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Help warm-season turfgrasses green-up

By Gil Landry and Clint Waltz
University of Georgia

Warm-season turfgrasses such as Bermuda, centipede, zoysia and St. Augustine suffer some common problems with springtime green-up. Here are the ones we see most often.

Mowing height is the most common problem as these grasses go from dormancy to active growth. Scalping is more common in zoysia grasses, especially in the denser-growth cultivars like Emerald.

Zoysia grasses don’t tolerate scalping as Bermuda will. As a rule, zoysia will be set back anytime it’s cut low enough that you can see the black mold under the leaf canopy. This is generally below the node of the growing leaves. It can occur at any mowing height from as low as 0.5 inches to more than 3 inches.

Regardless of the grass species and normal mowing height, taking the grass down below the node will set it back. Generally, the higher the mowing height, the more this is a problem.

Ideally, maintain Bermuda grass and centipede between 1 and 2 inches, zoysia from 0.5 to 2 inches and St. Augustine from 2 to 3 inches.

Mowing frequency is just as important as mowing height. If you remove more than one-third of the leaf height at a single mowing, the grass will be stressed.

Fertility requirements differ with each grass. Consult your local University of Georgia Cooperative Extension agent or visit www.GeorgiaTurf.com for fertility recommendations.

No matter what the species, though, fertilizing too early in the season, before soils are warm enough to support continual growth, can accelerate green-up but cause detrimental long-term effects.

Fertilizing these grasses in late-winter or early spring can cause them to break dormancy. Then when the inevitable late-season cold snap hits, they’ve used their stored food reserves. They have no energy to withstand environmental extremes. To avoid this, don’t fertilize until the soil reaches 65 degrees.

Thatch, as lawns get older, becomes more problematic, particularly if the turf has been mowed above its recommended height ranges. Increased thatch slows down the turf’s spring transition. It makes it more susceptible to disease, too.

Water - either too much or too little or even a combination of the two - can cause problems for grasses, especially zoysia.

Diseases can strike during spring green-up. The most common is Rhizoctonia large patch, which appears as large areas of blighted grass.

This disease is most active when night temperatures are between 50 and 60 degrees. When conditions are right, it’s common for the disease to become active first in the fall and then again in the spring.

You can see its typical “halo” when the disease is active. Fall and spring fungicide applications can control it. Consult your local UGA Extension agent for proper fungicides and rates.

(Clint Waltz is a Cooperative Extension turf specialist with the University of Georgia College of Agricultural and Environmental Sciences.)

(Gil Landry is a Cooperative Extension turf scientist with the University of Georgia College of Agricultural and Environmental Sciences.)

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