# When is last fall fert app?



## jeffman2 (Apr 8, 2019)

I live in Massachusetts and have been doing weekly urea applications of .25N. My question for any fellow northeastern folks out there is when do you normally stop throwing down fert? I am definitely doing one more app on Oct 18th but I'm thinking I should be throwing down a couple more times after that....thoughts?


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## badtlc (Aug 22, 2019)

I think the rule of thumb is no nitrogen when temps fall below daytime highs of 60F.


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## Scagfreedom48z+ (Oct 6, 2018)

I spray .30 lbs of dissolves urea weekly until top growth stops and grass clippings become reduced


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## NJ-lawn (Jun 25, 2018)

I usually stop spoon feeding at average first frost date. Pause til top growth stops, then winterizer


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## jeffman2 (Apr 8, 2019)

NJ-lawn said:


> I usually stop spoon feeding at average first frost date. Pause til top growth stops, then winterizer


Thanks! What do you do to winterize?


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## NJ-lawn (Jun 25, 2018)

One lb. fast release N/1M


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## ken-n-nancy (Jul 25, 2017)

jeffman2 said:


> I live in Massachusetts and have been doing weekly urea applications of .25N. My question for any fellow northeastern folks out there is when do you normally stop throwing down fert? I am definitely doing one more app on Oct 18th but I'm thinking I should be throwing down a couple more times after that....thoughts?


The short answer is that there are a variety of approaches to late fall fertilization for cool season grasses, so different people on the site have chosen different approaches. There really isn't consensus as to which approaches are best, partly due to the fact that different approaches may be best for different grass types and local climate, and there is a fair bit of variation as to what works best depending upon the conditions that end up happening in the late fall, winter, and early spring.

If you haven't already, you need to read the article, Fall Nitrogen Blitz (Cool Season Grasses Only).

What I do, personally, is apply only quick-release fertilizers in the mid- to late-fall, starting about 2-3 weeks before *average* first frost. (Note that it is the *average* first frost that matters in this case, not when the actual first frost happens, which has significant variation that isn't well correlated with seasonal trends.)

I then make my last quick-release fertilizer application about 4 weeks (1 month) _before_ I expect top growth of the grass to stop. If you don't know when the top growth of your grass will stop (which varies a lot by location, amount of sun, grass type, etc.) then a relatively safe way to approximate the date that top growth of your grass will stop is to presume that it is about 4-6 weeks after your *average* first frost. This means that your last quick-release fertilizer application will be about the time of your average first frost to about 2 weeks later than that.

To find your average first frost, you can use this website: Dave's Garden Freeze / Frost Dates by Zip Code. Look for the "Fall 32°" date at 50% at the location which is closest to your house (multiple sites will be listed after you do the lookup).

My personal planned date for last fertilizer application given the history in our lawn is around Oct 15-20. I'm about 50 miles north of you, depending upon specifically where you are in metro Boston. You can probably get away with one week longer, particularly if you are right on the seacoast, where temperatures are moderated a bit.


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## MJR12284 (Jun 21, 2020)

@ken-n-nancy Thank you. This is very helpful. Does this same logic apply to Fall renos as well? My seed down date was Aug 30 and I just did my 3rd spoon feeding this past weekend. Looks like my average frost date is Oct 10-20.


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## ken-n-nancy (Jul 25, 2017)

MJR12284 said:


> @ken-n-nancy Thank you. This is very helpful. Does this same logic apply to Fall renos as well? My seed down date was Aug 30 and I just did my 3rd spoon feeding this past weekend. Looks like my average frost date is Oct 10-20.


I don't have any experience with TTTF. I know that KBG is very hungry in its first year, so I tend to err on the aggressive side for first-year fertilization of KBG. For safety with new grass, you should apply the "last fertilizer" earlier, to allow more time for hardening off. To be aggressive with growth, you can fertilize later, but that increases the risk of going into winter too lush. TTTF isn't quite as winter-hardy as KBG, so ending sooner (around the time of average first frost) may be prudent.

When does grass tend to stop growing for you? Is it usually still growing after Thanksgiving?


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## Green (Dec 24, 2017)

ken-n-nancy said:


> This means that your last quick-release fertilizer application will be about the time of your average first frost to about 2 weeks later than that.


The average first frost date doesn't work for all areas. When I use that, the grass tends to be Nitrogen deficient in November, and any rust disease gets really bad.

That notwithstanding, I'm playing with a new method this year that uses a mix of ammonium sulfate, fast release urea, and medium/long range slow release urea about 2 weeks after average first frost date, and no winterizer after growth stops. It will be the first year trying this. I also did/am doing a Fall blitz this year (mostly using Carbon-X) due to rust disease. Due to the blitz, my grass is finally getting to the point where it no longer looks Nitrogen deficient (as it did coming out of Summer). I think it's starting to outgrow the disease. The Summer really took a lot out of it, and lack of fertilizer during Summer really did not help things. I think that's why it was so prone to rust. Next year, an early August organic fert app would also be a good idea.

The medium length slow release compnonent I'm using (for years now) is methylene urea. The long-term component in my mix for the final app (something new to me that I'm trying in the program this year) is Nitroform (urea formaldehyde).


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## ken-n-nancy (Jul 25, 2017)

Green said:


> ken-n-nancy said:
> 
> 
> > This means that your last quick-release fertilizer application will be about the time of your average first frost to about 2 weeks later than that.
> ...


Yeah, I had been using "average first frost" as the marker for my "last fertilizer" for a number of years, but found that my growth stoppage wasn't 1 month after that, but more like 8 weeks later. (Just shy of two months.) The specific dates for me are Sept 26 for "average first frost" and as indicated by my log book over the past 6 years, Nov 14-18 for the shady back and side lawns, and Nov 20-26 for the sunnier front lawn, which is a range from 7-9 weeks.

I'm concerned though, that in some more southern locations (say southern Pennsylvania / northern Maryland) that they don't get 7-9 weeks of grass growth after "average first frost." For example, Philadelphia has an "average first frost" of Oct 25. Does top growth normally continue until around Christmas Day (two months later) in southeastern PA?

(If so, two months may be a better figure to use, which would indicate that maybe fall fertilization should continue until a month after average first frost...)



Green said:


> That notwithstanding, I'm playing with a new method this year that uses a mix of ammonium sulfate, fast release urea, and medium/long range slow release urea about 2 weeks after average first frost date, and no winterizer after growth stops. It will be the first year trying this.


Interested to hear how it goes. Last year, I skipped the final "after growth stoppage" fertilizer application because I was concerned that making that final application was increasing the amount of snow mold I would get. This last year the grass did well through the winter and then in the spring, too. However, that could have been nearly entirely due to the comparatively mild winter vs. what we usually get.



Green said:


> I also did/am doing a Fall blitz this year (mostly using Carbon-X) due to rust disease. Due to the blitz, my grass is finally getting to the point where it no longer looks Nitrogen deficient (as it did coming out of Summer). I think it's starting to outgrow the disease. The Summer really took a lot out of it, and lack of fertilizer during Summer really did not help things. I think that's why it was so prone to rust.


We've never had rust in our lawn before -- until this year. This September, I was mowing the lawn and couldn't figure out why the front of the mower had turned orange. I'm not sure what specifically has made it go away -- fall fertilization, cooler temps, very dry weather, or what, but the grass seems to have fully recovered and the mower doesn't end up looking orange any more...


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## Dan1234 (Aug 31, 2018)

Hi @ken-n-nancy ,

Southeast PA here. that's a good point on how long the top growth continues in different regions. It is definitely stopped by christmas, minus the one weird warm december we had about 5 years ago. I would say most time mowings are wrapping up somewhere around the Thanksgiving time, with minor variances year to year.


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## doverosx (Aug 7, 2019)

I throw down until I don't get any growth in 7 days. If there is "exess" N, the plant will ignore it since the plant determines what nutrients are consumed.


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## Powhatan (Dec 15, 2017)

I've noticed in my area after first freeze that still have top growth for another three weeks, so right after first freeze I broadcast a final fert majority fast release granular.


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## Green (Dec 24, 2017)

@ken-n-nancy

I agree with everything in your long post above with replies to mine in it.

In talking with a pro in this area a while back, he suggested a final app about a week before Halloween. Back then, I was doing the avg first first guideline and was a relative newbie, so I was skeptical you could fertilize that late in my area. Average first frost is sometime between Oct. 10th and 22nd, or more accurately, Oct. 16th. But now as the years have gone on, I'm seeing he was probably about right. He also agreed with my idea of using the methylene urea when I ran into him about 2 years ago in a store and mentioned what I was buying and why.

The latest last mow here one year, 2015, I think, was around Christmas, but that was an outlier in a warm Fall/early Winter year, and not a ton was cut off.

What I might do this year, is create a test area that gets treated using my conventional method (after growth winterizing app using Green Max, like I've done every year the past few), and then go all-in almost everywhere else with my experimental method (final app prior to Halloween, using a more methylene-urea-heavy blend). Very simple experiment.

Last year's comprehensive winterizing experiment was a great idea in theory, but failed due to flooding and Poa Triv infestation. Not a good location for the test. Unfortunately, that area is out of commission this year for the same reason plus an overseed. And it was just too complicated.

Another thing, other than snow mold, that concerns me, is that my Poa Triv always seemed to respond really well to the late November or early December post-growth app. It seemed to dominate the lawn in some areas and go crazy until early January after that app was applied every year. If moving up the app a month helps prevent that, I'm all for it. Triv is more cold tolerant than KBG, so it makes sense a later fertilizer app might favor it over KBG (not to mention Rye/Fescue).

The app will likely be somewhere between Oct 24th and 31st. The problem is, the later it gets, the less N uptake there is due to reduced ET. From Oct. 1 to Oct. 31, ET drops drastically, I believe. It's going to be a balancing act. It really needs to take place before the trees go dormant, I think. And there's the whole issue of pushing growth too late as well. Because of these issues, I really feel that November should be a zero or at least minimal fertilizer month...no Potassium due to snow mold, no Phosphorus due to certain other diseases, aiding Poa, and potential pollution, and no N except for very low rate spray apps (e.g. FAS).


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## MDJoe (Sep 16, 2019)

ken-n-nancy said:


> Yeah, I had been using "average first frost" as the marker for my "last fertilizer" for a number of years, but found that my growth stoppage wasn't 1 month after that, but more like 8 weeks later. (Just shy of two months.) The specific dates for me are Sept 26 for "average first frost" and as indicated by my log book over the past 6 years, Nov 14-18 for the shady back and side lawns, and Nov 20-26 for the sunnier front lawn, which is a range from 7-9 weeks.
> 
> I'm concerned though, that in some more southern locations (say southern Pennsylvania / northern Maryland) that they don't get 7-9 weeks of grass growth after "average first frost." For example, Philadelphia has an "average first frost" of Oct 25. Does top growth normally continue until around Christmas Day (two months later) in southeastern PA?
> 
> (If so, two months may be a better figure to use, which would indicate that maybe fall fertilization should continue until a month after average first frost...)


Well, I am in central Maryland. Similar climate to Philly (I'm further south, but more inland and rural). My average first frost is also around 10/25, but my last mowing is mid-November, typically. It can stay pretty green until January though many years.

There's "frost" then there's a FREEZE. We may hit 32 in late October, but our first hard freeze (that kills most annual/deciduous vegetation, say under 25 degrees) isn't usually until around Thanksgiving.


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## Lawn Noobie (Sep 29, 2020)

@MDJoe so when do you normally apply your last application of fertilizer and what do you put down? Just curious if I am on the right path and I am in the same region as you are


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## PrisizhuhnRedNek (Sep 30, 2020)

@MDJoe @Lawn Noobie

I'm in eastern panhandle of WV, so fairly close to you guys. My plan has been to stop N app's somewhere around 50 soil temps or around first week of November. I was not into lawn care as much last year but I believe I was still mowing into mid November.
It looks like this coming Friday, the weekend and into beginning of next week, a good frost might be on it's way. nice rain thur-fri though, then as the system passes, cooler air is going to funnel in.


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## GrassOnTheHills (Jul 3, 2020)

Since I don't see it mentioned here, Ryan Knorr's last two videos talk specifically about this. The one with "FINAL RESULTS" in the title has a little chat about the "old school" way of thinking of dumping a good bit of N late in the season to help with Spring green-up, and how that was found to be very inefficient (to the tune of like 88% N lost), and it goes into a bit of detail of the new way of doing things. I honestly haven't watched the winterizer video yet (his most recent upload), but it's got winterizer right in the title so I'm sure it's applicable here.


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## always_creative (Aug 28, 2020)

GrassOnTheHills said:


> Since I don't see it mentioned here, Ryan Knorr's last two videos talk specifically about this. The one with "FINAL RESULTS" in the title has a little chat about the "old school" way of thinking of dumping a good bit of N late in the season to help with Spring green-up, and how that was found to be very inefficient (to the tune of like 88% N lost), and it goes into a bit of detail of the new way of doing things. I honestly haven't watched the winterizer video yet (his most recent upload), but it's got winterizer right in the title so I'm sure it's applicable here.


That was an excellent video. If anyone is interested in the research links, these are in the footnotes.

Winterizer Studies 
https://journals.ashs.org/hortsci/view/journals/hortsci/46/11/article-p1545.xml
https://www.golfdom.com/rethinking-fall-soluble-nitrogen-fertilization-of-cool-season-grasses/
https://turf.unl.edu/turfinfo/Fall%20Fertilization.pdf

Others who are much more experienced can correct me if I misunderstood, but the cliff notes is: Bulk of the N in September, do a long taper into the colder months rather than a big dump of N later, and extra potassium doesn't have much value for winterizing cool season grasses.


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## badtlc (Aug 22, 2019)

GrassOnTheHills said:


> Since I don't see it mentioned here, Ryan Knorr's last two videos talk specifically about this. The one with "FINAL RESULTS" in the title has a little chat about the "old school" way of thinking of dumping a good bit of N late in the season to help with Spring green-up, and how that was found to be very inefficient (to the tune of like 88% N lost), and it goes into a bit of detail of the new way of doing things. I honestly haven't watched the winterizer video yet (his most recent upload), but it's got winterizer right in the title so I'm sure it's applicable here.


No discussion of P or K for winterizing was a bit disappointing.


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## Harts (May 14, 2018)

always_creative said:


> GrassOnTheHills said:
> 
> 
> > Since I don't see it mentioned here, Ryan Knorr's last two videos talk specifically about this. The one with "FINAL RESULTS" in the title has a little chat about the "old school" way of thinking of dumping a good bit of N late in the season to help with Spring green-up, and how that was found to be very inefficient (to the tune of like 88% N lost), and it goes into a bit of detail of the new way of doing things. I honestly haven't watched the winterizer video yet (his most recent upload), but it's got winterizer right in the title so I'm sure it's applicable here.
> ...


Your summary is pretty good. How late you go into the season is going to be climate dependent - folks in the Northeast and Canada will likely only go into the first or second week of October. The further south you go, you can continue to drop N a few weeks later. Beyond this, I don't see the value in adding more N. I read some members wanting to time a Winterizer app in order to give them a head start in the Spring. My advice would be to just feed your lawn in the early Spring to jump start it.

Late season potassium (read: after Labour day) can have a negative impact on cool season grasses that get extended snow cover - in excess of 2-3 straight months. Excess K can lead to increased risk of snow mold in the Spring. If you watch one of Connor's videos from this past Spring (I think it was this year) he had a ton of it.


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