Strawberries can be a challenge to grow, but success is oh so sweet
West Central Florida - particularly the area around Plant City - is one of the most important winter strawberry growing areas in the world. But although farmers produce berries by the bushel, they also have a lot of sophisticated tools for dealing with problems. Growing strawberries in the home garden can be a challenge, but it's not impossible. If you're up for giving it a try, here are some tips to help ensure your efforts bear fruit. Varieties "Sweet Charlie" and "Festival" were developed at the University of Florida's Gulf Coast Research and Education Center in Hillsborough County and are well-adapted to the climate of the Tampa Bay area. These varieties produce attractive, flavorful berries and are capable of producing 1 to 2 pints of fruit per plant over the season.Sweet Charlie is available from Lewis Nursery in North Carolina, (910) 675-2394. Their minimum order is 100 plants, which cost $40 plus shipping and handling. Festival should be available at Parkesdale Farm Market in Plant City, (813) 754-2704, starting in October. Parkesdale sells plants in bundles of 25 for $5.98. Some local nurseries and the big box garden centers may have strawberry plants for sale this fall, but be aware that they could be selling a variety that is not well adapted to our climate. For a list of nurseries specializing in strawberry plants visit www.ncstrawberry.org/docs/2009PlantSourceList.pdf. Planting For the best combination of fruit quality and yield, plant in mid-October. Strawberry plants need at least eight hours of direct sunlight a day. If a full sun location isn't available, try to choose a spot that's sunny during the morning and early afternoon. The soil should be well drained and slightly acidic (pH 5.5-6.5). Most strawberry plants grown in Florida are planted in double rows, with plants spaced 12 to 15 inches apart. Strawberry plants also can be grown in planter boxes, strawberry pots, hanging baskets, and other types of containers. Mulch around the plants helps to control weeds and keeps the fruit cleaner than if it were lying directly on the soil. Bare-root plants are the most common type of transplant available. Those with leaves on them generally produce greater December yield than those without leaves. The former, however, require frequent sprinkler irrigation from about 10 a.m. to 5 p.m. for the first one to two weeks. Another type of transplant is the plug, available in plastic trays or in small pots. It requires very little sprinkler irrigation to establish. Regardless of the type of transplant used, it's important not to set the plant too deep - covering the crown - or too shallow, leaving roots exposed. Once the plants are established, apply 2 pounds of 10-10-10 (or equivalent) garden fertilizer with micronutrients (including boron) per 10 feet of row. About half of the nitrogen in the fertilizer should be in a slow release form, such as a sulfur- or resin-coated material. Place it in a narrow trench about an inch deep between the two rows of plants. An alternative is to periodically apply liquid fertilizer. Problems Strawberry flowers and fruit can be damaged when the temperature drops below freezing. Protect the flowers by covering the plants with old sheets or a commercial polypropylene row cover during the afternoon before the expected freeze. Anchor the covering so it doesn't blow off. Pests are another threat, and a key to managing them is to start with healthy transplants - plants free of leaf diseases, spider mites and nematodes. The odds are better for plants purchased from a reputable nursery or garden center. To control most fungal diseases on leaves, flowers, and fruit, apply captan or thiram weekly, starting as soon as plants are established. Removing old, diseased leaves may help reduce future leaf and fruit infections. Powdery mildew, a fungal disease that results in leaf distortion and powdery white patches on the underside of leaves, is usually controlled with several applications of sulfur. Apply only when it's cooler than 80 degrees so the leaves and fruit won't burn. The type of pests feeding on strawberry plants changes as the season progresses. In October and November, various caterpillars ("worms") are often found feeding on crown, leaf, or young flower tissue. Applications of Bacillus thuringiensis insecticide such as Dipel are usually effective. Later in the season, aphids and flower thrips may cause damage to developing fruit. Malathion can be used to control these, although, given enough time, natural predators and parasites will usually take care of the problem. Spider mites - tiny arthropods that suck juices from plant leaves - are a more persistent pest on strawberries in Florida than are insects. Start examining plants for spider mites in early December, looking for plants with pale yellowish-green leaves. A magnifying glass can be used to see the mites moving about on the underside of leaves. Several miticides are labeled for use on strawberries in Florida, including fenbutatin-oxide (Vendex) and dicofol (Kelthane). They're most effective when applied twice, about five days apart. When using miticides or any other pesticides, be sure to read and follow all label directions. Parasitic nematodes (microscopic round worms) and certain soil diseases can cause problems if strawberry plants are set in the same area year after year. Avoid planting strawberries in areas where you have just grown tomatoes, peppers, potatoes or eggplant. Sweet corn is a good crop to plant between strawberry crops. Solarizing the soil during the summer before planting can also help cut down on soil-borne pests. Your fruit is ready for harvest when three-quarters of it is red. The fruit starts to deteriorate soon after it has become totally red, so it's best to harvest every two to four days.
Craig Chandler is a professor of horticultural sciences at the University of Florida's Gulf Coast Research and Education Center in southern Hillsborough County.