take care to make the space as productive as possible. A hoophouse is valuable real estate! Drainage issues should be fixed before the tunnel is built.
A savvy grower will understand how water moves through the surrounding soils and will consider the hydrology of the whole farm. Perforated drainage tile beside the baseboards can move water away, and diverting water upstream from the hoophouse can preclude any problems.
Hoophouses are best placed where they can capture the most energy from the sun. In the northern hemisphere they should be built away from any tall objects to the south. Shadows are longer during the winter months – at noon on the winter solstice at 40° the shadow of an object will be twice as long as the object is tall.
Snow can accumulate quickly when it is heavy and wind driven. If high tunnels are built too close together, a snowdrift on the leeward side of one structure can grow large enough to reach the next one. Room should be left for snow as well as access needed to remove it if necessary. At least twenty feet should be left between structures in areas with heavy snow.
Building the length of your hoophouse from east to west is best suited for year-round growing at nearly all latitudes. This orientation receives greater energy from the sun in the winter, and less in the summer, except for very near the equator. Other factors are important too, though. Its best to understand the direction of prevailing winds and their wear effect on flat endwall materials, as well the wind’s ability to produce damaging snowdrifts.
Preparing A Hoophouse Site
Preparing The Grade
Hoophouse builders can work with some variability in your grade and hiring a contractor with a bulldozer can be expensive. That said, not grading can be even more expensive. You should understand the cost of improving the ground versus the cost of slowing the building process. Also remember the future cost of issues of a skewed building site in the future.
Preparing The Soil
It is much easier to prepare the soil on a hoophouse site before building. The soil can be worked with a rototiller or other tillage tools, or sod and ground cover can be killed using tarps. Deep tillage with a chisel plow, subsoiler, or broadfork can create a soil structure more suitable for plant growth. Baseboards are set into the soil to create a seal around the edges of the high tunnel. When sod is left intact beside ground posts it adds to the install time as a shallow trench will need to be dug through the difficult sod to set baseboards into the soil.
Amending Hoophouse Soil
High tunnels are valuable real estate! Be sure that your plants have what they need to stay healthy. Many growers add several inches of compost to the soil when establishing a new hoophouse. It is much easier to get a dump truck’s worth (or several) of compost on your site before the hoophouse is built. Compost and well water are often alkaline, which means that their pH is higher than what plants ideally like to grow in. Test your soil pH and nutrients often. If you notice the pH of your soil climbing, you can use sulfur or aluminum sulfate to lower it back down to the ideal level.
Types Of High Tunnel
Gothic-style hoophouses have a pointed arch profile to the bows. They are an excellent choice for areas with heavy snow. The steeper slope of the roof allows snow to slide off more easily. Gothic-style high tunnels also allow more sunlight to penetrate in the winter.
Quonset hoophouses use rounded bows. They are usually the least expensive high tunnel structures to build, although the rounded roof line of the bows can allow for more snow to build up. The bow profile also provides less room to maneuver equipment within the hoophouse and to work near the edges of the structure.