Cool Season Overseed Guide

Cool season grasses like Kentucky Bluegrass, Fescue & Rye
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ForsheeMS
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Cool Season Overseed Guide

Post by ForsheeMS »

Introduction
There seems to be a lot of interest here on the forums for an overseed guide so I’m going to give it my best shot. Keep in mind, this is primarily for TTTF or PRG lawns. Some of these ideas will work with KBG but that’s a totally different animal so someone with more KBG experience could do a separate write up for that. I’m no professional and this guide is comprised of techniques I’ve tried over the years and has worked very well. Every lawn is a little different so slight adjustments or changes might need to be made for each individual situation but this should be really close for anyone overseeing a TTTF or PRG lawn.

First let me say this. One of the most important things you can do for your lawn is a soil test. I won’t go into a lot of detail here but if you’re going to put effort into making your lawn better this is the easiest and cheapest way. If the soil does not contain the proper balance of nutrients nothing else you do will make it any better. Guessing here is only going to cause pain, suffering and bad results.

Seed selection: I start with good quality seed that is 100% free of weed seeds. No sense in starting out with weeds. Yes, it will cost a little more but will be well worth it come next spring when you have a beautiful weed free lawn. There are several well known companies that sell quality seed. I’ve had good luck with The Hogan Company. With coated seeds, you are paying more for less seeds (50% seeds/filler), so must of us avoid them.

Overseed:

First thing to do is cut the existing grass low. The term “low” is relative to the HOC where you normally keep your lawn. During the summer months I stay between 4” to 5” so for me 2.5” to 3” is what I consider low. If you keep your lawn at 3” then you may want to go down to 1.5” for the overseed. The idea here is to throw the existing grass into shock which will slow or stop growth for a week or two. This will give the seeds time to germinate and get some height so it is able to compete with the existing grass. If you have a bagger you can do this in a single cut bagging and removing the clippings. Without a bagger, you will need to make multiple passes lowering the cut with each pass until you reach the desired height. Hopefully you know your mower well enough to know how much grass it can remove at once without leaving excessive clippings. At this point the grass will likely be pale and stemmy looking. That’s ok because in a few weeks it’s going to look amazing!

Aeration: Some folks don’t believe in aeration while others go completely overboard with it. If the soil isn’t compacted then you probably don’t need to aerate. I have had certain areas where the soil was easily compacted. Typically what I do with those areas is make one pass with the aerator, then spread a light coat (1/4” to 1/2”) of compost, then make two more passes with the aerator. Outside of extremely bad cases this make a huge difference with problem areas. It’s been years since I’ve aerated the entire lawn. Instead I only do the problem areas.

Fertilizer: There is really no need to drop fertilizer at the time of an overseed, especially anything with nitrogen. Everything the new grass needs for the first few weeks of life is contained in the seed. At this point you have cut the existing grass low in an effort to slow its growth so the new seedlings can catch up. Adding nitrogen at time of seeding will give the existing grass a boost causing it to outgrow and try to choke out the new seedlings. Don’t do it! Even Milorganite can cause this issue. The only exception would be organics such as alfalfa or soybean meal which take two to three weeks to kick in and cause top growth. I do add 0-25-25 at time of seeding. Normally I do 1 lbs of 0-25-25 per 1k at time of seeding which helps promote root growth. This is fine, just don’t put down any nitrogen. If your soil test shows that P and K are high skip this step.

Seeding: The typical overseeding rate of TTTF and PRG is 4lbs per 1k. What I do is first hand seed any small bare spots and then use the spreader. I will completely skip any areas where the grass is already thick. No sense in putting seed down where you don’t need it. I use one of those over the shoulder bag type spreaders. With this spreader I can easily regulate the amount of seed coming out. I go a little heavier in really thin areas and lighter in the areas that don’t need as much. The key is to maintain a good thick turf but not so thick that it chokes itself out. As mentioned at the beginning, a good quality seed is best.

Pressing the seed into the soil: Seed to soil contact is extremely important to good germination. After spreading your seed it’s time to go over it and press it into the soil. If you have a really small lawn, get the family out and have them walk over the newly seeded area. For larger lawns, you can rent a lawn roller and go over the area with that. You can also go over the lawn with a riding mower using the tires to press the seed in. The goal here is to press the seed into the soil no matter how you do it.

Water: In order for seed to germinate it must have sunlight and moisture. Moisture is the key word here. You don’t want to drown the new seed. Watering lightly anywhere from 2 to 5 times per day just enough to keep the seed moist. Temps, humidity, and the amount of direct sunlight on the seeded area will effect how quickly the seed and soil dry out. If you get this right and keep it moist you should start seeing germination in 5 to 7 days. Keep watering this way for 2 weeks which is when germination should be complete.

First Mow: Following this guide your first mow should be about 2 weeks after seeding. In my experience, the new grass is up to about 3.5” at this point and I will cut it back to 3”. Make sure your mower blade/blades are razor sharp. While the new seedlings are about as tall as the existing grass the roots are still developing and can be quite shallow. The first cut is going to pull up a few seedlings but a dull blade will pull out even more. Also be very careful when making turns as the slightest mistake can do damage. This is also the time to back off on watering. Slowly wean the new grass off by watering once a day to every 3 or 4 days depending on temps.

Fertilizer: After the first cut is when I slowly start fertilizing. For this I use urea. It’s relatively inexpensive and by this time the temps are generally cool enough that you don’t have to worry about burn. First and second app is 1/4lbs nitrogen per 1k a week apart. Each app has to be watered in with at least 1/4” of water. Mow as needed. After the first two nitrogen apps you can incease it to 1/2lbs nitrogen per 1k every two weeks.

I hope this helps some folks out and prevents some of the common mistakes. Trust me, most of what I’ve learned was done the hard way with a ton of mistakes and some of them were pretty costly.
Last edited by g-man on Sun Sep 23, 2018 9:13 pm, edited 1 time in total.

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social port
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Re: Cool Season Overseed Guide

Post by social port »

Thank you for writing this up! We've needed a guide on overseeding, and this will be a valuable resource now and in the future. Many thanks to you!

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Re: Cool Season Overseed Guide

Post by ken-n-nancy »

Thanks, @ForsheeMS for being willing to take a stab at writing this up. I think this is excellent!

Are you game to have some collaboration help on making some updates? If so, there's a couple things I'd be inclined to have a go at myself that you could then cut-and-paste into the article, or that you may want to write up yourself, that I had envisioned including in the "Cool Season Overseed Guide." Below is a little more on each of these:

First, a paragraph on "Should you overseed?" that addresses whether or not overseeding is right for you. I think that things like current grass type, current grass density (pictures taken down into the lawn from eye-level would help show varying levels of density), and maybe goals/objectives would help out in this paragraph. I've seen here that some people have varying expectations of what they're trying to get from an overseed - some of which are spot-on, and others of which are not going to lead to satisfaction.

Secondly, and, you already hinted at this, a paragraph on KBG overseeding. Personally, I think this paragraph would be mostly reasons to expect KBG overseeding to not work well -- I've tried various overseeding attempts with KBG and never had any of them provide much, if any, satisfaction, with the exception of "patch repair" which really isn't what I consider to be overseeding at all.

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ForsheeMS
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Re: Cool Season Overseed Guide

Post by ForsheeMS »

@ken-n-nancy I have no problems adding, editing, or making changes to any of it. In writing it out my intentions were that it’s strictly a guide and nothing set in stone. Over the years I’ve tried many different ideas. A few of the worked, some didn’t and a lot of them failed miserably. I’m always open to new ideas and this forum is a great place to learn from others success and failures.

With that said, this thread would be a great place to see others ideas. If I try any ideas that work in the future I will definitely add that here as well.

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Re: Cool Season Overseed Guide

Post by Green »

Nice. The only edit I'd make is about fertilizer. If someone's soil test says theyre low on P, they should add some phosphate in with the urea, e.g. Milo or starter fert.

As far as KBG seed, it does work well for patch repairs if you give it enough time.

A lot of my overseeding this year has been more like patch repair.
Last edited by Green on Sun Sep 23, 2018 7:48 pm, edited 2 times in total.
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Re: Cool Season Overseed Guide

Post by Abru »

Hello ForsheeMS,
Thank you for your guide. It'll be helpful when I start overseeding my Tall Fescue lawn this fall.
I have a question regarding the timing of overseeding. I know that each bag of seed has recommended air/soil temperatures for the time of overseeding, but I am curious about your experiences with different temperatures at the time of seeding.

Is it unwise to start overseeding when temperatures are still in the 80's? Where Iive, recommended seeding temperatures may not arrive for a while, but I want my lawn to get decent amount of time to develop before winter is here.

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Re: Cool Season Overseed Guide

Post by erickdaniels »

@ForsheeMS Can you PLEASE share some of your overseed screw ups for our education??? I feel like I’ve also made mistakes over the years; some of which make me nervous even now. I think my worst mistake was using urea, in late summer, and not watering in... yikes what a mess!

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Re: Cool Season Overseed Guide

Post by g-man »

I created a link from the Cool Season Guide to point to this Overseed guide. Great work!

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Re: Cool Season Overseed Guide

Post by Virginiagal »

Great advice, well written! Maybe you could add some advice on what to do about weeds before you start and keeping them down during the germination period. Maybe give some advice on dealing with things that go wrong, like gully washers. I am on my third try this fall because of Florence and other deluges.

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Re: Cool Season Overseed Guide

Post by Hoosier »

Great guide... I just finished about 20 hours of overseed/fixing problem areas this weekend. One of the things that I did was mow really low, and then use a dethatcher/power rake to pull up all of the dead grass. Ended up filling 15 lawn bags just for about a 5500 sf area of my yard. I thought this was necessary, as I had so much that the seed wouldn't have had any soil contact in a lot of areas. The reason for all of this dead grass mixed in is obviously for another thread, but just adding to your note of seed to soil contact, that some people may require more than just a low mow.

The reason for the dead grass, is that I realized I have a grub issue, despite a preventative app in June. So, one of the things that might help for the guide, is the addition of some common problem indicators to look to address before seeding? For example, any bare areas that seem to die off or thin out each year? (probably rocks or something under the soil that should be dug up) Any other damage spots to investigate? In my case, grubs, rather than just dried out/dormant grass, but other common things may be dog pee areas where the grass is burnt.

Aside from that, one more comment - I used peat moss for the first time this year as a topper in any areas that were especially bare after pulling all of the dead grass out. In previous years, I hand sprinkled compost over those areas to lightly cover the seed. Compost has worked well for me, but really liked how easy it was to spread the peat moss with a plastic rake, even without a peat moss roller, so interested to compare results.

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Re: Cool Season Overseed Guide

Post by LawnNeighborSam »

Great information @ForsheeMS

I just overseeded for the first time with midnight KBG and the turf is thickening up like crazy and the bare patches are filling in. 80% of the lawn around my house looks beautiful.

One of the problems I have is the entire backyard is shaded heavily with trees. We will be taking those trees down after winter but it stays moist for days there using very little water and barely gets any sun. It goes from thick to thin on a monthly basis and it seems the overseeding didn’t help because KBG needs lots of sun.

Am I correct? Thoughts @ken-n-nancy?
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Re: Cool Season Overseed Guide

Post by Suburban Jungle Life »

PGR?

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Re: Cool Season Overseed Guide

Post by MMoore »

Suburban Jungle Life wrote:
Mon Sep 24, 2018 8:42 am
PGR?
PGR would help shaded areas?

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Re: Cool Season Overseed Guide

Post by Suburban Jungle Life »

MMoore wrote:
Mon Sep 24, 2018 11:36 am
Suburban Jungle Life wrote:
Mon Sep 24, 2018 8:42 am
PGR?
PGR would help shaded areas?
Probably not. Just a suggestion to add a section for PGR when overseeding.

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Re: Cool Season Overseed Guide

Post by GoPre »

Suburban Jungle Life wrote:
Mon Sep 24, 2018 8:42 am
PGR?
A must if overseeding with KBG.

Nice work and thanks a ton!

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Re: Cool Season Overseed Guide

Post by ericgautier »

Nice work @ForsheeMS ! :thumbup:
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Re: Cool Season Overseed Guide

Post by Creppin »

What’s everyone strategy/success stories with PGR. I haven’t used before, but did get some T-Nex for the fall. I’m going to try the KBG overseed. Was going to cut a few days before apply PGR and the cut low the day of seeding say 3 days after the PGR app.

Any thoughts or success on the KBG overseed will be a welcomed read!

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Re: Cool Season Overseed Guide

Post by Greasmatta »

Thank you for the guide. Being a newbie, so i don't need to put top dressing on the seeds?
What about sand? Can I overseed directly on the grass and then put sand on it for leveling?

I want to level my lawn with sand, would be great if I could overseed at the same time.

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Re: Cool Season Overseed Guide

Post by Ylli »

Creppin wrote:
Wed Jul 03, 2019 12:41 pm
What’s everyone strategy/success stories with PGR.
PGR or PRG (Perennial Ryegrass)?

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Re: Cool Season Overseed Guide

Post by Creppin »

Ylli wrote:
Wed Jul 03, 2019 2:47 pm
Creppin wrote:
Wed Jul 03, 2019 12:41 pm
What’s everyone strategy/success stories with PGR.
PGR or PRG (Perennial Ryegrass)?
PGR - how much and when before you overseed. 1 week, 2 weeks before? Day of? Figured timing

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