For those of you with cool season grass, Kentucky Bluegrass, perennial ryegrass and turf type tall fescue, the big push this time of year is aeration and over-seeding. The pressure to burn down the lawn and start over is real.
Many of you take my advice and work with your existing lawn to aerate and overseed it to make it thicker and thicker. I have an entire guide I wrote that takes you through how to seed your lawn, step-by-step.
But what about if your lawn is already thick, should you still seed?
My answer would be “no.”
There is absolutely no reason to seed your lawn if it’s already thick and healthy. I started my turf type tall fescue lawn in NW Indiana from seed on bare ground in 2005 and never seeded it again. Look at all my videos over those years and you will not see any overseeding at all, but you will see a VERY thick lawn. (you also won’t see any mechanical aeration)
Another category of folks would be those of you who maybe have some thin areas in the lawn but overall, it’s come long and is looking pretty good. Let’s say you are 75-80% of the way to that thick lawn you desire. Do you need to seed the lawn?
My answer there would also be “probably no.” In this case, it’s a judgement call on your part but seeding may not be necessary, especially if you are in a crunch for time or budget.
The final category of folks who may be reading this are those of you who, no matter what shape your lawn is in, you have had outbreaks of poa-annua (annual bluegrass) in your lawn. Annual bluegrass germinates in the fall time, grows a little, hibernates over winter, rages in spring and drops seeds in summer. It lives fast and loose and continues to get worse and worse year over year. It’s a major problem for some folks, very similar to crabgrass, but just lives on a different schedule.
Also in this category are those of you who fight weeds like chickweed, hairy bittercress and/or henbit in your lawns.
These are all referred to as “winter annual weeds” which means they germinate in the fall and rage the following spring into summer. You can stop them, but in order to do so, you cannot throw down grass seed in the Fall time. So the strategy below is for sure for you.
Cool Season Lawns - Fall Steps - No Seeding
To understand the approach here, let’s look at how cool season grasses grow. This is a chart showing the nature of cool season grasses by season.
Get A Thicker Lawn This Fall
Some of you may be coming off of a challenging summer season. In some cases, if the heat was high and water was scarce, the lawn may have gone dormant and brown in many areas. The good news is that in the fall time it’s going to wake back up naturally and start pushing top growth and roots again. The strategy below helps you maximize that natural growth spurt.
If your lawn is already thick, it just gets greener and grows deeper, denser roots. If your lawn is still a little thin, it will help fill in the thin areas quite quickly.
Prevent Weeds and Poa Annua
The other piece of this strategy is defensive and entails pre-emergent herbicides to stop the winter annual weeds. Most of these weeds will germinate as soil temps fall to 70F coming out of summer and continue through most of the fall time.
A pre-emergent herbicide goes down prior to this time and kills the young weeds just as they germinate so they can’t invade the lawn. Pre-emergents don’t stop every weed, but they are very effective on the ones mentioned here: poa annua, hairy bittercress, chickweed and henbit.
You will not notice the results from the pre-emergent applications until the following spring when you don’t have these invaders dropping seeds and your neighbors do.
The reason you can’t throw down grass seed in this scenario is that the pre-emergent will not only stop the weeds, it will also kill your young grass as it tries to grow.
So in summary, this fall strategy is for cool season lawns and will help you thicken the lawn up if needed as well as prevent invasions from fall/winter annual weeds like annual bluegrass and others.
Soil Temperatures Matter
I mentioned above that the 70F soil temp is the trigger that tells you when to start due to the germination of the weeds. The best way to know the soil temperature of your house is to use my free app that you can get on Android and Iphone. In fact, the app will even tell you exactly when to throw down and the strategy below will match up with it pretty nicely.
Step-By-Step Fall Application Plan
Step 1 - as soil temps fall to 70F
- Apply 24-0-6 Flagship, 3lbs/1,000 sq ft
- Apply Dithiopyr pre-emergent 4lbs/1,000 sq ft
- Apply Air8 Liquid Aeration, 9oz/1,000
Notes: Here we have fert to give you a VERY nice green color and stimulate rooting and thickening plus some pre-emergent to stop the weeds mentioned. If you don’t want to get crazy with tracking your soil temps, just throw these down at the end of August, you’ll be fine.
You can apply all of this on the same day and water them in together with ½” of irrigation. For the granular stuff, make sure to do two separate applications. Don’t mix them together in the hopper.
Many of you will be using dithiopyr here in the fall but if you have prodiamine leftover from the spring, use that up first, it will work the same.
Step 2 - 4 weeks after step 1
Apply 24-0-6 Flagship, 3lbs/1,000
Apply Air8 Liquid Aeration, 9oz/1,000
Notes: We have more fertilizer to keep things moving plus some additional liquid aeration to loosen compacted soil. The Air8 also contains humic acid which is a carbon source for the soil.
Step 3 - 4 weeks after step 2
Apply 24-0-6 Flagship, 3lbs/1,000
Notes: If you live further north such as North Dakota or Maine, this is likely the very last application you will do and you can call it your winterizer. If you live somewhere further south in the transition zone like North Carolina, Tennessee or Virginia, likely your lawn is still growing a bit. You also have a MUCH bigger threat from the fall weeds like annual blue grass so you guys should add this to your strategy along with the Flagship.
- Apply a second application of pre-emergent to get you through winter. Dithiopyr, 4lbs/1,000
Essentially, you want to continue applying Flagship 24-0-6 every 4 weeks until your soil temps fall below 50F. It’s at that point you pause for a bit, wait until they drop to around 40-45F and that is when you apply your final winterizer.
So there you go, this is the plan you run if you have cool season grass and are not planning to seed the lawn. Be sure to take pics before you start this strategy so you can map your progress. I bit you will be surprised just how much improvement you get!