A common question I get throughout the year is “When do I need to sow grass in my yard?” It’s a great time to talk about this because as a former Extension Specialist once said, “The best time to plant cool-season grass is September, and the next best time is next September.”
Turf type tall fescue is the primary grass used in home lawns across Tennessee. It tolerates heat, drought, and pests better than other cool-season grasses and looks better during the winter than warm-season alternatives. So for our purpose today, let’s focus on reseeding tall fescue.
Homeowners commonly want to broadcast seed on the existing lawn without removing the existing weeds and turf. However, just because it is common, that doesn’t make it the right choice. For seeds to germinate and grow, they must have good contact with the soil. This is nearly impossible if there is thick thatch and weeds.
Even if the seed does manage to contact the soil surface and germinate, this tender seedling has to compete with mature plants for sunlight, water, and nutrients. It will lose that battle more often than not. Killing the existing sod with either herbicide or tillage will greatly improve your chance of success.
If you have small trouble spots that need reseeding, you can work the ground with a hoe or tiller and then reseed. Small bare spots in lawns can be renovated without destroying existing grass or preparing the seedbed. Broadcast seed on the soil surface and then cover the seed with about an eighth of an inch of topsoil or sand.
A better option for larger areas is to use a dethatching machine that will loosen dead grass, weeds, and thatch and leave slits in the soil surface for seed to fall into. Renting one of these machines and crossing the area to be reseeded several times will increase your chances of success. After dethatching, evenly broadcast seed at a rate of 5-8 pounds per 1,000 square feet for tall fescue. Rake the seed lightly into the seedbed or cross the area again with the dethatching machine.
Another option is to rent a no-till drill. Keep in mind that some of these are designed for pasture and will plant in rows 8 inches apart which is too wide for turf. To combat this, simply cross the turf area two to four times, preferably in different directions.
With a drill, calibrate to apply ½ to 1 pound of seed (tall fescue) per 1,000 square feet per pass, or 20 to 40 pounds of seed per acre per pass. If you cross the area three times, you will be seeding from 60 to 120 pounds of seed per acre. Do not use higher seeding rates for each pass, because all the seed is placed within a narrow slit. If too many seeds germinate within the slit, the seedlings will remain very immature and have poor drought/heat tolerance and often become diseased.
Preparing a seedbed with an aerifier (coring machine) is another great method to thicken a tall fescue turf that you do not want to injure with a non-selective herbicide. An aerifier does much less damage to an existing turf than the dethatching machine. Cross the area multiple times, with the tines on the aerator going about ½ to 1 inch deep in the soil. After this minimal seedbed preparation, broadcast tall fescue seed at 250 pounds per acre. Then drag the area with a section of chain link fence, a piece of carpet, or a steel drag mat.
Mulching new plantings, watering during dry periods, and maintaining proper fertility are also critical components of reseeding. For more information on turf seeding and management, contact the University of Tennessee Extension office at 615-735-2900 or visit turf.tennessee.edu.