Cool-Season Turf for Warm Climates

Recent improvements in heat and drought tolerance of cool-season turfgrass varieties create viable year-round alternatives and overseeding options for residential lawns.

New grasses for all-year appeal

For the past several years, turf-type tall fescues have been the go-to grass for anyone desiring a green lawn year-round. Recent introductions showing better heat tolerance include Arid, Falcon, Jaguar 3, Mustang, Apache and Rebel II.

Tall fescue requires at least 4 hours of direct sunlight for success. It is not as resilient to traffic as the more traditional warm-season grasses, such as bermuda and St. Augustine, and in the summer, needs an inch of water every 3 days.

Hybrid bluegrasses like Reveille and Thermal Blue have also made great strides where heat and drought are concerned. Light requirements for these bluegrasses are full sun to partial shade, or at least 4 hours of direct sunlight. Hybrid bluegrasses prefer 1 inch of water every 5 to 7 days.

Overseeding for winter

Usually, specific varieties are not a concern when overseeding with either perennial or annual ryegrass. However, two annual ryegrass selections, Pantera and Excella, have a deeper green color, similar to perennial ryegrass. This characteristic makes these more attractive to use for overseeding, because they will not last as long into the spring as perennial ryegrasses do.

Converting a warm-season lawn to a cool-season turf

1. Treat existing lawn with a glyphosate product. Wait 10-14 days until brown. Continue to irrigate 24-48 hours after treating. Bermudagrass is especially persistent and 2-3 follow-ups may be needed to ensure lawn is dead. Plan to start glyphosate treatments in late August. That way, bed preparation and seeding can take place by early October.
2. When lawn has died, lower mower setting in stages until the height of the stubble is no more than 1/2 inch.
3. Lightly till or use a power rake or dethatching machine to penetrate the crust of the soil.
4. Level and smooth the soil by raking.
5. Fertilize prior to seeding at half the recommended rate.
6. Sow seed evenly; tall fescue at 6-8 lbs. per 1,000 sq. ft. and hybrid bluegrasses at 3 lbs. per 1,000 sq. ft.
7. Drag the backside of a rake over the seeded area to ensure good seed-to-soil contact.
8. Water to keep soil surface moist, but not overly wet, until germination occurs. With automatic sprinkler systems, this may require 2 to 3 different start times during the day for short durations (3-5 min. for spray heads, 10-15 min. for rotors).
9. When seed has germinated, gradually decrease frequency of watering while increasing watering time until the lawn reaches its normal watering interval based on variety requirements.
10. Mow the first time on the highest setting when height reaches 3-4 inches, subsequent cuttings at recommended heights for individual varieties.
11. Fertilize after third mowing at ½ the recommended rate.

About the author: Mike Sutton is a horticulture graduate of Purdue University with more than 20 years’ experience with turfgrasses in Texas.

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Posted by Neil Sperry
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