Replenish Your Lawn With More Lawn

Published: September 13, 2019

Author's Note: It's crucial to know if you have (or want to have) a warm-season or cool-season type turfgrass species in your lawn. A simple question to ask is "Did my lawn turn completely tan or brown last winter and not green up until spring?" If it turned brown, the lawn is a warm-season turfgrass such as zoysiagrass or bermudagrass. In most cases, these two species are sodded, sprigged, or plugged and are not seeded. If your lawn didn't turn completely brown over the winter, it is a cool-season turfgrass, such as tall fescue, Kentucky bluegrass or tall fescue mixed with Kentucky bluegrass. This article is targeted at cool-season turfgrasses, which make up approximately 85-90% of lawns in Missouri.

Summers in Missouri are stressful on many plants and most lawns in Missouri, but fall is the time to get cool-season lawns back on track. The photoperiod (aka daylength) is shorter, temperatures are cooler, and turfgrass growth potential increases considerably. Giving the grass some food in fertilization is an obvious choice, and in most situations at least one pound of nitrogen, and up to two pounds N per 1,000 square feet in younger lawns, is recommended during the fall.

Fall overseeding isn't as obvious or discussed as often, but should be considered as a regular practice on Missouri lawns. The key to a high quality, desirable lawn is uniformity which follows a simple equation: uniformity = plant density = number of plants. We want a high number of our turfgrass plants to cover bare areas and outcompete troublesome weeds. Continuous seeding makes most weeds (think dandelions) good at their job in invading our yards… so if the weeds are doing it why don't we?

Don't know the size of your lawn? Then you shouldn't be spreading anything on it. Stop here and visit the lawn fertilizer applicator for information on how to determine your lawn area and properly calculate the amount of nitrogen fertilizer to apply. Knowing the size of the lawn will also let you calculate the proper amount of seed to buy.

Choosing the Right Turfgrass Seed & Planting It at the Right Time

Far and away, tall fescue is the most appropriate and popular species for lawn use in Missouri. The turf-type tall fescue cultivars are more tolerant of heat, drought, diseases, and insect damage than other cool-season species. Tall fescue is tolerant to moderately shaded environments. Hard, sheep, creeping red or Chewing's fescue may also be appropriate as part of a mix for use in heavily shaded areas. These species, however, have a narrower leaf blade, are not as heat or drought tolerant, and will require more frequent irrigation during a dry summer to survive.

Other species commonly sold in Missouri include Kentucky bluegrass and perennial ryegrass. Kentucky bluegrass has an advantage over tall fescue in that it spreads via rhizomes and can recover more readily into damaged areas (be aware that some rhizomatous tall fescues are becoming available). For this reason, it is heavily utilized on sports fields. However, it is more prone to diseases, heat and drought stress than tall fescue and requires more irrigation and maintenance. Therefore, by itself Kentucky bluegrass may only be suited for northern Missouri locations, but a low percentage of Kentucky bluegrass with predominantly tall fescue can be a good seed mixture. Perennial ryegrass is the quickest germinating grass (~ 7 days after seeding) and will provide immediate groundcover. This may be rewarding at first, but ryegrass is also the least tolerant to environmental stresses, and will not survive a normal Missouri summer unless intensely managed. Annual ryegrass is utilized as a cover crop, but is not suitable for use as a turfgrass in Missouri.

Timing of your lawn seeding is as important as turfgrass selection. Spring, when the snow melts and flowers bloom, is baked into our psyche as the best time to get out and plant our gardens. Seeding a lawn in April or May, however, is often a losing proposition. The summer stress period is ahead, and young, spring seedlings are mere cubs cast into an environment full of hyenas. Fall seeding allows seedlings to develop over a full fall and subsequent spring into a lion that can deal with summer heat, drought, and disease. So now is the best time to seed, build density and uniformity in your lawn, and turn it into the beast it needs to be.

How to Overseed Your Lawn

In most cases, the lawn has at least some desirable grass species left in it, so there is no need to start all over and establish from the beginning. Therefore, this is considered overseeding or renovating a lawn and the purpose as stated before is to get more players on the team. Follow the steps below for best success.

1. Control existing vegetation or weeds if necessary. Pay attention, however, if using herbicides. Selective herbicides, such as 2,4-D and dicamba, will kill broadleaf weeds and not the lawn, but often have a 3-4 week reseeding restriction after application. Spot sprays of non-selective herbicides such as glyphosate will have shorter 3-5 day reseeding intervals. Read the label thoroughly and wear gloves and other personal protective gear when applying any pesticide.
   
2. Buy your seed. Again, the size of the lawn area must be calculated first. A tall fescue overseeding rate of 3-4 lbs of pure live seed per 1000 square feet is recommended. Conversely on bare soil an establishment rate is 7 lbs of pure live seed per 1000 square feet is recommended. Pure live seed means that the germination rate of the seed needs to be taken into account. Since most germination rates are 85% approximately 3.5-4.5 lbs of purchased seed per 1,000 square feet will be needed. As an example, 28-36 lbs of seed would need to be applied to an average 8,000 square foot lawn.
   
3. Set your mower as low as possible, and scalp the existing vegetation. This will be the only time ever this will be recommended, so immediately set your blade height back to as high as possible, which should result in a 3.5-4" mowing height.


Mow low, then power rake or aerify.

4. Prepare the soil surface by either core aerification or a power rake/verticutter. These units can be rented as various locations in most cities. If using a power rake/verticutter, make sure the blades are set low enough that you observe a small amount of soil being pulled up along with the plant debris. The practice does look a bit like a bomb going off in your yard, so be prepared to answer some questions.


Clear debris.

5. Rake up and remove loosened thatch and debris.
6. Add fertilizer. Add lime if needed. A soil test should guide the requirements for lime, phosphorous and potassium. Most starter fertilizers will have nitrogen, phosphorous and potassium in them (i.e. 10-10-10).
7. Make another light pass with power rake/verticutter or core aerifier to create channels for seed.


Seed and Fertilize.

8. Cut the overall seed amount in half, and spread evenly in two directions. This will prevent skips and encourage uniformity.
9. Use a blower on impervious surfaces like roads, sidewalks and driveways to blow fertilizer and seed back onto the lawn. Use all of your resources on the lawn and prevent pollution.
10. Lightly rake seed into the soil surface.
11. Water frequently until the seed establishes. A good adage is to water until the soil gets dark, but doesn't glisten. Once established, water less frequently.

How often to overseed?

This depends completely on the goal and tolerance level, but some form of overseeding along with aerification should be considered every three to five years. Following all of the above steps to the letter may be viewed as extreme and exceptionally difficult, but in no way should they discourage the ambition of picking up a bag of seed and putting it down in the fall to go with fertilization and aerification. To steal an adage from Dr. Trey Rogers at Michigan State University "Grass dies, and the sooner you learn that, the better turf managers you will become." Lawns shouldn't be viewed as an everlasting resource that once planted are magically going to persist in a dense mat forever. No plant species in Missouri can live up to that expectation. Consider replenishing your lawn with more lawn by overseeding regularly in the fall.