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Overseeding fescue lawns still possible this spring
Kansas Central U.S. homeowners' hopes for a high-quality tall fescue lawn this year seemed more than reasonable in March. Now, however, some are facing months of mowing an April freeze--or May, flood-thinned yard. "To a degree, Kentucky bluegrass can repair itself. Until it's overseeded, however, tall fescue will remain more open and thus more vulnerable to weeds," said Rodney St. John, turfgrass horticulturist with Kansas State University Research and Extension. Fall is the long-recommended time to start or renovate such cool-season turfs in the High Plains. "But, if you have a disaster and want to get something started, now is okay. It's just more work," St. John said. "The only exception is if you already have put down a Step 1 pre-emergent product, such as the Scott's brand of Turf Builder with Halts Crabgrass Preventer. If so, you'll have to wait until September." Seed variety always has a big impact on end results, he said. K-State posts annually revised test results for the region's major lawn turfs at www.oznet.ksu.edu/ (search for "Turfgrasses Recommended for Kansas"). "Any of the listed turfs should still be available at local garden centers in this part of the world," St. John said. "What you want to avoid is K-31 tall fescue, which is even more readily available and fairly cheap. "I only recommend K-31 for outlying areas on multi-acre county estates, not home lawns. It grows faster than the turf fescues. It also tends to get stemmy, develop clumps and be a lighter green." Even on existing K-31, overseeding with a turf-quality fescue will achieve a better lawn, he said. One reason spring seeding is harder than fall's is that it means a battle with weeds. Spring's window of opportunity for controlling broadleaf lawn weeds (other than by hand) is already closed, St. John said. Many of the grassy annual weeds are already sprouting, too. "To control any crabgrass, foxtail and barnyard grass that hasn't emerged, however, applying the preventer siduron (Tupersan) is safe for both newly seeded and established cool-season turfs," he added. After that, the keys to success in turf seeding are always the same: 1) Achieving good seed-to-soil contacts and 2) Keeping the soil surface moist while the seed germinates. St. John said one good way to get seed-to-soil contact is: Rent and then run a hollow-tine core aerator across the lawn in one or more directions. (This also will reduce soil compaction.) Allow the soil "cores" deposited on the lawn to air-dry. Mow grass short--about 1 to 1.5 inches--to allow more sunlight to reach the seeds, as well as chop up a few of the dried cores. Seed. Then feed with a starter fertilizer, which is a high-phosphorus fertilizer such as 10-20-10 or 8-24-16. "You can spread seed and fertilizer with either a drop or rotary spreader. Just do it evenly," the turf specialist said. "Usually going over the lawn with your spreader in two or more directions will give you good, uniform distribution." For better soil-seed contact on lawns with good soil structure, he recommends: Mow grass short. Rent a verticutter or slice-seeder and go over the yard in one direction. Rake up and remove thatch and leaf debris, if necessary. Broadcast or drop the seed. Verticut in a second direction. Apply starter fertilizer. "All things being equal, if I had to choose between verticutting or aerifying, I'd verticut. I believe it gets more seeds in contact with the soil per square foot. But, aerification can be very important for our good Kansas clay soils," St. John said. With that in mind, homeowners can achieve the maximum aeration and soil-to-seed contact by core aerating, allowing the cores to dry, and then verticutting (as above), he said. "You shouldn't need to mulch the seed after planting, since the existing turf will help hold it in place," St. John said. "I don't normally recommend the traditional straw mulch anyway, because it usually contains weed seeds and limits sunlight's penetration to the turf seeds." Keeping the soil moist until the new seeds sprout can be trickier in spring than in fall, he said. "The best advice for established lawns at this time of year is to keep your lawn a little on the dry side. Water deeply and infrequently," the specialist said. "Until we get into hot, windy weather, that usually averages out to making sure the lawn gets an inch of water every seven to 14 days." But, newly sodded turf and turf seedlings need watering lightly and frequently. The aim with them is to keep the soil surface moist, but not have standing water or super-saturated soil. "Of course, the new turf won't have a super-deep root system by the time summer hits. So, you'll have to water more often than normal through the season, to make sure your seedlings and turf sod survive the heat of summer," St. John said. Overseeding when the weather is hot, dry and windy can require irrigating germinating fescue 3 to 5 minutes at a time, two to four times a day. During average spring weather, however, a light watering once a day is generally enough, if rain isn't doing the job, he said. "After the seed germinates and begins to grow, you can start to increase the amount of water you apply each time and increase the number of days between watering," St. John said. "But, continue monitoring for signs of drought stress more closely than you would in other years." Links to K-State Research and Extension turf publications and updates are at www.oznet.ksu.edu/Topic6.asp. County or district Extension offices can also provide further information and recommendations. Date: 9/21/07
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