# Mowing short for overseeding



## Auggiedogg (Aug 27, 2019)

I will be overseeding my lawn in a couple weeks and I know that I am supposed to cut as short as my mower will allow and bag clippings before overseeding. I was just starting to gradually lower the mower deck to get down to the lowest height without shocking the grass, but then it occurred to me that perhaps shocking the existing grass is exactly what you want?

Currently I have my mower deck set at 3.75", although the real cut height is more like 3.5". It will go down to about 1" at the lowest setting. So, should I gradually get lower, or keep mowing high until right when I am going to overseed? Do I want to shock the existing grass so that it doesn't grow too fast after overseeding and keep the sun away from the seedlings?

I admit that I've only done a quick search, but I could look for hours or just post the question and tolerate the mockery, lol.

Also, I am on a corner lot and our subdivision roads are asphalt. So the grass around the edges of the yard tend to get burnt up pretty quickly. I was going to overseed with a *** blend, but I'm wondering if maybe I should mix in some more heat tolerant grass around the street. I do have underground irrigation. Sadly, it is a Toro System 11 hydraulic unit that works just fine, except for the timer. I have to manually advance from zone to zone, which will make initial watering 2-3x/day a bit of a trick.

Thanks. Great site with great information.


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## Harts (May 14, 2018)

I just take mine down all at once. It looks terrible but it also shocks the grass, which isn't a bad thing. It will grow back just fine especially with all the water it's going to get.


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## Auggiedogg (Aug 27, 2019)

Harts said:


> I just take mine down all at once. It looks terrible but it also shocks the grass, which isn't a bad thing. It will grow back just fine especially with all the water it's going to get.


Okay, that's why I double-checked. Shock the grass to minimize competition with the new seed. Since I'm overseeding with KBG (21-28 day germination), should I keep mowing at the lowest height until the seed germinates and is about the same height?


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## Chris LI (Oct 26, 2018)

I think you got your answer already, but yes, scalp it! Also, if you have time to the scalping day, stop irrigating immediately. Unless you're using PGR, you want to make the existing turf to go dormant, if possible, to slow down competition. Don't worry, you won't kill your lawn. If you lose a little bit, it wasn't the strongest, anyway (Darwin).

If you have a manual reel mower (or can get your hands on one), start mowing after decent germination, but don't wait too long. You want to keep the existing turf in check, so your grass babies don't get shaded out.

If you don't have a reel mower, make sure your rotary is in mulch mode, so you don't suck up any seed, and provide cover/nutrition.

For fertilizer, wait until germination, to drop starter fertilizer (you can drop Milo sooner-slower relase). You want to feed the seed, not have everything go to the existing turf.


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## Harts (May 14, 2018)

Once seed is down, I wouldn't mow. Only after germination when the seedling reach approx 2". You'll want to take it down to 1.5" to promote tillering. There is already inherent risk with a kbg overseed. You want to give the seed as much of a chance to germinate without disturbing the area.

If you have pgr or can get it easily, I would highly recommended it. Spray it 5 days prior to seeding to keep existing growth to a minimum.


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## g-man (Jun 15, 2017)

Check the cool season guide for a link to the overseed guide. In it you will find that technique of mowing short at once to stun the grow.


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## Auggiedogg (Aug 27, 2019)

I'm thinking of scrapping the KBG overseed idea. I'll just use a good mix like this one https://www.seedsuperstore.com/catalog/p-100002/ss5000-sunny-mixture?zip=49301&type=sunny.

Still 60% ***, but also has the TTTF and TTPG. All elite varieties. If I decide that I HAVE to go with a full KBG turf, I will do a complete reno. I few more hours crawling around the forums has given me a much better perspective.

One last question (for now). One side of my house is very shady and tends to get moss. This then transitions to the other parts of my yard which tend to grow really thick turf and are mostly sunny. How do you make the transition from sunny mix to the highly shady part?


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## SNOWBOB11 (Aug 31, 2017)

That mix is still heavily KBG but does give you a better chance at a successful overseed with the other faster establishing grass types mixed is. As mentioned by others I'd recommend sprayer PGR to give you the best chance at the KBG not being crowded out by your existing turf.

One thing to note is that mix contains chewing fescue and not TTTF. The chewing and fine fescues are very shade tolerant grasses. I'd use the same mix in the shady areas as the sunny ones and see how it does before you use a different grass type in one part of your lawn.


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## Auggiedogg (Aug 27, 2019)

thx snowbob11. I'm going to use some t-nex to keep the grass low without having to mow it for as long as possible. As for the shady area of the lawn, it already is composed of very different grass type. About the only grass left alive there looks to be fine fescue. And moss.....


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## Khy (Jul 27, 2018)

I'm also with the 'scalp it all at once' crowd. It definitely does shock the existing turf a bit and slows growth a tad. And it will look absolutely horrible for the first 5-6 days. But it grows out pretty fast still and honestly that "shock" to the system in my view results in healthier growth after the fact anyway.

I scalped mine down to 2" from 5" 2 weeks ago now when I did my TTTF overseed, I'd say the existing turf is up around 6" now and the seedlings are floating around 2-3" give or take. My intent is to mow sometime this week when I get the chance and take it back down to 3" again then drop some starter fert out to give everything a nice little kick.

Just be sure you have a lot of time on your hands as scalping half your HOC fills up your bag QUIIIICCCKKK. It'll literally feel like you're taking 6 steps and emptying your bag.


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## Suburban Jungle Life (Mar 1, 2018)

I scalped from 3.5" to about 1". As fast as that bag fills up, a blade stop would be nice...


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## Kaba (Mar 29, 2019)

I took a slightly different approach, I scalped and bagged to about 2", dethatched and scalped again to 1.5" (all in one morning) because I wanted to suck up anything left behind by the dethatcher (and going down the extra 0.5" was easier to see where I mowed).

I was coming down from about 4"


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## Suburban Jungle Life (Mar 1, 2018)

Kaba said:


> I took a slightly different approach, I scalped and bagged to about 2", dethatched and scalped again to 1.5" (all in one morning) because I wanted to suck up anything left behind by the dethatcher (and going down the extra 0.5" was easier to see where I mowed).
> 
> I was coming down from about 4"


Kinda like this idea! I'll have to try it out.


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## NJ-lawn (Jun 25, 2018)

Harts said:


> Once seed is down, I wouldn't mow. Only after germination when the seedling reach approx 2". You'll want to take it down to 1.5" to promote tillering. There is already inherent risk with a kbg overseed. You want to give the seed as much of a chance to germinate without disturbing the area.
> 
> If you have pgr or can get it easily, I would highly recommended it. Spray it 5 days prior to seeding to keep existing growth to a minimum.


Do we really need to wait that long after spraying T-Nex? I was hoping to scalp in a day or two.


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## social port (Jun 19, 2017)

Khy said:


> Just be sure you have a lot of time on your hands as scalping half your HOC fills up your bag QUIIIICCCKKK. It'll literally feel like you're taking 6 steps and emptying your bag.


So true! This is the most difficult thing about overseeding, IMO.


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## Khy (Jul 27, 2018)

NJ-lawn said:


> Harts said:
> 
> 
> > Once seed is down, I wouldn't mow. Only after germination when the seedling reach approx 2". You'll want to take it down to 1.5" to promote tillering. There is already inherent risk with a kbg overseed. You want to give the seed as much of a chance to germinate without disturbing the area.
> ...


No, you don't have to wait. It's just a matter of wanting it to get fully into the leaf tissue as much as possible prior to seeding and starting your heavy watering schedule. If you're able to scalp, T-Nex, wait 3-5 days, cut back to scalp height. That's 'ideal' but you can also literally just scalp down, t-nex and then the next day seed and start your watering and all.

T-Nex own label recommends waiting 1-5 days. But it won't effect seed germination at all.


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## Harts (May 14, 2018)

^+1. It takes approx 5 days for the PGR to start suppression. Seed any day you want.


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## NJ-lawn (Jun 25, 2018)

Just throwing this out there but why not scalp then spray T-Nex. I thought I read somewhere PGR works better on short mowed grass?

Or am I splitting hairs again....


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## g-man (Jun 15, 2017)

Pgr Is absorbed thru the leaf. You want growing leaves to absorb it and not the scalped brown stuff. Spray it first, wait 4hrs and then scalp.

My general disclaimer, im not an overseeder, so no real experience with this.


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