Released: February 03, 2006

Still Time to Overseed Fescue, Bluegrass Lawns

LEAVENWORTH, Kan. – Many tall fescue and Kentucky bluegrass lawns have bare spots or thin areas that aren’t up to par. Some develop such flaws every year.

September is the ideal month for overseeding. Even so, lawn owners who didn’t get the work done last fall still have some opportunities, said Leon Stites, natural resources agent for Kansas State University Research and Extension, Leavenworth County.

“You can try overseeding your dormant lawn. The month of February is a pretty good time for that,” Stites said. “Or, you can spring seed in March or early April.”

Either approach will make crabgrass control for the year more difficult, he warned.

Dormant overseeding offers three options:

* Wait for a light snowfall – one that leaves the lawn’s bare or thin spots still visible – and then spread seed on top of problem areas. As the snow melts, the seed will settle and achieve good contact, because the soil surface will be damp.

* Overseed when soil is moist, plus going through a wintertime freeze-thaw cycle. The freeze-thaw combination forms small pockets that are like bubbles of air on wet, bare soil. The pockets catch seed and eventually collapse, ensuring the seed gets covered just under the soil surface.

* For larger areas where the soil is dry and NOT frozen, rent and use a verticutter. Then seed.

“As the soil warms up in spring, the seed applied while the lawn is dormant will germinate and become established,” Stites said. “If this spring is as damp and cool as usual, you won’t have to provide any further care.”

The problem with overseeding in March or early April is that spring can bring heavy rains. Pounding moisture either piles up grass seed against the nearest rise or washes it away.

“You can verticut the ground first to help keep the seed where you put it. But, a heavy rain may still cause washing,” Stites said. “The soil will be springtime cool, too, which means the time between seeding and germination will be longer than it is in September. So, you’ll have more time for rains.”

K-State recommends applying most crabgrass controls only after new grass plants have grown enough to require mowing two to three times.

“Crabgrass preventers don’t discriminate between turf and crabgrass,” Stites explained. “When we apply these products in spring, we rely on having fescue or bluegrass roots that extend below the new herbicide barrier we’re putting down.”

The two exceptions to the rule are siduron (Tupersan) and dithiopyr (Dimension).

“Tupersan is actually okay to use on newly-seeded turf. But, it’s a short-term control that is somewhat less effective than other pre-emergence herbicides. You generally end up needing to apply it again about six weeks later,” Stites said.

Dimension is not safe for turf seeds or seedlings. Still, for lawns planted by the end of March, Dimension applied in early May can safely and effectively control both crabgrass seeds and seedlings. And, because Dimension is a long-term control, it won’t require a second application.

“The only problem with Dimension is that it’s usually sold in combination with a high-nitrogen fertilizer,” Stites said. “We suggest keeping the nitrogen level low if you want to fertilize fescue or bluegrass in spring. If you don’t, the result will be lush top growth.

“With a Dimension-fertilizer mix you won’t have a crabgrass problem. But, you could have a lot of watering to do until the weather cools off next fall, just to keep that lush turf growth alive.”

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K-State Research and Extension is a short name for the Kansas State University Agricultural Experiment Station and Cooperative Extension Service, a program designed to generate and distribute useful knowledge for the well-being of Kansans. Supported by county, state, federal and private funds, the program has county Extension offices, experiment fields, area Extension offices and regional research centers statewide. Its headquarters is on the K-State campus, Manhattan.

Story by:
Kathleen Ward
kward@oznet.ksu.edu
K-State Research& Extension News