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February 2, 2001

By Lana Robinson
Field Editor

The earlier the better is especially true when you grow and sell high-value vegetables direct. Beating the competition to market and landing those customers who are likely to stay with you all season long is a definite advantage. To get the jump on fellow growers, maybe you should consider hooping it up!

"The hoop house fills a horticultural niche for those growers who sell direct. With the hoop house, you can mediate the effects of low temperature—that unexpected freeze. The primary benefit is earliness, a combination of being able to plant two weeks earlier than fields are planted and faster maturation of the crop inside the house. You can extend your growing season by two months—a month on either end," said horticulturist Steve Upson, who has been conducting hoop house research at the Samuel Roberts Noble Foundation in Ardmore, Okla. for the past four years. "Complementing field production with hoop house production is a win/win strategy for the progressive market gardener."

Upson, who was among the speakers at the annual Central Texas Vegetable Shortcourse in DeLeon last month, cited the advantages of the hoop house over other season-extending technologies.

Hoop houses are generally Quonset-shaped and constructed of metal or plastic hoops (bows) covered with one layer of 6-mil greenhouse grade polyethylene film and ventilated by rolling up the sides. A hoop house has no permanent heating system or electrical connections. The only external connection is the irrigation supply line. The ends of the houses are framed and covered with polyfilm or a rigid material such as fiberglass. Most end walls are fitted with doors; however, a few can be removed entirely, permitting greater access. Hoop houses range in width from 14 to 20 feet and up to 96 feet in length. Compared with greenhouses, hoop houses are relatively inexpensive, ranging in price from $1.25 to $2 per square foot compared to $3.50 to $6 for a greenhouse.

Hoop houses can be permanent or moveable, enabling more efficient use of land.

Storm, wind protection

Traditionally, high value crops such as tomatoes are grown in hoop houses to justify the additional expense. Other crops being grown include strawberries, raspberries, cut flowers, melons, eggplant, peppers, and summer squash.

"Cut flowers make more money than anything else. The key is marketing," he said.

Hoop houses should not be regarded as freeze protection devices, although they can provide limited protection. They do provide storm protection, and, because crops are sheltered from rainfall, there is less incidence of foliar disease in hoop houses.

"Evidently, crows are suspicious enough of the covering that they don't venture inside. If animals become a problem, covering the side vents with a fabric mesh should remedy the situation It's a good idea to have some plastic mesh on hand even if you aren't experiencing animal problems," he advised. "During the spring it makes an excellent windbreak for young transplants."

Upson said temperature management within the hoop house is the single most difficult task. First time growers often underestimate the capacity of the house to gain heat, especially on cloudy days. Because many factors affect heat gain in a hoop house, there are no hard and fast rules regulating ventilation and shade fabric application. Some of these factors include: size of the house; film transparency; condition of film; cloud cover; wind; and calendar date.

Raised beds vs. containers

Upson noted the advantages of raised beds in hoop house production as follows: (1) soil warming; (2) best utilization of plastic mulch (snug fit); (3) ease of harvest; (4) effective soil solarization; (5) limited freeze protection; and (5) site flexibility.

"All of our beds are bordered by 1-by-6-inch treated lumber or equivalent sized rubber lumber, eliminating the need to reform the beds. Beds are 40 inches wide on 5-foot centers. Each bed (loam and compost) runs the length of the house," he said. "Our 17- and 20-foot-wide hoop houses contain three and four beds, respectively. The outer beds are purposely located close to the house sides to facilitate spraying and harvesting from outside when the house is fully vented.

"We use two lines per bed to allow enough lateral movement of water," he explained. "I recommend drip-in emitter over T-tape. It has a 10-year life and is more versatile in a hoop house than T-tape. The hard hose will run you 10-12 cents per foot."

Next the surface of each bed is firmed with a turf roller and watered. Afterwards, plastic mulch is applied. A soil thermometer is inserted through the plastic to record bed temperature. To encourage earliness, transplants grown in 4-inch pots are used. Planting holes are prepared with a posthole digger. A starter fertilizer solution is applied at planting.

As the crop matures, support structures are added and supplemental nitrogen is applied via the drip system per tensiometer readings.

Beds inside a hoop house are not subject to leaching by rainfall. Thus, yearly monitoring for salt build-up is recommended. Upson suggested soaking beds by using a sprinkler or water wand before soil solarization.

Upson experimented with containers, which do cost more and require more water. However, you can remove containers to deal with pests and when a crop is finished and move in the second crop without the down time associated with raised beds; and utilize vertical space.

To ensure earliness, Upson advised growers to: maximize degree days; use early maturing varieties; large transplants; minimize plant stress; and don't overheat or overwater.

"Also, don't scrimp on bees. You need them for pollination, and they will find their way into the hoop house through the vents," he said.

For more information on the economics of hoop house production and step-by-step instructions, call 580-223-5810; email sdupson@noble.org; or visit the Foundation's website: www.noble.org.