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L.E. Trenholm and J. Bryan Unruh2 1. This document is ENH14, one of a series of the Environmental Horticulture Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Original publication date August 2001. Revised December 2010. Visit the EDIS website at http://edis.ifas.ufl.edu. 2. L.E. Trenholm, associate professor and turfgrass specialist, Department of Environmental Horticulture, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611, and J. Bryan Unruh, professor, West Florida Research and Education Center, Institute of Food and Agricultural Sciences. In many parts of Florida, lawns go dormant in the late fall and early winter. This results in a brown lawn throughout much of the winter. While this is a natural process and there is nothing wrong with the grass, many homeowners prefer to have green lawns year-round. A practice called overseeding is often used to provide green cover through the winter months. In overseeding, a temporary cool-season grass species is seeded over the permanent warm-season lawn. Grasses used for overseeding die out in the spring when the warm-season grasses come out of dormancy. Ryegrass is the best choice for overseeding home lawns. Ryegrasses (annual, intermediate, and improved/perennial) are popular because they are reasonably priced and provide: Rapid seed germination Fast growth Adaptability Tolerance for sun or shade Tolerance for close, frequent mowing Dense cover throughout the winter Annual ryegrass is a coarse-textured grass with leaves measuring 5 mm wide. Leaves are medium green in color. It germinates and grows very quickly but is prone to die in drought conditions and when temperatures exceed 80FF. Annual ryegrass is approximately one-third the price of perennial ryegrass. Perennial ryegrass is a much finer-textured grass, with darker green leaves measuring 2 mm wide. It persists longer in the spring and is not as prone to drought and temperature extremes. Perennial ryegrass is approximately three times the cost of annual ryegrass. Intermediate ryegrass is a hybrid between annual and perennial ryegrass. It possesses characteristics of both species. Ryegrass dies out in spring as temperatures rise, when permanent lawn grass should be actively
Overseeding Florida Lawns for Winter Color 2 growing again. Ryegrass must be reseeded each fall to provide a green winter lawn. It is best to wait until daytime temperatures are consistently in the lowto midseventies Fahrenheit. Seedling survival is reduced if seeds are planted during warmer periods. For North Florida, lawns should be seeded from October to early November. For Central Florida, overseed from October to early December. In frost-free areas of South Florida, lawns generally do not go dormant, and overseeding is probably not necessary for winter color. The two most important steps in overseeding are proper seedbed preparation and proper watering. To prepare the lawn for overseeding, rake the grass thoroughly to remove all debris. Next, mow the lawn at a lower height than usual. For St. Augustinegrass lawns, do not mow lower than 3 inches. Catch all clippings or rake the grass afterwards. The lawn may need to be cut more than once to reduce it to the desired height. The overseeded grass seed must be able to contact the soil for optimum performance. A final raking removes additional material and loosens the soil so the seed can come in contact with the soil. Heavy thatch causes uneven seed germination and cover. Lawns with heavy thatch should be dethatched in spring or early summer if fall overseeding is planned. Dethatching with a power vertical mower or power rake (these can be rented) is advisable. For more information on thatch, please refer to Thatch and Its Control in Florida Lawns (http://edis.ifas.ufl.edu/lh029). The next step is seeding. Rates listed in Table 1 produce reasonably good color and density. If a thatch layer exists, increase seeding rates 25%%. If available, buy fungicide-treated seed. For best coverage, use a broadcast spreader. If using a drop spreader, make sure to overlap an appropriate amount to avoid skips in the overseed. To establish a very uniform stand, sow half the seed by walking in one direction, and the other half by walking at right angles to the first. After seeding, rake the ground with a stiff broom to ensure the seed gets through the grass and is in contact with the soil. Watering is the last but most important step in establishing a winter lawn. Seeds will not germinate without moisture, so it is critical to follow appropriate irrigation practices. Water should be applied lightly (10 minutes) to the overseeded lawn once or twice a day until the seeds have germinated (generally 7 days). Daily watering should continue for 2 weeks to apply about 1/4 inch of water each time until seedlings are well established. Do not overwater. Overwatering washes seed away and encourages disease development. Once the plants are well established (e.g., mowed several times), water as needed to prevent wilting. Once a winter lawn is established, it requires the same maintenance as a permanent lawn. This includes mowing, watering, fertilizing, and pest control. Mowing should begin when the overseeded grass is well rooted and tall enough to be cut (about 1 inches above the permanent grass). Properly fertilized ryegrass grows very quickly, so weekly mowing is often required. Be sure to have mower blades sharpened to properly care for the overseeded grass. Water as needed to keep the grass from wilting. Fertilize to keep the ryegrass healthy and growing vigorously through the winter. To help prevent root burn, the first fertilization should follow the second mowing. Apply a lawn fertilizer at a rate of no more than 1 lb of nitrogen per 1,000 sq ft of turfgrass. For more information on
Overseeding Florida Lawns for Winter Color 3 fertilizing, please refer to Figuring Out Fertilizer for the Home Lawn (http://edis.ifas.ufl.edu/ep221). A second fertilizer application can be made approximately 60 days later. Always follow Best Management Practices when fertilizing to reduce any potential nonpoint source pollution from the misapplication of fertilizer. Ryegrass is very susceptible to a disease called pythium. For more information, please refer to Pythium Blight on Overseeded Turfgrass (http://edis.ifas.ufl.edu/pp124). The disease appears most severely on overwatered, overfertilized ryegrass, especially during warm, humid weather. Using fungicide-treated seed, seeding during the coolest months, and watering and fertilizing properly may help prevent the disease. Fungicide applications may be necessary and should be done quickly if symptoms occur. For disease control recommendations, please refer to Homeowner's Guide to Fungicides for Lawn and Landscape Disease Management (http://edis.ifas.ufl.edu/pp154). To encourage growth of permanent lawn grass in the spring, do not encourage the overseed grass to continue growing in the spring. The permanent lawn grass can be weakened by the highly competitive ryegrass during this overlapping season of growth. Ryegrass normally dies out in late spring, but if the weather is cool and the lawn is watered frequently, it can persist. To discourage the ryegrass, do not apply fertilizer after February in South Florida, or after March in North Florida. Water as infrequently as possible, while making sure the permanent lawn grass does not suffer from drought. Continue to mow the ryegrass as closely as possible each week. These practices tend to weaken the winter grass and facilitate a faster transition back to the permanent lawn grass. Once the permanent lawn grass has resumed growth, begin a regular lawn maintenance program. Overseeding provides green winter turf cover. Overseeding is primarily used on golf courses, athletic fields, and high-profile landscape areas, but the principles can be applied by homeowners wishing to have year-round green lawns. It is important, however, to remember that this practice involves year-round lawn maintenance, including fertilization, irrigation, and mowing. Be sure to be ready for increased maintenance. Lawn with irregular patches of overseeded grass. A heavy thatch can lead to a lawn with irregular patches.
Overseeding Florida Lawns for Winter Color 4 Overseeding rates for home lawns Bluegrass 3 Fescue 7 Ryegrass (annual) 10 Ryegrass (intermediate) 10 Ryegrass (perennial) 10-20