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Leah Fronk
Horticulture Educator
Penn State Extension
Juniata County -- Reading the most recent weather outlook from the Penn State Climate Office, long range guidance suggests seasonal temperatures and precipitation above normal for the remainder of July. The precipitation is a welcome change for most parts of the state that were in a deficit, or continue to be in a deficit, during the months of May and June. While disease pressure is lower during dry weather, no precipitation for weeks gives pause for concern. Another issue that pops up during dry weather is weed control. Most weeds can prosper in any type of weather. Regardless of the type of weed (annual, biennial, or perennial), they have exceptional adaptability when it comes to growing and germinating in variable weather conditions.
The main reason for writing about weed control is that many strawberry growers are considering whether to carry-over their strawberry plantings to next season. Because of the dry weather this spring, disease pressure was low, and plantings may be good candidates for renovation. Typically, matted row (straw mulch) plantings are left in place for 2-5 years. Gardeners who use plastic mulch may only grow for 1 or 2 years depending on winter injury. You as the gardener know your crop best and must think about the integrity of the plastic, time spent to remove runners, and clean-up of dead plant debris around the crowns. And of course, weed control is an issue in strawberries whether you are growing matted-row or on plastic since good weed control is very important to improve yield and reduce disease pressure.
The first step in renovating your strawberry patch is mowing off the plants. In small strawberry patches, you may cut off plants with a string trimmer or hand shears. If weeds are growing over and above the strawberry plants, it may be a good idea to spray with 2,4-D amine prior to mowing. Give yourself a 7-10 day window for the herbicide to take hold, and then mow the plants off. Mowing helps to reduce disease inoculum and promote the plant to grow new leaves and fruit buds for the next season. Care must be taken not to damage the crowns.
After mowing, apply a granular or liquid well-balanced fertilizer such as 20-20-20 or compost alongside the plants. For home gardeners, you may follow the directions on the fertilizer bag for application rates. If you suspect nutritional deficiencies, a soil test would be a good idea. Even though soil tests are often discussed in the fall, you can take them at any time of the year. In the case of a strawberry patch, renovation would be an excellent time to pull a soil sample.
If you grow strawberries using straw mulch, cultivate the soil in between the rows to thin the plants out and throw a little soil on top of the crowns. This helps to prevent a carpet of strawberry plants from crowding each other out and the extra soil helps to keep the crown anchored. Defined rows make strawberries easier to harvest. If you notice additional runners at this time, remove them. Narrow each row to about 12 inches. While you are trimming runners, it is also a good idea to remove all the dead plant debris around the crowns. The dead plant material is a good place for plant disease to get a foothold. Gardeners using plastic mulch will skip the cultivating part unless it's for weed control, and simply remove the extra runners by hand.
When growing strawberries in the home garden, you must rely on a combination of manual weeding, mowing, cultivation, and mulching for good weed control. Some annual weeds commonly found in strawberry patches include galinsoga, pigweed, Pennsylvania smartweed, lambsquarter, and purslane. Control with organic burn-down herbicides may offer control for annual weeds that are less than 4 inches tall. However, annual weeds that grow too large, or perennial weeds, will require more effort. Using the plastic mulch system and establishing a low-growing cover crop of white clover in the row middles may be an option if you start with relatively clean row middles.
Do not forget to water your plants for the remainder of the growing season. Even though they will not produce a crop until next May or June, water is necessary for them to use the fertilizer you applied and grow leaves and next year's flower buds. Continue to pull weeds as they grow. Some winter annuals such as dead nettle and chickweed will start growing in early fall and it's much easier to pull them in the fall than in the spring.
Home and commercial growers who have additional questions about strawberry renovation are welcome to email Leah at lxf339@psu.edu. In addition, commercial growers may consult the "Strawberry" chapter of the Mid-Atlantic Commercial Vegetable Production Recommendations for detailed guidance. Home gardeners will find information by searching "growing strawberries psu." Those without Internet access may call their county extension office and ask for a copy to be mailed to their address.