1994 Annual Report for FS94-013
Plant Shelters to Extend the Growing Season for Herbs
Summary
A limited growing season in the mountains of western North Carolina prevents the production of quality herbs beyond the summer months. The region produces high quality herbs, but the limited growing season forces growers to become only part time producers with diminished opportunities for financial return. The normal growing season for herbs, June through September, is also the period of highest labor use and lowest price return for their labor.
Few small producers can afford the initial investment or operational expenses of greenhouses. A solution to this barrier is the development of small scale, affordable and portable plant shelters to extend the growing season of specialty crops in the mountains.
The growing season of several herb plants could possibly be extended (through the use of shelters) from the late frosts of April and May to the early cold snaps in September and October. Portable shelters placed in the fields at planting time could possibly sustain a growing season of eight months instead of four months. Such an extended season has the potential to triple the income from a given number of plants or production area due to premium prices being paid during months that herbs are usually not available.
Objectives
1.) Develop and test plant shelters designed to extend herb growing season.
2.) Host a field day and/or workshops to demonstrate the use of plant shelters to extend the herb growing season.
Approach
The project aimed to design shelters that were lightweight; portable; inexpensive to construct, maintain and store; easy to operate, energy efficient and re-usable for several seasons. The shelter system was also designed to have a drip irrigation component to accommodate the extended growing season and periods of drought.
The success of the shelters was to be measured by the extended length of the growing season, the increased supply of herbs harvested and sold through the market cooperative and the financial return to the farm. Records were to be maintained to demonstrate the cost effectiveness of the shelters and irrigation system.
Results
Field tests conducted in this project did not identify any construction materials or designs that performed adequately for commercial production of herbs. All of the designs used greenhouse plastic stretched over frames made of various materials. The frames were 12 feet long, 4 feet high and 6 feet wide. They were sized to fit over two greenhouse rows when the plants were young and one outside row when the plants were transplanted.
The first materials evaluated were 3/8-inch metal pipe and 2-inch locust saplings. Both of these materials resulted in structures that were too heavy to be portable.
They were cost-effective for this producer because he obtained used pipe at a very low price and cut the locust saplings from his own property. In his opinion, if those materials had to be purchased at a greenhouse supplier the cost would be comparable to building a new permanent greenhouse, making those materials cost prohibitive.
Rectangular shelters constructed of 3/4-inch PVC pipe showed promise in that they were lightweight, portable and inexpensive. However, when subjected to high winds they blew over and damaged the plants. At that point inexpensive, reuseable anchors were evaluated. Again, locust saplings were cut from the producer’s property and used in a manner similar to tent stakes. However, they had to be pulled out of the ground in order to move the shelters or open the plastic covering for venting on sunny days.
A second set of PVC shelters were made in quanset hut style with the pipe bent into hoops four feet high and six feet wide at the base. They failed to survive the winter as the bent piping shattered due to a combination of pressure and low temperatures.
After the hoop design, a triangular PVC frame was tried, but it sacrificed too much room, especially head room, to be practical.
To other farmers considering the use of portable shelters, this producer suggests they may try PVC pipe made into rectangular frames with, perhaps, a heavy gauge wire for anchors.
He also suggests they may look into herbs that have a lower growing pattern than basil. Since basil requires a frame about four feet high, most any material that would be light enough to be portable would also be subject to blowing over in windy conditions. If basil is the herb of choice, then shorter frames (24 inches) could be used to extend the beginning of the growing season while the plants are still small, but would be useless to extend the end of the season when the basil matured.
The irrigation component did not ever reach testing stage as a flood in 1994 washed out part of the irrigation system and another storm in 1995 washed out the stream intake, delaying installation until mid-summer. Then a road construction project upstream deposited mud into the stream, clogging the drip pipes so that no irrigation was possible during drought season.
During the project, market prices for this producer’s herbs dropped due to the unexpected availability of inexpensive herbs from Mexico, Israel and Australia. His normal price of $5 per pound for basil dropped to $4 per pound, and he still could not compete with prices of $2.50 per pound, which caused him to leave much of his crop unharvested. With inexpensive imported basil becoming available year-round, he now considers it unlikely that he will invest in irrigation systems or shelters or even remain in the culinary herb business. He and other North Carolina growers are concentrating on medicinal herb production.
Outreach
There was never an opportunity to demonstrate a working system in this project due to the design weaknesses in the frames and to the irrigation system problems. The producer made a presentation to the local high school agricultural students where the students had an opportunity to suggest design and material ideas for the portable shelters. The producer gave several tours to people who learned of his operation through the Extension agent.
December 1995.