Treating strawberry plants as annuals — planted, harvested and destroyed within a 12-month period — provides uniform plant stands unaffected by summer disease, drought or weed competition, as well as earlier fruit harvest, larger berry size, heavier yield potential, and shorter turnaround time from planting through harvest (eight months).
Initially used by growers on the West Coast and later refined at North Carolina State University, this method is known as the annual plasticulture system.
Noble Foundation horticulturist Steve Upson and Oklahoma State University research and Extension horticulturist, Lynn Brandenberger recently completed a study of strawberry annual plasticulture at the Foundation's Horticulture Center.
“The study evaluated the performance of several commercial strawberry varieties using the annual plasticulture system,” Upson said. “Another objective was to determine if strawberry transplants produced in Oklahoma could compete with Arkansas-grown transplants in terms of yield and fruit quality.”
Six varieties — Chandler, Gaviota, Jemstar, Camarosa, Sweet Charlie and Festival — were selected either for current industry use as a plasticulture variety or as potential for use in this system. Treatments consisted of Oklahoma- and Arkansas-grown transplants of each variety with the exception of Festival, which could not be obtained from the Arkansas nursery.
The study site consisted of 22 permanent beds, 40-inch by 30-foot, on five-foot centers. The beds were equipped with drip irrigation and covered with black plastic mulch. Transplants were set Oct. 1, 2001. Harvest began April 22 and ended May 17.
All Arkansas-produced Jemstar and most of the Gaviota transplants died shortly after transplanting. Death loss of the Oklahoma-produced transplants was insignificant. Oklahoma-grown transplants out-yielded Arkansas-grown transplants regardless of variety.
To be fair, researchers said, Arkansas transplants were in poor condition when received. According to Brandenberger, the plants had been treated for a fungal infection at the nursery but still appeared to be sick.
“Considering the condition of the Arkansas transplants, the yield differences are not surprising,” Upson said. “Results suggest that only the best quality, disease-free transplants should be used in the plasticulture system.”
Considering results from Oklahoma-grown plants only, Chandler ranked first in marketable yield while Gaviota ranked last.
For many years, Chandler was the strawberry variety of choice among plasticulture growers on both the East and West coasts. Recently, Camarosa replaced Chandler as the preferred variety, based on equivalent yield potential, superior fruit characteristics and greater resistance to anthracnose. In the Foundation study, however, Camarosa yields were only two-thirds of Chandler.
Even more surprising was the performance of Jemstar, which ranked second in marketable yield (just behind Chandler) and first in average fruit weight.
Just as impressive was Jemstar's consistently large berries throughout harvest. The berry size of Jemstar was 0.64 ounces per fruit, and in a taste test conducted at the Foundation, Jemstar ranked first in both berry appearance and flavor.
The results of the study should not be considered conclusive, Upson cautioned. Growing conditions and pest populations change from year to year, and additional trials need to be conducted over several years before either the Foundation or OSU can recommend any variety with a high degree of certainty.