The greening up of warm-season grasses: What you need to know

As we move into the warmer days of spring, many of the warm-season lawns - Bermuda, centipede and zoysia - are beginning to come out of winter dormancy and green up. As soil temperatures rise in the spring, the over-wintering parts of the grass plants, such as the stolons or roots, begin to generate new leaves and roots.

The greening-up period during the spring is very critical to determine how vigorously the turf grows and how attractive it will be.

The process of the turf going from dormancy to turning green and actively growing can vary from two to six weeks, depending on the temperature and rainfall. Herbicide treatments during the green-up phase can damage lawns, especially centipede grass.

Sometimes lawn grasses are adversely affected by extremely cold temperatures and may be weakened or killed in areas, called "winterkill." Diseases, poor cultural methods or adverse weather conditions in the growing season in the previous years can make the turf more susceptible to winter kill. The best course of action is to examine how the lawn is being cared for and try to improve on it. In some, the turf will fill in these areas, or you may have to reseed or sod.

There are other factors that affect spring transition of warm-season turf grasses:

Areas of the soil that remain excessively wet or dry will be slow to green up.

Shade: Heavily shaded areas warm up slower and green up later than areas that receive more sun. Soils that are compacted cause the recovery of dormant grasses to be slower since they restrict oxygen to root systems.

Winter weeds, such as annual bluegrass and shade grasses, compete for water and nutrients. After they die out, they leave bare spots and are often replaced by summer weeds. You can apply a post-emergent herbicide to control these weeds.

Several steps can be taken before green up begins but after the danger of prolonged cold has passed to encourage turf during spring transition. Begin scalping your turf. Lower the mower blades to remove the dead leaf material from dormant grasses. Scalping will allow the soil to warm up faster and will increase the rate at which turf grasses green up. Be careful when scalping zoysia. Unlike Bermuda grass, zoysia is not as tolerant of heavy scalping. Do not remove over one-third of the leaf blade, even when dormant, since this will interfere with the greening-up process. Never burn dormant grass to remove the dead leaf blades from the previous year.

Aerating the soil helps relieves soil compaction and increase the movement of water and air into soil. If aeration is unable to be performed before green up begins, then wait until after it has completely greened up.

Consider having your soil tested. Use a small shovel or soil probe and take a 4- to 6-inch samples from several areas across your lawn. Mix the samples together in a bucket, and put a small amount of the soil in a plastic bag, and bring it to the Extension office. For $8, the sample will be sent to the soil testing lab at the University of Georgia to be tested for pH, and several of the major nutrients. You will get the results back in seven to 14 days.

Avoid fertilization applications of the lawn until it has completely greened up. Early fertilization may make the turf more susceptible to a late freeze and the damage it could cause. Apply a complete fertilizer such as 12-4-8, 10-10-10, or for centipede, 15-0-15 at the rate of one pound nitrogen per 1,000 square feet when about most of the turf is green.

Just remember the do's and dont's for lawns during the spring green up. A little planning along with proper cultural practices, your warm season lawn can be healthy, attractive and the envy of your neighborhood.

Timothy Daly, MS is an agricultural and natural resource agent with the Gwinnett County Extension Service. He can be reached at 678-377-4010 or timothy.daly@gwinnettcounty.com.