Average First Frost Date vs Real First Frost Date

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andy10917
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Average First Frost Date vs Real First Frost Date

Post by andy10917 » October 30th, 2022, 11:00 am

As the author of the Fall Nitrogen Regimens thread, I spend a fair amount of time studying year-to-year variances and how I might improve the checkpoints we use to make the regimen work better.

One of the most frustrating, repeating questions I see each year is related to whether to use the (recommended) Average First Frost Date or the date of the first actual frost date. This year provided a scenario that I studied in detail, and it backs up the importance of using the Average First Frost Date to time applications and "the Pause".

Where I live, the documented Average First Frost Date is October 15 - October 17. The Actual First Frost Date this year was October 30th. That's a two week difference. Which of the dates did the slowing of growth follow? It turns out that slowing growth followed the Average First Frost Date, and the progress has been steady since then - it did not wait for an actual frost.

Going through my data for 10 years, neither early actual nor late actual frosts affected the slowing of growth, with the exception of Zoysia observed on my neighbor's yard. Even Crabgrass declined more than inline with Average First Frost Date than Actual First Frost Date.

My conclusion is that Average First Frost Date is a much better indicator to use. This is likely to be due to the fact that Average First Frost Date includes the effects of the length of day, strength of the sunshine, rainfall patterns, etc. Actual Frost does not seem to be much of a factor unless you are growing Zoysia in the North. Average First Frost Date is climatological and actual frost is not.

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Re: Average First Frost Date vs Real First Frost Date

Post by turf_toes » October 30th, 2022, 2:32 pm

^^^

This

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Re: Average First Frost Date vs Real First Frost Date

Post by Green » October 30th, 2022, 10:52 pm

Growth started to slow here (in all except the habitually most lagging lawn area of my yard) over the past week or so. Like clockwork, this was, once again, about 2 weeks after my average first frost date (which itself is Oct. 15-18). This means my yard is entering the pause period right about as predicted. One more 0.25 lb urea drop on that lagging area, and that's it until the end of the pause. As predicted, I'm once again fertilizing almost until Halloween. Everything is happening within one week or tighter of my predictions. Growth should stop in just over 4 weeks or so. I feel like I have a really good handle on this now, after ten years.

I was torn about whether to push one more 0.2 lb N app from AMS on my "leading area" (which stops growing the earliest and probably will in 2-3 weeks), but I've pretty much decided against it. I have new grass there and only got a half to 3/4 lb of N on there (from urea) so far, but I know probably shouldn't push it...I can pick up again in the Spring.

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Re: Average First Frost Date vs Real First Frost Date

Post by bpgreen » October 31st, 2022, 1:44 am

I'm going to go out on a limb and make a prediction.

This post will have no effect on questions about average vs actual first frost in the other thread

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Re: Average First Frost Date vs Real First Frost Date

Post by andy10917 » October 31st, 2022, 8:33 am

I know, but it makes me feel better :banghead: :banghead: :banghead:


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Re: Average First Frost Date vs Real First Frost Date

Post by ronfitch » October 31st, 2022, 11:29 am

andy10917 wrote:
October 30th, 2022, 11:00 am
As the author of the Fall Nitrogen Regimens thread, I spend a fair amount of time studying year-to-year variances and how I might improve the checkpoints we use to make the regimen work better.

One of the most frustrating, repeating questions I see each year is related to whether to use the (recommended) Average First Frost Date or the date of the first actual frost date. This year provided a scenario that I studied in detail, and it backs up the importance of using the Average First Frost Date to time applications and "the Pause".

Where I live, the documented Average First Frost Date is October 15 - October 17. The Actual First Frost Date this year was October 30th. That's a two week difference. Which of the dates did the slowing of growth follow? It turns out that slowing growth followed the Average First Frost Date, and the progress has been steady since then - it did not wait for an actual frost.

Going through my data for 10 years, neither early actual nor late actual frosts affected the slowing of growth, with the exception of Zoysia observed on my neighbor's yard. Even Crabgrass declined more than inline with Average First Frost Date than Actual First Frost Date.

My conclusion is that Average First Frost Date is a much better indicator to use. This is likely to be due to the fact that Average First Frost Date includes the effects of the length of day, strength of the sunshine, rainfall patterns, etc. Actual Frost does not seem to be much of a factor unless you are growing Zoysia in the North. Average First Frost Date is climatological and actual frost is not.
We need a "Like" button on this forum. Thanks, Andy. For everything.

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Re: Average First Frost Date vs Real First Frost Date

Post by pristinegreen75 » November 1st, 2022, 5:01 pm

Going to be awhile here before first frost. still cutting every 3 days

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Re: Average First Frost Date vs Real First Frost Date

Post by andy10917 » November 1st, 2022, 6:46 pm

When did you stop fertilizing applications?

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Re: Average First Frost Date vs Real First Frost Date

Post by PSU4ME » November 2nd, 2022, 12:53 pm

I definitely noticed my grass slow it’s growth around Oct 15-20 and my AFFD is 10/14 so there is another data point for ya. Last fert was first week in October so things are progressing nicely.

My only issue is really determining when it actually stops, I feel like it’s been post thanksgiving the last few years, almost into Dec which makes it hard to keep the sprinklers active for that long.

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Re: Average First Frost Date vs Real First Frost Date

Post by Green » November 3rd, 2022, 2:38 am

One thing you can do to tell if it stopped growing is pick an area to use as a test that requires a couple of mower passes, and mow it at the same HOC setting in the same direction each time to test for growth, with the bag on the mower (a push mower works best for this). If you have more than a few random pieces of grass in the bag (that didn't get cut the last time and popped up the next time), it means it grew since the previous mow. You will also likely see the clippings get progressively shorter over time if you keep the same test mow interval. Once you've determined it didn't grow, it's best to apply that fertilizer in a timely fashion so as not to allow soil temperatures to decline excessively. You may have different timings in different areas of your yard, and therefore might want to use several test areas. You might even choose (like me) to apply your winterizing application on each area as it stops growing rather than waiting for all areas to stop. Depends on how complex your yard layout, shape, and microclimates are and how dedicated you want to be. With urea, there is a small amount of wiggle room due to slower hydrolysis in cool Fall weather (I know Morph has mentioned this too, and is ok with being a tiny bit early...e.g. you think it stopped growing but aren't sure all lawn areas are synced totally). With ammonium sulfate, timing leeway on the early side is practically nil as it's already plant-available. Supposedly there is roughly a two week period after growth stops where it's receptive. But I personally prefer to get it down ASAP before soil temps tank. (If you wait too long, you're not winterizing but are dormant feeding, which is a controversial practice for environmental reasons).

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Re: Average First Frost Date vs Real First Frost Date

Post by edslawn » November 3rd, 2022, 9:15 am

Thanks for the reminder Andy!

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Re: Average First Frost Date vs Real First Frost Date

Post by pristinegreen75 » November 3rd, 2022, 4:03 pm

I mulch everything but I threw the bag on today and definitely getting clippings in it. I compared cut and uncut strips side by side. Not much difference. looks like I won't have to cut for maybe another 2-3 days which will be 5-6 days since last cut. Last fert was Oct 11. Man that took awhile.

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Re: Average First Frost Date vs Real First Frost Date

Post by ronfitch » November 5th, 2022, 11:31 am

Here is another data point, Andy.

My AFFD is Oct. 5th. This year, real date was Oct. 14th. My last fertilization was Sept. 28th.

Our lawn started to dramatically slow just before the real first frost, despite the 4” soil temp never dropping into the 30s yet (dropped into the mid-40s for a few days in late October but up to low 50s for a few days late October/early November and is back up to just above 45 on November 4th). I plan to mow again on November 5th, mostly to mulch leaves but also to see if there are clippings. Forecast is for rain later in the week, perhaps first snow of the season by the 11th.

This might be of some interest. Scroll down to “ Climate change is shifting the averages” section - in the Twin Cities, the growing season is 33 days longer in 2022 than it was in 1970 and we have 15 fewer nights below 32 degrees F:

https://www.mprnews.org/story/2022/10/0 ... win-cities

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Re: Average First Frost Date vs Real First Frost Date

Post by andy10917 » November 6th, 2022, 9:55 am

I agree. The use of both the AFFD -and- the stoppage of growth date creates a double-check on the regimen, and there is evidence the the length of The Pause is increasing. As long as you use the actual data for the stoppage of growth (instead of a calendar calculation), you should be good. Calendars are useful as a mulch//compost source and little more - people that try to figure the dates back at the beginning of the season get what they deserve.

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Re: Average First Frost Date vs Real First Frost Date

Post by ronfitch » November 6th, 2022, 8:57 pm

ronfitch wrote:
November 5th, 2022, 11:31 am
Here is another data point, Andy.

My AFFD is Oct. 5th. This year, real date was Oct. 14th. My last fertilization was Sept. 28th.

Our lawn started to dramatically slow just before the real first frost, despite the 4” soil temp never dropping into the 30s yet (dropped into the mid-40s for a few days in late October but up to low 50s for a few days late October/early November and is back up to just above 45 on November 4th). I plan to mow again on November 5th, mostly to mulch leaves but also to see if there are clippings. Forecast is for rain later in the week, perhaps first snow of the season by the 11th.

This might be of some interest. Scroll down to “ Climate change is shifting the averages” section - in the Twin Cities, the growing season is 33 days longer in 2022 than it was in 1970 and we have 15 fewer nights below 32 degrees F:

https://www.mprnews.org/story/2022/10/0 ... win-cities
Mowed today. No clippings in a few spots, maybe to 1/4” inch in the rest. I last mowed seven days earlier. It has definitely slowed but areas grew over the past week. So, until next week …

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Re: Average First Frost Date vs Real First Frost Date

Post by Green » November 6th, 2022, 9:31 pm

My pause has been starting about 10-15 days after my average first frost date since I've been doing lawn care...10 years now. It has been pretty darn onsistent for that period of time.

The only change has been me extending Fall Nitrogen applications by a week or two after learning that I didn't need a 6-8 week pause and grass that stated looking nutrient deficient at the end of that.

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Re: Average First Frost Date vs Real First Frost Date

Post by Dwinter » November 15th, 2022, 11:54 am

1st frost this morning. 12days late .

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Re: Average First Frost Date vs Real First Frost Date

Post by Green » November 16th, 2022, 2:22 am

It was a 3.5 week pause for me this year on the first areas that were winterized (yesterday). Shortest ever for me. As a result, they did not start looking Nitrogen deficient this year. Looks like it will be a 4.5 to 5 week pause on some of the other areas that haven't been Winterized yet.

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