Growers in upstate New York are getting big yields and hitting new market windows by producing their crops in high tunnels, structures consisting of a metal frame covered by a single layer of polyethylene. “A cheap man’s greenhouse,” is how Cornell University Horticulture Professor Hans Wien, who led a recent research project on high tunnel usage, terms them. A standard single-bay structure 100 feet long and 20 to 30 feet wide would run from about $5,000 to $7,000.
The chief benefit of high tunnels is that they allow growers to extend the growing season by about 10 weeks, half in the spring and half in the fall. The tunnels are used to produce a variety of crops, including peppers and cucumbers, but tomatoes are by far the most popular. “They respond well to the environment because they can grow vertically,” says Cornell Extension associate Judson Reid, who works directly with many growers. “They intercept the sunlight vertically.”
Besides allowing growers to get to market earlier with high-quality produce, high tunnel yields can be huge. A single 2,000-square-foot high tunnel tomato crop may yield 7,500 pounds of tomatoes, potentially paying for itself in a single year. There are reasons, after all, why high tunnels have been popular in Europe for many years. But before investing in a high tunnel, Reid and Wien caution that there a number of factors for growers to consider. Here are eight:
• Market. First, consider how and where you are going to sell your product, says Reid. “You need to know a current market where you can sell it,” he says, “or you need a new market.” Wien warns against simply checking out local farmers’ markets. “Go to the nearest cities,” he says. “In our case, it would be Rochester, or even New York City. Find out what’s needed, and grow that.”
• Crop Selection. Tomatoes have proven very profitable, but they’ve become almost too popular, leading to disease problems, says Wien. “The temptation is to grow tomato after tomato after tomato,” he says. “If you leave your tunnel in one place you’re asking for trouble. You need some crop rotation.” Not only can you help avoid disease problems, but there could be some lucrative alternatives, such as ethnic vegetables, says Reid, adding that growers don’t have to limit themselves to vegetables.
• Location. Don’t forget that high tunnels are usually pretty flimsy, just 6 mm of polyethylene, so wind can be a big problem, says Wien. “Try not to site it on the top of a hill,” he says. “If you grow in an area known for high winds, this might not be a technology that works for you.”
• Equipment. Another potential weather-related problem is snow. Late snows that can hit the Northeast around transplanting time in early April are often heavy in moisture. Cheaper tunnels will usually have wider spacing between hoops, Wien says, making them more vulnerable to collapse from a heavy snowfall. “If you’re tempted by the low prices for some high tunnels,” he says, pausing, “well, you get what you pay for.” Another thing to keep in mind when selecting a tunnel is that while most are designed to be permanent, some can be moved, which would be beneficial if you were determined to grow continuous tomatoes, for example.
• Fertilization. Another equipment concern is whether to install an injector for your fertilization system. Just do it, Reid says. Tomato plants grow so quickly that they will use twice as much fertilizer as they would if grown in the field, and they should be spoon-fed.
• Water. Fast-growing crops also require a lot of water, says Reid, noting that a high tunnel tomato plant drinks a gallon a day. “And there’s no rain in there,” he says, so you’ll need access to a lot of good-quality, reasonably priced water.
• Pests. The good news is that the tunnels provide some protection against many pests commonly found in the field, says Wien. The bad news is you may well encounter new pests in the dry environment. “For example, in New York spider mites are not a problem on tomatoes in the field,” says Reid. “But they’re a big problem in high tunnels.”
• Labor. High tunnels are very labor intensive. Pruning, trellising, and harvesting are all more frequent in the tunnels, plus there’s the added headache of ventilation to avoid potentially enormous temperature swings, says Reid. “What keeps more people from jumping into this is it takes careful watching,” says Wien. “You have to be around.”