# overseeding - N, P, K?



## Bkell101 (Jun 25, 2018)

Hi All,

When do you put down a starter fertilizer or any other products when overseeding?

LCN method: 
seeds + lesco starter (18-24-12) + milorganite 7lbs/1000sq ft

vs

Recent TLF poster: 
seeds + 0-25-25 (withhold N)
then later on around time of first mow some organic fertilizer

I guess argument is reduce competition of the new seed? Adding N would make the existing grass grow and out compete the new grass?

What are your thoughts?


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## g-man (Jun 15, 2017)

Yes. Plus the new seed wont need or be able to use the nitrogen right away.

Also first mow should be at around 2in (1.5in if your mower can go that low) to encourage fill in. Mow at this height for 3-4 mows.

Source of mowing height:
https://www.extension.purdue.edu/extmedia/AY/AY-3-W.pdf


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## jaygrizzle (Jun 6, 2018)

@g-man does withholding the N apply to overseeding/seeding fescue or does that just apply when using KBG?

The reason I ask is I was going to to use the Scotts starter fertilizer with Tenacity, but it says it is 21-22-4. Why would they include that much N in their starter fertilizer if new seed can't even use it?


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## ForsheeMS (May 21, 2018)

Maybe my earlier post wasn't as clear as it should have been so I'll try to be a little more thorough here.

Grass is TTTF. Typically I cut from 4" to 2.5" the day of overseed. If you don't/can't bag the clippings you will need to make multiple passes lowering HOC each time. Otherwise you will have a mess. Once this is finished your fescue is going to look very pale and stemmy and is basically in shock.

From there you can aerate if you wish. I've done it both ways and really don't see much of a difference. Main time I aerate is if I spread compost. If so I will aerate after the compost is down. This pushes some of the compost into the soil.

Next is drop the seed. For a standard overseed when the lawn is still in pretty good shape I do 4lbs of TTTF seed per 1k. Of course any really thin or bare spots get extra seed by hand. After seeding I put down 0-25-25 at about 1/4 to 1/2lbs of each P & K per 1k. You can do more or less depending on your soil test results and if your test results show P & K to be good you can skip it. No N is put down at this time. *The exception to no nitrogen at time of seeding* is sometimes I will put down alfalfa (rabbit pellets) at about 20lbs per 1k. It takes alfalfa right around 3 weeks to be broken down and available as nitrogen so it will not cause rapid growth of the existing grass.

Once everything is on the ground and just before turning the sprinklers on go over the entire lawn with a lawn roller, ATV, riding mower or whatever you can come up with to press the seed into the soil. I think the most important part of seeding is good seed to soil contact.

As long as the seed stays moist I see germination in 5 to 7 days and the first cut is around 2 weeks. My first cut is at 3" and most of the new seedlings get trimmed. After the first cut I will drop urea at 1/4 to 1/2lbs N per 1k depending on temps. As long as temps are cool and the grass gets water urea is much safer than a lot of folks think. Just double check all your numbers and be sure your rates are correct. I try to drop urea anytime we will get rain all the way into mid November. My final winterizer app is normally late December to early January at 1lbs N per 1k.

Again, this is for TTTF. I really have no experience with KBG but don't see why it wouldn't work with it too.


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## g-man (Jun 15, 2017)

@jaygrizzle ^what ForshessMS said. His approach, and I agree with it, is that providing nitrogen in an overseed is going to feed the existing lawn. That makes the current lawn grow and forces you to mow.

Scott product is really meant for starting from bare dirt. It is being used by folks to take advantage of the tenacity it has. I'm not sure why Scott places so much nitrogen. I've never checked if it is mainly slow release. Some stuff Scott does makes no sense to me (ie. Summer nitrogen).

If your lawn is kbg, then you dont need to do any of this (no overseed). Just feed it nitrogen all fall and it will spread and fill in.

I think we are in need of a Overseed article with detail steps/best practices. I think ForshessMS has a good draft in this post. The step of pressing the seed into the ground is a very important one that most dont do.


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## jaygrizzle (Jun 6, 2018)

@ForsheeMS what are you using for 0-25-25? I am not having much luck finding anything. The phosphate and potassium products I've found say that they are just for use on plants and not for lawns.


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## ericgautier (Apr 22, 2017)

@Bkell101 look into spraying a PGR the day before you overseed. It is a game charger.


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## social port (Jun 19, 2017)

@g-man I think that an overseeding guide would be very helpful, and I really like the one offered here by @ForsheeMS .
But overseeding is done in various ways, right?

To that end , I wonder if we could couple @ForsheeMS 's method with that of another forum member who has had years of experience with successful overseeding? We would then have two alternative methods of effective overseeding practices.


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## ForsheeMS (May 21, 2018)

jaygrizzle said:


> @ForsheeMS what are you using for 0-25-25? I am not having much luck finding anything. The phosphate and potassium products I've found say that they are just for use on plants and not for lawns.


Check with your local feed and seed places. You know, the places the farmers go to get their stuff. Once you understand the N P K numbers and how to use them you can put your own mixes together to get what you really need plus it's way cheaper. The brand name stuff at the box stores normally end up giving you more then you need of one nutrient and not enough of the other so it's good to have options.


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## ForsheeMS (May 21, 2018)

ericgautier said:


> @Bkell101 look into spraying a PGR the day before you overseed. It is a game charger.


I've never used PGR but have thought about it more for the summer months and drought resistance. With TTTF overseeding and doing the shock cut I really don't think it's needed but probably wouldn't hurt. I've found it takes at least a week for the TTTF to begin recovering and a good 2 weeks before you see any noticeable growth. At that point the seedlings should already be up and catching up to the height of the existing grass.

Now for KBG it would almost be a necessity due to the longer germination time.


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## Ridgerunner (May 16, 2017)

Please allow me to muddy this up for you.  
The seed, like an egg, contains all of the nutrients needed by the plant to develop for 2-4 weeks after germination. After which the turf has enough maturity to start drawing nutrients from the soil. The theory behind applying a starter fertilizer, is to supply the young plant with readily available nutrients for that time.

The debate:

Apply NPK prior to seeding. 
1. This allows you to stay off the grass and prevent tearing up the shallow rooted new turf.
2. This allows the nutrients, especially slower movers P and K, time to work down into the top of the soil where the new plant's root will be able to access it rather than laying unavailable .on the surface if applied later, once it is safe to walk on the new turf.

Apply NPK 3-4 weeks after germination.
1. If one is careful, you can walk on newly germinated grass 3-4 weeks after it has germinated without doing significant damage to the turf.
2. Makes nutrients, particularly N, more available at the true time of plant need and plant ability to absorb it. Avoids concerns that pre-applied N will have leached out and that the P and K applied before seeding will get tied up in the soil and be less available.
3. Applying N prior to overseeding an established lawn will promote topgrowth of existing turf that will shade out the seed and reduce germination.

Apply noting until after the second or third mow, then spoon feed with N thereon out.
1. Starter fertilizers don't make a difference for soils that aren't nutrient deficient. Turf germinates and grows just fine without additions of "starter" NPK.

Then there is the debate between applying an ammonium fertilizer vs a nitrate.
BTW, some studies also show that HA application can improve results.


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## g-man (Jun 15, 2017)

@social port There are always multiple way to do lawn care. Some items are just a different opinion (aerate?). I dont overseed, so I cant give much experience but I think you all could collaborate and develop an Overseed Guide.

I would think there are a couple of main themes that we could all agree on with different approaches to each. For example:

- seed selection (TTTF, PR, KBG) and sourcing (Hogan, seed super store, preferred seed)
- soil to seed contact (mow low and bag? dethach? slit seeding? rolling? etc)
- watering (keep it moist but no fungus)
- seed covers (peat moss? soil moist?)
- fertilizer (scott weed? liquid tenacity? 0-50-50)
- mow (2in? when?)
- herbicides and preM (when to use what?)

I think the collective experience of our members could make an awesome guide.


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## social port (Jun 19, 2017)

@Ridgerunner What makes me do a double-take is the idea of overseeding without N at seeding time. And then I do a _triple-take_ upon learning that the seed basically has the essential life-sustaining nutrients in it already for 3-4 weeks. On the one hand, that simply makes sense. On the other hand, I think many of us have been conditioned to add fertilizer at the time of seeding -- with no questions asked.
Thanks for chiming in here. I really like seeing both sides of the argument.



Ridgerunner said:


> This allows the nutrients, especially slower movers P and K, time to work down into the top of the soil where the new plant's root will be able to access it rather than laying unavailable .on the surface if applied later,


This really shows the wisdom is @ForsheeMS 's approach: Provide P and K at the time of seeding in order to give them time to work into the soil.


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## social port (Jun 19, 2017)

g-man said:


> @social port There are always multiple way to do lawn care. Some items are just a different opinion (aerate?). I dont overseed, so I cant give much experience but I think you all could collaborate and develop an Overseed Guide.
> 
> I would think there are a couple of main themes that we could all agree on with different approaches to each. For example:
> 
> ...


Hmm...I've been thinking a lot about overseeding recently. I just may start a draft. I can think of plenty of potential contributors who have a lot of experience.


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## jha4aamu (Oct 16, 2017)

social port said:


> @Ridgerunner What makes me do a double-take is the idea of overseeding without N at seeding time. And then I do a _triple-take_ upon learning that the seed basically has the essential life-sustaining nutrients in it already for 3-4 weeks. On the one hand, that simply makes sense. On the other hand, I think many of us have been conditioned to add fertilizer at the time of seeding -- with no questions asked.
> Thanks for chiming in here. I really like seeing both sides of the argument.


about 2 weeks ago i started pre germinating seed, soaking it in water a few days before throwing it down in some bare spots. well, i threw about half of it down and left the other half in the bag on my porch and completely forgot about it. walked out there last night and had a bag full of beautifully germinated prg. definitely made me rethink the importance of these "starter" fertilizers.


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## Ridgerunner (May 16, 2017)

social port said:


> @Ridgerunner What makes me do a double-take is the idea of overseeding without N at seeding time. And then I do a _triple-take_ upon learning that the seed basically has the essential life-sustaining nutrients in it already for 3-4 weeks. On the one hand, that simply makes sense. On the other hand, I think many of us have been conditioned to add fertilizer at the time of seeding -- with no questions asked.
> Thanks for chiming in here. I really like seeing both sides of the argument.
> 
> 
> ...


I think I'd stick with the 2-4 week range estimate. :mrgreen: Not sure it would be wise to assume a 3-4. The point is, that a starter fertilizer isn't needed for germination and wont be employed by the plant until it has developed sufficiently anyway. The arguments regarding starter fertilizer and application timing aren't mine, I'm just the messenger for what I've read.



jha4aamu said:


> social port said:
> 
> 
> > @Ridgerunner What makes me do a double-take is the idea of overseeding without N at seeding time. And then I do a _triple-take_ upon learning that the seed basically has the essential life-sustaining nutrients in it already for 3-4 weeks. On the one hand, that simply makes sense. On the other hand, I think many of us have been conditioned to add fertilizer at the time of seeding -- with no questions asked.
> ...


I didn't intend to discount the application/use of starter fertilizer. I'm a belt and suspender type of guy myself, so, if starter isn't over applied, it wont hurt the turf and I'd take the chance that it might help, what's to lose? I think @ForsheeMS has an excellent approach using P&K in a light application at seeding, Then spoon feeding of N with regular irrigation after the first mow.
Next time I'm out, I'll ask the sod farmer what he does (timing wise). I know they swear by triple 10.


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## Bkell101 (Jun 25, 2018)

how long does the p and k take to get into the soil?


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## Bkell101 (Jun 25, 2018)

ericgautier said:


> @Bkell101 look into spraying a PGR the day before you overseed. It is a game charger.


I'm planning on it and ordered he biostim pack by lcn last night 😀


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## Bkell101 (Jun 25, 2018)

I think a guide is a fantastic idea.

I also think it's crucial for the experienced folks to go back to the basics and teach us what's needed for a new grass seed at each stage....

Seed -- germination needs what nutrients/elements?

Germination - first cut needs what nutrients/elements?

Then maybe I can understand reasoning easier.

Many folks have also said spring is time to get soil test, however it seems like a soil test sometime prior to overseeding would be prudent in order to determine what your needs may truly be. What do you all think?


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## ForsheeMS (May 21, 2018)

@Bkell101 I'll do the best I can to break it down.

_Seed -- germination needs what nutrients/elements?_ At this stage it really needs nothing but moisture. Keeping the seed moist is all it takes for germination to happen. Watering lightly 2 to 5 times a day to keep the seed and top layer of soil moist. The reason I say 2 to 5 times is it really depends on temps, humidity and wind. All of these have an effect on how quickly the soil will dry out. It's all a judgment call and the more experience you have the better you know how often to water.

_Germination - first cut needs what nutrients/elements?_ Once germination starts it still needs moisture. At this point the tiny root is barely in the soil. If you let that top layer of soil dry out for very long the seedling will quickly stress and die. Here you will continue watering multiple times each day. Once germination is complete you can begin to back off of the frequency slowly and begin watering longer. Watering longer at a time and less frequent allows the root to dig in a little deeper to gain access to the moisture in the soil. Stop watering about 24 hours before the first cut so both the grass and the soil can dry out a little. Make sure your mower blades are extremely sharp! Dull blades will pull some of the new grass up roots and all. Be as gentle as possible making turns to avoid damage. After the first cut I do a light nitrogen app (1/4lbs N per 1k) and water it in. By now you should be able to back off to watering every 2 to 3 days, more water each time but less often. You still need to keep temp, humidity and wind in mind when determining how often to water.

_Many folks have also said spring is time to get soil test, however it seems like a soil test sometime prior to overseeding would be prudent in order to determine what your needs may truly be. What do you all think?_ Spring is definitely a good time for a soil test. This gives you all summer to make adjustments if needed to get ready for fall seeding. Once you get the soil dialed in you only need to test every 3 years or so.


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## Bkell101 (Jun 25, 2018)

So seed to begin germinate: water
Beginning to end germination: water
End germination to first cut: water?
After first cut: nitrogen?

You mentioned P and K 0-25-25 application previously, but not in the breakdown above.
Just trying to map this out to understand, and not try to be a smart a** I promise.

Also, What marks end of germination? At this point you said you back off the watering so it seems important for me to be able to tell when germination is complete.

How do you determine when to cut? Height of new blades?

Also , you mentioned soil test in spring in order to prep soil and give it what it needs for fall overseed. Does this mean taking soil sample now in summer is too late to get the soil to where it needs to be at time of overseed (because it takes a while to prime and get the soil right)?


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## Ridgerunner (May 16, 2017)

Great guidance by @ForsheeMS . I would encourage him to compile the advice he gives here into a "guide" for overseeding. :thumbup:


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## ForsheeMS (May 21, 2018)

@Bkell101 First let me say this, none of this is really set in stone. There is no way anyone could write out a guide that must be followed to the "T" in order to achieve success. Most of this is seat of the pants, gut feeling kind of stuff with some trial and error (lots of error) and your own judgement mixed in. There are way too many variables that you will run into over time and mistakes will be made. Hopefully you learn from it, share your experience and keep trying. So, to try to answer your questions:

_So seed to begin germinate: water
Beginning to end germination: water
End germination to first cut: water?
After first cut: nitrogen?_

Yes, that's about it.

_You mentioned P and K 0-25-25 application previously, but not in the breakdown above.
Just trying to map this out to understand, and not try to be a smart a** I promise. _ No offense taken. If you did your soil test in the spring and made adjustments per that test over the summer then P and K really aren't necessary as these should be at the correct level anyway. If you mulch mow or discharge the clippings the P and K levels shouldn't change that much as the clippings are returning most of these nutrients back to the soil. Bagging is a different story since removing the clippings are also removing P and K. The rate I suggest at seeding (1/4lbs of P and K per 1k) is pretty light and will put these two nutrients where they are readily available for the seedlings. If your soil test indicated P and K in the higher than optimal range I would skip this app at seeding.

_Also, What marks end of germination? At this point you said you back off the watering so it seems important for me to be able to tell when germination is complete. _ Here is where gut feeling and seat of the pants combined with experience come in. For my TTTF I feel germination is complete at the 2 week mark. This is factoring in that I did my job keeping the seed moist the entire 2 weeks. Yes, you might get a little more germination after that point but for the most part it has done about all it's going to do in 2 weeks. Again, this is for TTTF which is what I have experience with.

_How do you determine when to cut? Height of new blades?_ Back in 2013 when I did a full reno on nearly 1/2 acre (this was a major undertaking but I'll save that for another post) I had germination beginning on day 5 and by day 7 there was a very green tint to the entire lawn. Exactly 2 weeks from seed down the new grass was about 3.5" tall overall. Yes, there were some spots that were lower and some that were taller but overall 3.5" was where it was at. It was cut back to 3" at that point. The main thing here is to not let the new grass flop over. Once that happens it's done. At the time we had no rain in the forecast. If rain was coming in I probably would have gone a little shorter because wet grass flops over easier than dry grass. This was on a reno. If you are overseeding into existing grass you can let it get a little longer because the established grass will help support the new grass. On an overseed I usually do the first cut from 4" back to 3.5". Again, this is all a judgement call.

_Also , you mentioned soil test in spring in order to prep soil and give it what it needs for fall overseed. Does this mean taking soil sample now in summer is too late to get the soil to where it needs to be at time of overseed (because it takes a while to prime and get the soil right)?_ It's never "too late" to get a soil test done. One of the biggest issues of being late is the pH. If your pH is low, you need to apply lime which can take some time to work it's way into the soil. Applying lime just before seeding can cause extremely high pH levels in the upper layer of soil where the roots of the seedlings will be. It's best to apply lime 6 months or so prior to seeding. You also don't want to be applying a bunch of different stuff all at one time. A lot will be determined by the results of the soil test. If things are way off and require a lot of adjustment it's best to do it in smaller amounts over time. Of course, if the test results are pretty good and you don't need to make a lot of adjustments you can do it closer to time of seeding.

Again, a lot of this is seat of the pants with some judgment thrown in. The more you do it the better you will be. Always be ready to make adjustments to any "plan" due to unforeseen circumstances. Mother nature can be brutal and unpredictable so have a plan but also be very flexible and reactive to different situations. Hope this helps.


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## Bkell101 (Jun 25, 2018)

@ForsheeMS this is so helpful. Thank you!


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## Olkutty (Jul 12, 2019)

Sorry to dig up an old thread, but there is definitely some pertinent information in it. I'm just shy of 2 weeks from a lawn reno/over seed/top dress per se', and I'm looking for information on the best fertilizer to use. But before I ask that, I have a question regarding all the procedures I've come across during the over seed. if I'm doing a top dress, (heavier in some areas due to complete washout against the house), wouldn't it be best to power rake, aerate, seed, then top dress? (Heavier areas of compost/soil would get sewn after however.) That way the seed is covered by the medium? Just curious why no one every mentions this, even on the 1,000 YouTube vids I've watched on topdressing.

Second, the fertilizer. I read here that a 0-25-25 would be best until the germination is complete, then a dose of N would be a good idea. Could someone please elaborate more on how to achieve this by making your own from a local farm store? Thanks in advance!


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