With summer winding down — nights are getting longer and days getting cooler — September is a perfect time to rejuvenate tall fescue lawns. Aerating and overseeding now in the fall will make your lawn stronger and better able to resist pests and weed encroachment for next season.
Here are a few points to remember when aerating and overseeding for a lawn rejuvenation this fall:
- The aerator you use makes a difference. A heavier, more powerful (> 5 HP) aerator will be more forceful and more effective in creating deeper cores. Ideally, you should be able to aerify to a soil depth of at least 3-4”. Equipment rental stores often have suitable aerating machines available. Remember not to go over the lawn too fast and allow the machine to just “bump” along. Travelling slowly and ensuring the area isn’t too dry will help encourage quality cores to be pulled from the soil.
- If you have substantial areas of dead grass or crabgrass weeds, it is probably more effective to remove the dead grass leaves with a hard rake, a “power rake”, or a de-thatcher. The turf seed will need to have good soil contact in order to germinate and grow to provide better coverage. By seeding into an area with a lot of dead debris, the seed may germinate and then dry out – or not “take” at all.
- Select quality “turf-type tall fescue” seed. The University of Maryland publishes a list of Maryland-adapted turfgrass cultivars in publication TT-77. In my experience, local garden centers tend to be more likely to stock better adapted varieties, or you can find these varieties at some professional dealers that also sell to homeowners. These varieties may be more expensive, but they tend to be worth the investment since they exhibit better quality, density, disease tolerance, etc.
- Seeding rate is important. Use a drop spreader or rotary spreader to spread the seed evenly over the area to be rejuvenated. For renovated lawns, aim for 5-7 lbs. of seed per 1000 sq. ft.; for rejuvenation of existing lawns, aim for 3-4 lbs. per 1000 sq. ft.
During rejuvenation is a good time for fall fertilization as well. The University of Maryland Extension recommendation for tall fescue lawns is to apply 0.9 lb. nitrogen/1000 sq. ft. Remember, Maryland fertilizer laws don’t allow you to add phosphorous (i.e. the middle number on a bag of fertilizer should be “zero”) unless you are doing a complete lawn renovation or have done a soil test that indicates phosphorus is needed.
By Geoff Rinehart, Lecturer, Turfgrass Management, Institute of Applied Agriculture, University of Maryland
My grass has a lot of weeds right now. Should I spray my lawn with a weedkiller, like Roundup before I fertilize for the Fall.
Barbara, take a look at this page to identify the weeds you have and the best options to control them. https://extension.umd.edu/hgic/lawns/lawn-weed-identification
Roundup will kill all of the plants, including your existing turfgrass. You could do that if you have 50% or more weeds and want to do a complete lawn renovation. Then re-seed or cover with sod. Take a look at our comprehensive fact sheet on lawn establishment and renovation. https://extension.umd.edu/sites/extension.umd.edu/files/_images/programs/hgic/Publications/HG102%20Lawn%20Establishment%20Renovation%20Overseeding-2017.pdf
Great article! I plan to rejuvenate my lawn this weekend. Should I move the grass low to help seed-to-soil contact?
Mow the lawn about 1 inch in height. Use a steel rake to remove clippings and to scratch the soil, or rent a core aerator, vertical mower, or slit seeder to make the job easier. This helps to improve seed-to-soil contact.