by Grady Miller, Professor and Extension Specialist
Fall is the best time for renovation and seeding of cool-season lawns. Temperatures are currently above normal for early September, but long range forecast predict they will begin to moderate. Also, much of the state recently had some rainfall making aerification a bit easier in previously dry soils.
Remember that spring-established tall fescue is more susceptible to drought, heat, fungal diseases, and weed encroachment. With normal summer weather patterns, spring seeding is not likely to result in a year-long stand of healthy tall fescue. So do not delay, seed in the fall!
Young seedlings normally emerge and grow best when air temperatures are between 70 and 80 degrees. Soil temperatures need to be greater than 60 degrees for good germination. So, it is generally better to go a bit early than seeding late. If tall fescue is seeded in under less than ideal conditions (too cool or no soil moisture), you may experience a thin turf stand going into the winter. So try to get your seed out in September. If you must wait until October there is an increased likelihood of slow/low germination.
It is best to choose cultivars from the TurfFiles website. There is a list of the 2016 Top Performing tall fescue and Kentucky bluegrass cultivars: 2016 Top Performing Tall Fescue and Kentucky Bluegrass Cultivars for North Carolina. For a larger list of good performing cultivars, the 2014 lists are still a good resource: 2014 Recommended Kentucky Bluegrass Cultivars for North Carolina and 2014 Recommended Tall Fescue Cultivars for North Carolina.
If you buy a tall fescue blend, try to find one with at least one of the cultivars from the list of recommended cultivars. These grasses were chosen because they produce a high quality turf in North Carolina and have been shown to be less susceptible to brown patch. Some like to mix in a little Kentucky bluegrass (darker color and finer texture) or fine fescue (for shady areas). Do NOT add ryegrass to the mix. A typical tall fescue seeding rate is 5 to 6 pounds of seed per 1000 square feet. Germination will normally be in 7 to 14 days with soil moisture and suitable soil temperatures.
Before seeding core aerification is recommended to reduce compacted areas. Getting good soil to seed contact is paramount to maximize available soil moisture. The core aerification holes will capture seed and hold moisture so the tall fescue seedlings often come up as a tuft of turf from the aerification holes.
Follow normal tall fescue or Kentucky bluegrass fertilization practices as outlined in Carolina Lawns available on the www.turffiles.ncsu.edu website. The suggested yearly nitrogen application is about 1.0 pound of nitrogen fertilizer per 1000 square at seeding. Include phosphorus and potassium fertilizers if soil tests indicate there is a need. In the absence of a soil test, a 16-4-8 or similar N-P-K ratio fertilizer may be used this spring. Before additional fertilizer or lime is added, conduct a soil test (http://www.ncagr.com/agronomi/sthome.htm).
To apply 1 pound of nitrogen per 1,000 square feet: Divide 100 by the first number on the fertilizer bag to determine the amount of product to be used per 1,000 square feet. Example: Using a 16-4-8 fertilizer, 100 divided by 16 equals 6.25, therefore, 6.25 pounds of fertilizer per 1,000 square feet will deliver 1 pound of nitrogen.
If irrigation is available, set your controller within current water restrictions for your area. Irrigate early in the morning to reduce water loss due to evaporation. In the fall, ¼ to ½ inch water per week of water (via rainfall or irrigation) is generally sufficient to meet the turf’s water needs.
Since seeds and seedlings may be damaged by some herbicide applications, fall seeded cool-season grasses should not have any herbicides applied until it is extensively tillered.
It is very important that tall fescue be maintained at the proper mowing height to allow it to mature before winter and to minimize weed incidence. Studies have shown that a 3½ mowing height provides the best growth condition while minimizing disease incidence and weed encroachment. A 3 to 3.5 inch mowing height is also a good height for tall fescue + Kentucky bluegrass.
Note that warm-season grasses such as bermudagrass, zoysiagrass, centipedegrass, and St. Augustinegrass can be sodded in the fall, but it is generally not recommended due to the increased chance of winterkill. Warm-season grasses should not be seeded in the fall as there is inadequate time for maturity before the first expected frost.