Winter Overseeding

By John L. Cisar, Professor of Turfgrass Management and Water, FLREC, University of Florida

 

This man is overseeding the lawn using a broadcast spreader by Lesco. Some spreaders, like this one, can also be used to distribute fertilizer in addition to spreading grass seed. Overseeding should usually be done two weeks prior to the first frost in high elevation areas or when soil temperatures reach about 65 to 70????? F.

Fall is the time to overseed lawns and fields for winter green color, to establish protective covers for warm-season grasses, and to provide acceptable playing sports surfaces. If green swards are on your agenda of things to do before hibernating for the winter, it?EUR??,,????'???s not too late to prepare and seed cool-season turfgrasses. Typically, warm-season turfgrasses stop growing and turn brown after the first hard frost of fall. Even in subtropical areas like the deep south, species like centipede and St. Augustine are not at their best in winter and are particularly susceptible to chilling and cold damage. Bermudagrasses generally go dormant over the entire winter season and do not begin to revive until temperatures reach the upper 60s in late spring. So if a green winter lawn is important or if the big game is around the corner, it?EUR??,,????'???s now or never to overseed.

Fall is the time of year for overseeding which provides green turf during the winter months (if the turf isn?EUR??,,????'???t covered with snow!) and acts as a protective cover for warm-season grasses.

Year-Round Management With Overseeding In Mind

Ideally, preparation is year-round. Keeping your base warm-season turf is the key to a successful overseeding and spring recovery. Before the warm-season turf goes dormant, proper fertilizing, watering and soil preparation is essential. Pre-plant soil-based applications of lime, phosphorous and potassium will help to protect the base grass from cold injury and promote the rooting of overseeded turf. Lime helps to correct soil acidity and brings the reactive soil pH to the optimal zone for growing turfgrasses (pH 5.5-6.5). Phosphorous is associated with rooting and seed establishment. Potassium is important for improving cold and winter desiccation tolerance of both cool and warm-season turfgrasses, and for improving wear tolerance of overseeded athletic field turf. Moreover, reducing the N:K ratio in your turf fertilizer will help reduce the competitiveness of bermudagrass and other warm-season grasses without compromising the heath of the turf.

Overseeding Timing

The best time to overseed is when the warm-season grass is slowing down. This reduces competition from unwanted grasses. Typically, overseeding should be initiated two weeks prior to the first frost in high elevation areas or when soil temperatures reach about 65 to 70????? F. Gulf Coast states can overseed through November, and much of Florida can overseed through mid December.

Overseeding And Winter Lawn Pointers

Before seeding, first remove excess thatch through verticutting, slicing, spiking, or core aerifying to encourage seed and soil contact. Very close mowing and clipping removal just prior to seeding will further open the turf up. Soil coring should be done a few weeks before the seeding date. After drying, the soil should dragged back into the turf with link fence mats. This is also the optimal time to level low areas. Apply sufficient quantities to bring the surface back up to grade to provide a level playing area.

High rates of overseeding on bermudagrass can cause Poa trivialis or perennial ryegrass to remain in a seedling-like stage for weeks, possibly months, after overseeding. This turf is highly susceptible to several pathogens (Rhizoctonia, Pythium, Microdochium). Recovery from disease if often poor due to the ?EUR??,,????'??seedling-like?EUR??,,????'??? state of the turf. Therefore, it is important to use preventive, rather than curative, control on overseeded greens. Low temperatures and low light during winter months also result in slow recovery. Consider using regular preventive applications of broad spectrum fungicides on overseeded greens. Fungicide treated seed can also be planted to reduce seedling disease such as Pythium (shown here).

Seed in at least two directions. Rake seed into soil and lightly topdress for seed coverage. Next, prudent watering is essential. Apply light applications at least twice a day until seeds have germinated and a solid green cast appears. Then reduce irrigation frequency to reduce disease pressure. Once mowing is initiated, water only on an as-needed basis. Maintain your winter lawn/field as you normally would. Mow when grass reaches 1 to 2 inches height. Fertilize on a regular basis to encourage rapid growth and recuperation after heavy play. The first fertilization after establishment should be made about one week following full germination with a complete fertilizer at a nitrogen rate of 0.5 lb per 1,000 sq. ft.

Turf Facts

3 to 5: Years, a soil test is recommended before a seeding project begins if it has been longer than this period of time.

20 to 40: Holes per square foot, a good ratio for core aeration. Punching this number of holes will increase the seed-soil contact and improve germination and establishment rate.