On the vacant lot in Michigan where her childhood home once stood, Carolyn Meekins grows seedlings for Asian greens, red kale and green beans in a plastic-covered greenhouse known as a hoop house.
The structure warms and protects the tender, young plants, allowing Meekins to plant earlier in the year. She was the first in Flint to build one last year, but more urban farmers like her are using hoop houses to extend the growing season in northern U.S. cities.
Hoop houses are relatively inexpensive to build and often are unheated — relying instead on the sun or heat thrown off by compost heaps. With frames made of metal, flexible PVC pipe or wood, they work like greenhouses but are covered with plastic instead of glass. They can be small enough for a city back yard or 100 feet long.
With them, farmers can extend a five- or six-month outdoor growing season to the whole year, said Adam Montri, an outreach specialist with Michigan State University’s Department of Horticulture. And hoop houses don’t need heaters or the costly high-intensity lights often used in commercial greenhouses.
“Northern cities are … seeing the benefits of having them,” Montri said. “As urban agriculture has grown, hoop houses have kind of grown simultaneously.”
Urban farming is on the rise in Flint, where sparsely populated neighborhoods and thousands of empty lots provide space for growing. Meekins began gardening in her neighborhood in 1995, and her Urban Community Youth Outreach farm now includes 11 lots, with rows of vegetables and a wheat field.
Plants started in late winter in the hoop house, Meekins said, will give her an early jump on spring crops for her farm. She also wants her hoop house to be a place where smaller community gardeners can get their starter plants.
“Our plan is to make this a hub of all transplants,” Meekins said.
Commercial farmers in rural areas around the country also use hoop houses, but they make sense in cities, where lots are smaller and yard space is often limited, because crops can be grown close together — or even stacked in layers inside.
“It’s very different than in the field,” Montri said. “What it allows us to do is produce a large amount of food in a smaller space.”
The Detroit Black Community Food Security Network uses a hoop house at its D-Town Farm to grow food that it sells in the city. Former pro basketball player and urban farmer Will Allen’s Growing Power Inc. uses hoop houses in Milwaukee to grow greens. They’re also popping up in Chicago, where increased interest in eating locally grown food has made a longer growing season more attractive.
“It’s very easy to eat locally in Chicago in August. It’s harder to do that in February or March,” said Lisa Junkin, education coordinator at Jane Addams Hull-House Museum, which has a hoop house on its farm.
The cost of a hoop house depends on its size and the materials used. Kits for 8-by-10-foot backyard models start at a few hundred dollars, while larger hoop houses can cost tens of thousands of dollars. Many can be built in a day or two by a group of do-it-yourselfers. Food can be grown in the ground if the hoop house doesn’t have a floor, or plants can be put in pots or raised beds.
Hoop houses are usually permanent structures, but often aren’t strong enough to withstand high winds and can collapse if heavy snow isn’t brushed off. The plastic traps warmth from the sun. In colder weather, composting inside the hoop house can add warmth, since the process throws off heat.
Before building a hoop house, however, urban growers need to check local zoning rules and building codes. Meekins learned this after she started building her hoop house in 2005. The city stopped construction, saying she needed a zoning variance because it was on a vacant lot.
Meekins had expected to spend a few thousand dollars and have a hoop house in a few days. Three years later, the total reached $21,000. Money spent seeking a permit, getting blueprints drawn up to satisfy the city and buying more materials drove up the cost.
If she built another one, Meekins said, the price likely would be much lower.
Once a hoop house is up, farmers find using them is a learning experience — more like growing in a traditional greenhouse than a field. The sides can be rolled up or down to vent air and control the temperature, but it took Meekins a while to learn to do this properly. Her first set of plants died.
“I thought it was supposed to get real hot and I just burned them out,” she said. “I’m strictly a city girl, so I am learning.”