What information can you give me on greenhouse strawberry production?
N.S.KentuckyAnswer: I am pleased to provide you with information on greenhouse strawberry production. In North America, greenhouse production of horticulture crops has been somewhat limited primarily to tomatoes and greens. Many consumers in the northern part of the country can get fruits year round; however, they tend to be not freshly picked. In recent years the fruit market has taken popularity among growers and consumers. Rather than strawberries picked before peak harvest, it is possible to produce strawberries in the winter, in a greenhouse. 100 years ago, Liberty Hyde Bailey found success in forcing strawberries to grow in greenhouses. Since then, many varieties have been readily available and are more productive. Cornell University has identified some of the most productive and flavorful varieties today and have focused their research on getting them to fruit during the off season (Pritts, 2000). Tristar, a cultivar developed by Maryland, was found to produce the highest yields and was the most flavorful variety in a study conducted in 2000.Many factors need to be addressed to successfully grow strawberries in a greenhouse. Overwintering, lighting, heating, fertilization, irrigation, pollination, and pest management are just a few. In relation to overwintering, the study conducted by Cornell University planted strawberry crowns into 6 inch pots filled with peat, perlite, and vermiculite in May and June, and continued to grow them outdoors through November. Plants were then moved into the greenhouse or a cold frame at about 28-30 degrees Fahrenheit. At staggered intervals, plants were taken out of the cold frame about 12-12 weeks before fruit was desired. For adequate establishment, the plants were deflowered and de-runnered for the first two weeks in the greenhouse.Because much of North America is cloudy during the winter, supplemental lighting is required at night to provide additional day length. In trials performed at Cornell, supplemental lighting was provided from 2200 to 700 hours (10:00 P.M. to 7:00 A.M.) with high pressure 400 W sodium lamps. Since strawberries prefer lower temperatures than most plants, heating of the greenhouse is required only at night and heat from the lamps is adequate to produce the high temperatures during the day. The day/night temperature recommended by Cornell is 75/55 F. Greenhouse production of strawberries has successfully done by both hydroponic systems and in a soil culture. What Cornell found was that for soil culture, 50-100ppm N was adequate for strawberries. Additional boron might be required if leaf levels drop below 30 ppm. Phosphoric acid can also be added to maintain an optimum pH level of 5.8-6.5.The other big issue when it comes to greenhouse strawberry production is pollination. Strawberry flowers require some type of assistance to move the pollen from the anthers to the stigma. Instead of using honey bees or performed the daunting task of hand pollination, bumble bees are used to provide pollination for the strawberry plants. Bumble bee hives are short-lived, and thus need replaced every 6-8 weeks. For more bumble bee information, refer to the list of vendors provided below. If bees are used for pollination, pesticides are not recommended to control the number of greenhouse pests such as fungus gnats, two-spotted spider mites, aphids, thrips, powdery mildew, and gray mold. Instead, biological control agents are introduced into the greenhouse before a pest outbreak begins. Therefore, it is essential to scout for pests and secure an efficient mode of action. References:Jett, Lewis W. 2006. Growing Strawberries in High Tunnels in Missouri.Pritts, M. 2000. Berried Treasures: Off-Season Production of Strawberries and Raspberries. Department of Horticulture. Cornell University. Vendors Who Import them from Holland or CanadaGB Systems P.O. Box 19497Boulder, CO 80308OrGB Systems P.O. Box 300Locke, NY 13092(315-497-3129)The Green Spot93 Priest Rd. Nottingham, NH 03290(603-942-8925)