Grasses are either “cool season” or “warm season”. Cool season grasses (such as Turf Type Tall Fescue, Rye grass, and Kentucky Blue Grass) thrive in spring and fall, and struggle in the heat of summer (often going dormant / turning yellow). Warm season grasses (such as St. Augustine, Zoysia, Bermuda) thrive in the heat of summer, and struggle when the weather cools. Hopefully this description helps you to know whether your yard has cool or warm season grass. I am located in zone 7A and have Turf Type Tall Fescue grass (TTTF for short), so this post focuses on caring for TTTF in the early fall. I will not discuss care of warm season grasses as I have no experience with them.

Fall is the optimal time to repair summer’s damage to cool season grass. Timing is important – start too early, and summer heat will ruin your efforts. Start too late, and your new grass seedlings won’t be strong enough to survive the first frost (normally late October in my area).

When developing your fall lawncare plan, you must first assess the condition of your existing grass. How much grass do you have versus weeds? In general, if your yard has 30% or more grass and 70% weeds, you can kill the weeds then perform the steps described below to fill in the bare spots. If your yard is almost all weeds, you can perform a “lawn renovation” (indescriminately killing existing weeds and grass then planting new seed). Lawn renovation is obviously more radical and more scary (if you fail you have no grass), so I will discuss it in a separate post.

Below are the major steps I perform each fall. For my location in Zone 7A, these steps occur from mid-August to mid-September.

Fall Lawn Repair steps are:

• Purchase supplies as needed
• Kill weeds several weeks before planting seed
• Aerate and dethatch
• Overseed. Note that overseeding is not required for Kentucky Blue Grass as KBG spreads naturally and will over time fill in gaps in your lawn. TTTF and rye are “clumping” grasses and do not spread. You therefore need to plant new TTTF or rye seed in areas that are thin or bare dirt; otherwise, weeds will take over the empty space).
• Water and apply starter fertilizer (seed must be kept moist until it germinates)
• Mow two weeks after seed germinates
• Apply winterizer fertilizer

I plan to write separate detailed posts on each step. Below is an overview of each step.

Steps to Green Grass

Purchase Supplies

You will need weedkiller, fresh grass seed, and starter fertilizer, and several tools . These items can be in short supply once Fall Lawn Repair Season starts so best to purchase in August to avoid the September rush. You can shop at a Big Box store (such as Home Depot and Lowes). You can also purchase online (I have bought seed and fertilizer from both sites below):

• GCI Turf Academy
• Yardmastery

Kill Weeds

Weeds make your lawn look wild and uncared for. Weeds also steal water that your grass needs to stay healthy. Weeds also fight grass for survival, and often win unless your grass is very healthy. But you can conquer weeds! When I first became serious about lawncare, I struggled with weeds for about a year. But once my grass thickened, it was able to prevent most weeds from growing.

If you have a few weeds, feel free to dig them out. But, be sure to dig out the roots (and I mean ALL of the roots), or the weeds will grow back from the roots. For a guaranteed kill, spray a herbicide (aka weedkiller) on each weed.

If your yard is covered with weeds (>50%), you should do a “broadcast spray”. This means spraying herbicide over the entire yard. If you have a few weeds (<50%), you can spot spray, meaning that you only spray the weeds, not the entire lawn. Spot spraying is definitely preferable, as it saves money and is better for the environment. When I first got serious about lawncare, I did two broadcast sprays to get my weeds under control. Since then, I only spot spray my weeds. Of course, as a retired engineer, I have time to search and destroy weeds in my yard. And enjoy watching them wither away after I spray them.

I’ll write a separate post on common weeds and the chemicals that will kill them (there isn’t a single chemical that will kill all weeds without also killing your grass – you knew this wouldn’t be easy, right?). If you can’t wait for that post, try Spectracide Weed Stop for Lawns which targets many common weeds.

If you plan to overseed (discussed below), it is best to kill your weeds several weeks before you overseed.

DO NOT’s for killing weeds

• DO NOT apply weedkiller to freshly germinated grass seed, as the weedkiller can damage the young seedlings. I won’t apply any herbicides to my lawn until late October so that my new grass seedlings have time to establish.
• DO NOT apply weedkiller when air temperature at application time is above 85F. In summer apply weedkiller early in the morning when temps are in the 70s to low 80s.
• DO NOT apply weedkiller when rain is expected within six hours. It takes several hours for newly applied herbicide to become “rainfast” (meaning it has dried or been absorbed by the plant). Each herbicide’s label states a rainfast time for that chemical. Six hours should cover almost all weedkillers.

Dethatch

Dethatching is the process of removing dead grass from your yard and thus exposing the dirt underneath. Seed germinates from contact with dirt, so that dead grass covering the dirt needs to be removed.

If you don’t mow regularly (I’ll write a separate post on mowing), you will have a lot of dead grass between your grass plants. This is because small cuttings decompose more quickly than large cuttings.

Thatch is bad for several reasons:

• Prevents water from reaching the soil
• Can kill the grass if it is too thick (especially if you leave clumps of cut grass on your lawn – clumps occur when you don’t cut the grass often enough or when you cut the grass when wet)
• Insects hide in the thatch
• Seed you put down will lay on thatch rather than soil, and thus won’t germinate well. Seed is expensive – you don’t want to waste it.

So how do you dethatch? A few choices:

• Use a dethatching rake to remove the dead grass from your yard. This is strenuous exercise if you have a large yard.
• Buy (or rent) a dethatcher. I have a battery powered Ryobi dethatcher that works well (I hate tripping over cords).
• Use a high-powered backpack blower. My Stihl BR700 backblower is strong enough to blow most of the dead grass out of the lawn when pointed downwards. I use my BR700 to clean up the thatch pulled up by the Ryobi, and also to get any the Ryobi missed.
• Pay someone to dethatch your yard for you

Note that dethatching stresses your grass, so don’t do it when it is too hot (such as in the heat of July or August) because your grass is already stressed from the heat.

Before dethatching (or aerating), cut your grass lower than usual. For instance, I normally cut my TTTF at 3.5" or 4.0" during the summer, but I cut it down to 2.5" before aerating. Grass cut at a lower height helps consumer-grade dethatchers to not bog down.

Aerate

Aeration breaks up the hard, compacted soil in your yard, allowing water and air to penetrate. This softens the soil so that grass roots can more easily spread. If you were planting a flower, you would use soft, loose soil. Aerating attempts to soften and loosen the soil in your yard to create a good planting bed for your grass seed.

An aerating machine “pulls cores” of dirt from your yard, and discards them on top of the grass. They eventually melt back into the yard. Proper aeration requires a heavy machine that can be rented from a Big Box store. Retired Engineer pays someone to aerate the yard (they push around the big heavy machine so I don’t have to).

An alternative to aerating is to use a Garden Weasel to break up the dirt in bare spots before seeding. I plan to do this on bare spots in my yard in 2024.

If you don’t know when your yard was last aerated, then it needs to be aerated!

I plan to skip aerating my lawn in 2024 as my dirt is already fairly soft. Instead, I’ll use a garden weasel to break up the dirt in bare spots. I will probably pay someone to aerate my yard in 2025.

Overseed existing grass

We have finally arrived at the the easy part – overseeding!

TTTF and rye grass do not spread naturally so need to be overseeded to thicken a lawn or to fill bare spots.

KBG is a “spreading” grass so will slowly fill in bare spots and thus overseeding is not needed. You can speed KBG spreading by using plugs.

Buy grass seed and spread it on your yard using either a drop spreader or a broadcast spreader (drop spreaders drop seed precisely underneath the spreader, while broadcaster spreaders toss the seed several feet on either side of the spreader and make quick work of overseeing a large yard). Drop spreaders tend to be better for smaller yards or yards with lots of obstructions (trees, flower beds, curves, etc). Broadcast spreaders are good for large open areas. That said, my yard has lots of obstructions and I still use a broadcast spreader.

A few considerations when buying a grass seed:

• If you know what kind of grass you have (TTTF, Rye, KBG) you should purchase the same kind of seed
• Check the expiration date on seed you buy at a Big Box store – newer seed will have a higher germination rate (germination rate is the percentage of seeds that sprout).
• Buy grass seed which does not contain weed seeds. Surprisingly, inexpensive grass seed contains a percentage of weed seed as well. The seed bag will have a tag which lists the ingredients, including the percentage of weed seed. Try to buy seed that has 0% weeds (you don’t want to plant new weeds!). Tangent – When you look at that tag, you may be surprised to find that your bag of TTTF actually consists of several different varieties of TTTF blended together. This blend of different varieties improves resistance to disease.

When should you spread your grass seed? TTTF and Rye grass seeds germinate in about a week. KBG germinates in 21 days!

Here are a few tips for seeding TTTF:

• Don’t spread seed if temperatures in the next week are expected to be greater than 85F. Temperatures that are too high can burn or kill newly sprouted seedlings.
• Don’t overseed if torrential rains are expected. Light rains are very helpful for keeping seeds moist, but heavy rain can wash away seed (especially from bare spots). Note also that if your yard has hills, heavy rain can wash the seed down the hills. This can be mitigated by putting hay or other material on top of the seed.
• In zone 7A, I typically overseed in the middle of September. Some years I have seeded in late September (this was before I retired when someone else owned my time) – I have had less success with overseeding at the end of September, as the new seedlings don’t have enough time to get established before the first frost.
• Keep fallen leaves off grass seed and new grass, as they will block the sunlight from the seed / new grass.

Water and Fertilize

Seeds require water and direct contact with soil to germinate. We prepared the soil by dethatching and aerating (or using a garden weasel). It is now critical to keep the soil moist until the newly planted seeds germinate. When overseeding, I run my built-in sprinklers in the morning, early afternoon, and late afternoon for approximately 10 minutes each time. I do this for approximately two weeks (most TTTF/rye seeds germinate within a week, but there are always a few slacker seeds that take longer). I then reduce watering to once per day for a week, then once every other day for a week, then two days per week. If you don’t have sprinklers, try to seed when the weather forecast shows several rainy days. Note that fall dew helps keep seed moist. I intend to experiment this year to see whether I can replace my early morning sprinkler run with dew – enjoying my retirement!

In bare spots (and thin spots like underneath a tree), I put down peat moss on top of the seeds. Peat moss holds water, and turns dark brown when wet. If I see that my peat moss is light brown rather than dark brown, I need to water it!

Apply “Starter Fertilizer” immediately after seeding. I do this no later than the day after I seed. I have had TTTF germinate within four days, so don’t procrastinate with applying Starter Fertilizer – you need to get the fertilizer down before the seeds start to germinate.

What is Starter Fertilizer? It is fertilizer that is formulated to help seedlings establish and grow. All fertilizers are described by 3 numbers, such as “20-20-20”, or “24-0-8”. The first number is the percentage of Nitrogen, the second is the percentage of Phosphorus, and the third is the percentage of Potassium. These are the three major elements that contribute to plant growth and health. Starter fertilizers have roughly the same amount of each element. So 20-20-20 is considered a Starter Fertilizer, while 24-0-8 is not. A handy way to summarize the three numbers is “up, down, all around”. In other words, Nitrogen helps a plant grow above ground, phosphorus helps establish a good root system, and potassium is good for overall plant health. You want all of these for your new seedlings, which is why the percentages of each are typically identical in a Starter Fert. Tangent – have you noticed that the numbers do not add up to 100%? The remaining fertilizer content may be “micronutrients” such as iron or calcium, and also filler (i.e. stuff that makes the fertilizer easier to spread but doesn’t benefit the grass).

Mowing after overseeding

Do not cut your grass for 2 - 3 weeks after overseeding. In fact, try to avoid walking on the grass once the seedlings have germinated. This will allow the seedlings to get established before being stressed by you stepping on them or pushing a heavy lawnmower over them.

Do not be afraid to cut your seedlings once they are long enough to be cut (in my case 2.5 to 3 inches tall). Mowing is good for grass – it stimulates growth. You should cut your seedlings several times before they sleep for the winter.

Winter Fertilizer

The above steps describe my early fall lawn care routine. My goal is to thicken and renew my existing grass by adding new grass, and to fill in bare / dead spots.

My final fall lawn care step for the fall season is to “put the grass to sleep” with a late fall feeding. In zone 7A, I typically do this feeding in late October or early November (about six weeks after overseeding). This feeding helps prepare the grass for the stress of winter, and in my case, often keeps my grass green until February when it finally goes dormant for the winter (waking up again in late March). A fertilizer with high nitrogen content (such as 24-0-8) is appropriate for the winterizer feeding.

Fall Lawn Care Calendar

The following calendar summarizes the steps listed above:

Date	Action
mid-August	Kill weeds (when temp < 85F)
Sept 1	Lower grass cutting height
Sept 7	Aerate / Dethatch
Sept 15	Apply seed
	Apply starter fertilizer
	Water to keep seed moist
Sept 30	Reduce watering as seed germinates
Early October	Cut grass
Late October	OK to apply weedkiller
	Apply winterizer fertilizer

Case Studies

Case 1 – Bare Spots

The photo above shows clumps of grass surrounded by bare spots. The bare spots are filled with dead grass. This was probably caused by lack of water during a summer drought. The grass appears to be Turf Type Tall Fescue. My recommendation for this situation is to remove the dead grass with a dethatch rake or garden weasel, then overseed with TTTF. The grass will look consistently thick and green by spring.

Case 2 – Salad bowl of mixed greens

This lawn has a lot of good TTTF grass, but also a lot of weeds. Yellow dandelions and other broadleaf weeds are visible. Grass has dead spots due to lack of water during summer drought, and these are filled with dead grass (and broadleaf weeds). Patches of nutsedge are visible (lime green color versus the dark green TTTF) – see left middle as well as right upper areas of photo. Click the photo to zoom.

To repair this lawn, first spray herbicide(s) to kill broadleaf weeds and nutsedge. Once the weeds are gone, remove the dead grass by dethatching. Then break up the soil in the bare spots using a Garden Weasel. Overseed, and water / fertilize as described above. Grass will be thick, lush and dark green by spring.

Conclusion

The steps above will help you have a nice lawn. They sound like a lot of work, but can be done on a few early fall weekends.

There is a tremendous sense of accomplishment that comes from turning a weed-filled mess into the best lawn on your street. Every time you come home after a frustating work day, you will see your beautiful green grass and feel a tremendous sense of satisfaction! As for this Retired Engineer, even though no longer coming home from work frustrated every day, I still love seeing my beautiful green grass!

For the Sticklers

• What I called “thatch” above is really dead grass. A more precise definition of thatch from GardenSeeker is “Lawn thatch is a fibrous layer of predominantly dead and some living grass roots, stems and runners. This layer lies between leaves of the grass plant above the surface, and the root system below. It is broken down and decomposed naturally by microbes, bacteria and fungi in the soil. In an ideal world, it would break down at the same rate at which new grass grows and therefore, it should never cause a problem. However, thatch contains a chemical compound called Lignin which is slow to break down. Unless conditions are perfect, which they rarely are, new grass often grows more quickly than the dead material is broken down and so it builds up.”
• I know that fall doesn’t start officially until Sept 22 in 2024. Technically I should call this post “Late Summer Lawn Plan” rather than “Fall Lawn Plan”. But Fall Lawn Plan sounds better ;))