# Tall Fescue - Does it or does it not go dormant in the heat of summer?



## Deadlawn (Sep 8, 2020)

I have read here on this site that while tall fescue is a heat and drought tolerant turf grass because of deep roots, when the roots finally run out of water, it doesn't have the ability to go dormant like ***, so will just die. But here on the Maryland Extension page, they state that tall fescue does indeed go dormant:

https://extension.umd.edu/resource/organic-lawn-care

From the article:

"Established tall-fescue lawns can go dormant during the summer and very rarely need to be watered."


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## Powhatan (Dec 15, 2017)

Honestly, I don't believe you can answer this with a yes or no, it's more of it depends on the situation. One minor example: fescue cut short is not going to be as drought tolerant as fescue allowed to grow tall.

I don't irrigate and typically my majority fescue grass does get brown in some areas during July, then a few weeks later after some rain, the grass greens back up. Does that mean the fescue went dormant, don't know. I'm sure some % of fescue dies. Since I've been improving my soil and broadcasting more organic fert than synthetic, the grass has held greener longer during the summer heat and drought.


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## Deadlawn (Sep 8, 2020)

Thanks for your input, @Powhatan . This sort of makes sense with any grass. There were a few people on this site who claim that *** could go dormant more easily even though it didn't have the deep roots that tall fescue does.

I had much better success with newly seeded areas this past year than in previous years. Besides not having a severe drought in 2021, I made sure to water deeply if we didn't get at least an inch of rain a week. A three week vacation in August caused a few areas to brown out and even die in small areas, but I would concluded that 2021 was mostly a success for my Fall 2020 seeded areas.

I tried something new this year. In late August 2021 a seeded a large area that nothing succeeded in before. But this time I tilled the area down to about a foot, then spread 2-3 inches of compost on top, spread some organic starter fertilizer, seeded and rolled the area. The area next to it I did everything the same except I did not till that area. The difference was very noticeable. The tilled area jumped out of the ground while the untilled area was much slower to get started. The most startling difference was that the clover I mixed into the grass seed did well in the tilled area, but turned yellow and died in the untilled area. The grass in the untilled area has now caught up and you can't really tell a difference, but I have to speculate the root development is probably much better in the grass that got a faster start at the beginning and will probably have a much better chance at surviving Summer 2022.


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## stevehollx (Apr 8, 2020)

Someone once said that KBG can go brown and dormant and recover, but when fescue transitions to brown it is dead. So I tend ti think that fescue dormancy is less resilient and a short period when it halts growth and turns dull/grey but will turn brown and die without a water after 2-3 weeks in heat of summer.


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## Deadlawn (Sep 8, 2020)

stevehollx said:


> Someone once said that KBG can go brown and dormant and recover, but when fescue transitions to brown it is dead. So I tend ti think that fescue dormancy is less resilient and a short period when it halts growth and turns dull/grey but will turn brown and die without a water after 2-3 weeks in heat of summer.


Others here have said and posted that too. Yet I have never seen it in any publications or on a cooperate extension website.

But it's on the internet, so it must be true! :roll:


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## g-man (Jun 15, 2017)

All you need to do is search in the univ websites. Here are two:



> Species: Tall fescue is one of the last to show drought symptoms, many days to weeks following bluegrass or perennial ryegrass. Since dormancy is a survival mechanism, Kentucky bluegrass and perennial ryegrass tend to survive drought better. (Actually Dr. Yiwei Jiang here at Purdue is trying to understand why cultivars respond differently to drought)


-Dr. Zac Reicher https://turf.purdue.edu/drought-affects-all-turf-areas-differently/



> This deep root system allows tall fescue to stay green longer in drought than other coolseason grasses like Kentucky bluegrass. However, tall fescue has minimal drought survival if extended drought conditions persist to the point of tall fescue leaves turning fully brown or dormant.


-UNL - https://turf.unl.edu/NebGuides/Grassesforlawns2012k.pdf


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## Green (Dec 24, 2017)

As posted above, do lots of reading on this topic.

The bottom line though is this: all species have a tradeoff between drought avoidance (staying green before dormancy) and drought tolerance (extent of dormancy and survival without water).

KBG is a grass that undergoes complete dormancy, but has only fair to good drought avoidance.

The types of Tall Fescue used for turfgrass cultivar breeding are great at avoidance, but only fair at tolerance. This is known as incomplete dormancy. It plays out like this: the plant needs to maintain at least some green cover during dormancy, and its growth slows or stops.

Additionally, it still needs more water during dormant periods than grass types that undergo complete dormancy (those that can turn fully straw brown and still, survive).

There is no turfgrass currently in use that does both things equally well.

In terms of performance, it's probably a wash in mild drought periods between KBG and TTTF. In prolonged drought going on for weeks or months, KBG would have an edge.

The difference might be due to rhizome expression. TTTF has few rhizomes but more aggressive topgrowth and roots; KBG the opposite. Some providers of more rhizomatous TTTF claim that their varieties do better at drought tolerance, but I'm not sure this is an accepted concept yet, as it might not be enough of an improvement over the average TTTF.


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## MacLawn (Oct 26, 2021)

First off Im no expert, I have been over seeding with what ever Im told is the most draught tolerant TF variety available at the time.
Does TF go dormant in the summer?
Well as plant science goes….I have no idea but generally I dont have to mow my grass past july 4th straight through until the rains return in sept. 
This year with all the rain I was mowing 3x a week from mid may until mid nov.
I dont irrigated and secondary watering is needed just when the water ban hits so my lawn takes beating in the hot dry months. 
Here is what my lawn will often look like in the dryer years the "line" of brown to green is where the tree line protects the grass from the sun more. As bad as this was it recovered to about 80% before over seeding . 
Everyone always thinks my lawn is dead. Until the cooler/wetter weather comes and im back to mowing multiple times a week.
This year was a rough year on my lawn , Bugs, fungi, yard work and I had a "refreshing" of the lawn and its doing very well now


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## Deadlawn (Sep 8, 2020)

g-man said:


> All you need to do is search in the univ websites. Here are two:
> 
> 
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> ...


Thanks for the links, @g-man . Interesting info. So it appears that tall fescue's survivability rests on how deep down it can penetrate roots into the subsoil. I would think that as some point of bone dryness, KBG would perish as well, though being a rhizomatous grass, will repair bare spots easier. The downside to this is that KBG is more likely to invade garden beds. I could always use the neighbor's KBG stand as the proverbial canary in the coal mine to determine when watering my tall fescue is necessary, LOL!


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## Green (Dec 24, 2017)

According to another source I read a while back, PR is even worse than TF at dormancy, and also worse at avoidance...not to mention more cold susceptible as well...making it by far the least drought tolerant and extreme temperature tolerant turfgrass (yes, even worse than FF, too). Maybe cultivars vary widely or something.

I've not had any real survival issue with PR or TF in established mixes, personally. But I do water even my low input lawn area at least once in a while when needed...several times over the Summer.


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## Green (Dec 24, 2017)

@MacLawn, is the recovery photo before overseeding?

That July-Sept period you described withiut mowing is dormancy. But it has to maintain some green to survive. Once it goes fully brown, it may not. Same with PR. Fine Fescue does a bit better, but still not necessarily great (neighbor's FF/KBG mix went mostly brown one Summer and eventually recovered).


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## Deadlawn (Sep 8, 2020)

Green said:


> According to another source I read a while back, PR is even worse than TF at dormancy, and also worse at avoidance...not to mention more cold susceptible as well...making it by far the least drought tolerant and extreme temperature tolerant turfgrass (yes, even worse than FF, too). Maybe cultivars vary widely or something.
> 
> I've not had any real survival issue with PR or TF in established mixes, personally. But I do water even my low input lawn area at least once in a while when needed...several times over the Summer.


I haven't found PRG to be good for anything except if I really need quick germination. It pretty much does everything else poorly. It's telling that it seems to be in all those mixes that are sold in bulk.


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## Green (Dec 24, 2017)

Deadlawn said:


> Green said:
> 
> 
> > According to another source I read a while back, PR is even worse than TF at dormancy, and also worse at avoidance...not to mention more cold susceptible as well...making it by far the least drought tolerant and extreme temperature tolerant turfgrass (yes, even worse than FF, too). Maybe cultivars vary widely or something.
> ...


Pretty much sums it up. I use it as a supplement for those reasons. Actually does pretty well in mixes, though. Probably lose some in Winter or Summer, though. But I only buy premium cultivars of it.


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## Retromower (Jan 28, 2021)

Just like any other cool season grass, TF will go dormant in the heat of summer. I would say though that TF typically has roots the go deeper (assuming you dont keep it cut short) and will tolorate the heat of summer better because it is more able to dig deep enough to where it can still access moisture.


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## Green (Dec 24, 2017)

Retromower said:


> Just like any other cool season grass, TF will go dormant in the heat of summer. I would say though that TF typically has roots the go deeper (assuming you dont keep it cut short) and will tolorate the heat of summer better because it is more able to dig deep enough to where it can still access moisture.


Yes, but the points made above are that dormancy looks a bit different than with KBG. TTTF likely has to keep a bit of green on it down near the crown throughout dormancy to survive. In order to do so, it may need more frequent watering of 1/4 inch or so than KBG. Probably depends how deep the roots are. During this time, roots likely slough back. I think of it as analogous to TTTF mowed very low (greens heights), which also reduces green material. It doesn't like that, but can survive for a while if conditions are good enough. Regardless, deficit irrigation is a viable strategy with TTTF...especially if soil moisture is in danger of being fully depleted even down deep.

Perennial ryegrass is worse. Fine fescues tend toward slightly more drought tolerant once dormant than TF, but still not anywhere near as good as KBG for most of them.


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## Deadlawn (Sep 8, 2020)

Green said:


> Yes, but the points made above are that dormancy looks a bit different than with KBG. TTTF likely has to keep a bit of green on it down near the crown throughout dormancy to survive. In order to do so, it may need more frequent watering of 1/4 inch or so than KBG. *Probably depends how deep the roots are. *During this time, roots likely slough back. I think of it as analogous to TTTF mowed very low (greens heights), which also reduces green material. It doesn't like that, but can survive for a while if conditions are good enough. Regardless, deficit irrigation is a viable strategy with TTTF...especially if soil moisture is in danger of being fully depleted even down deep.
> 
> Perennial ryegrass is worse. Fine fescues tend toward slightly more drought tolerant once dormant than TF, but still not anywhere near as good as KBG for most of them.


How deep the roots are is the big question. Tall fescue has the ability to send roots much deeper. So in light of this and the fact that no grass can stay dormant if it completely dries out, it's probably a tossup as to which could survive a severe drought. After all, if the ground dries out in an established tall fescue stand down to the bottom of its roots which can extend down over a foot, how long has the root zone of KBG been dry by that time?

I have also read conflicting info on whether tall fescues or fine fescues are more drought tolerant. Not to confuse with heat tolerant which fine fescues are quite poor at. IIRC, fine fescues will usually survive droughts as long as they aren't subjected to full sun. At my old house, I had a large patch of creeping red fescue under a dense maple. It would brown out mid-summer, but always green back up again by mid-Sept.


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## Green (Dec 24, 2017)

@Deadlawn, what you said about KBG versus TF sounds very logical, and I would expect that type of outcome...basically a tossup. The C3 biology ends up being the limiting factor during drought. Both will die. A small amount of KBG might survive severe drought due to rhizomes staying viable, but you'd still have to reseed to have a lawn after.

Then again, that's not likely an issue for us...we get some rain during droughts usually. Out West, different story. Even C4 grass is challenged.

The thing that complicates it, where we both live, are rocks. There are so many rocks everywhere that rooting has to be pretty limited. I'm pretty sure no roots are going to go down 6 feet here. Not only that, but rocks hold heat really well once absorbed, and can fry roots as they keep the soil temps high. Double whammy. Screwdriver test and dig out bad areas is about all you can do.

As far as fine fescue, I think you're mostly right. I think it varies by species and cultivar, too. I've seen fine fescue survive on minimal water when brown for a few weeks, but I've also seen it die in the Summer when it's really dry.


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## Deadlawn (Sep 8, 2020)

Green said:


> @Deadlawn, what you said about KBG versus TF sounds very logical, and I would expect that type of outcome...basically a tossup. The C3 biology ends up being the limiting factor during drought. Both will die. A small amount of KBG might survive severe drought due to rhizomes staying viable, but you'd still have to reseed to have a lawn after.
> 
> Then again, that's not likely an issue for us...we get some rain during droughts usually. Out West, different story. Even C4 grass is challenged.
> 
> ...


Rocks aren't much of a problem here in the valley as they are up in the Berkshires. Here is mostly sand and the problem becomes too much drainage and inability to hold water for very long. Compaction is of course a problem as it is for most. Construction equipment while building a house and then over time, walking and mowers turn soil into hard pan. I can only imagine the problem is worse for people who use heavy riding mowers. Core aerators can help, but really don't go down very deep, so grass roots are still concentrated within a few inches of the surface. We know that tall fescue CAN send roots down deep, but it CANNOT send roots down into hard pan. In those conditions, it's drought advantages are negated.

I think what causes fine fescue to perish most often is the heat of full sun rather than drought.

Could you elaborate on what you mean by C3 and C4?


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## Green (Dec 24, 2017)

@Deadlawn: C4 grasses are warm-season grasses.


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## Deadlawn (Sep 8, 2020)

Green said:


> @Deadlawn: C4 grasses are warm-season grasses.


Got it, thanks! I actually used to have a large part of my lawn zoysia when I lived in NJ. I'm in MA now and I see zoysia lawns which are brown 8 months of the year here. It's a lush carpet when green, but its aggressiveness can be a royal pain.


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## Green (Dec 24, 2017)

Deadlawn said:


> Green said:
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> 
> > @Deadlawn: C4 grasses are warm-season grasses.
> ...


Yeah, I saw a bunch of them on the road today. All brown. Have been for over a month. I have neighbors with a little bit invading cool season grass. They've been killing it off with me helping out at times. Late April to mid Nov seems to be the extent of the Zoysia season here. 6.5 months of actual green...

In central NJ you'd probably get 7.5 months, similar to Coastal Southern NE. Maybe 8 months in coastal South Jersey.


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## Deadlawn (Sep 8, 2020)

Green said:


> Deadlawn said:
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> > Green said:
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Interesting that you're only half a zone different than me, yet zoysia here is only green from mid-May through mid-Sept. I'm in 6A.

I was in Northeast NJ which is Zone 7A. We got about 6 months of green out of the zoysia there.


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## Green (Dec 24, 2017)

Deadlawn said:


> Green said:
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> > Deadlawn said:
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I think the season has extended over time, even the last few years, probably due just as much to the tons of Fall rain as from Zone creep. I don't think anyone would mow Zoysia between early Oct and mid May here, but it has seemed to retain nearly acceptable amounts green beyond those points most years recently. At Thanksgiving, I saw some Zoysia that was still somewhat green. It was in the neighboring yard to my family member in Zone 7a coastal CT (which has the same climate as central Jersey apparently, and is now part of the transition zone by some maps). There was also an Oak tree that was still mostly green two weeks before that at the previous visit. Only 40-60 min away, but pretty different timing from my area. Strangely, the soil temps were slightly lower on that day (not a real cold day) than mine were the following week.

We used to be zone 6a (tethnically called 6 since they pulled the interim map) here, when I was a kid in the 1990s. And we were zone 5 when my parents were kids. We could be 7a before I have kids, or certainly before any kids I would have would go to college.

I'd like to hear from someone older than me...but have a feeling no one mowed cool season much here past mid November 25 years ago where I am. I'm almost always doing my final mow a week or two into December since I've been into lawn care (10 years or so).

Strangely, all that said, December has been trending colder again to a degree...at least part of the month, but it can be sporadic with wild temp swings. This year hasn't been wild yet. Lots of average 40 degree days, and got our first real snow of about an inch today. I'll be mowing on Friday after it melts.


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## moedank (Sep 10, 2019)

Yes, I'm reviving an old thread.

@Green, @g-man and others.

Okay, this always creeps up into conversations like this and leaves some of us scratching our heads. *What is the definition of grass dormancy and when does it begin?* This needs to be defined.

@g-man, you've shared links and mentioned before that tall fescue doesn't have a dormancy mechanism. Below is one of your responses from a prior thread - Any regrets with TTTF

_"Drought survival - US Climate office has different levels of drought. Ryan Knorr is currently sitting in a D3 level. This means that it hasnt rain in a while. Under these conditions, non irrigated lawn will first turn brown, then dormant and then die. *TTTF does not go dormant, it goes from brown to dead.* KBG will survive for a few weeks. If it gets some rain (0.5in) it will survive a few more weeks. Can it survive a D4? hmm not likely unless it gets some rain._​
In this thread you referenced the UNL link that states, _"However, tall fescue has minimal drought survival if extended drought conditions persist to the point of *tall fescue leaves turning fully brown or dormant*."_

So, the mechanisms of dormancy only begin once the grass has turned completely 100% brown? I don't think this is what you mean but is it? What is your definition?

I ask because my TTTF looks and behaves very similarly during the coldest winter months and hottest summer months. Simply, it turns mostly brown and either slows down or completely stops growing. When I think of dormancy, I think of a change in the grass' behavior (physiological processes) to help it survive/conserve energy during periods of prolonged detrimental weather, which seems to be a commonly accepted definition for plant dormancy. I think these survival behaviors initiate in some capacity before the grass has turned completely brown, eg, the top growth slows down when the brutal summer weather arrives. Therefore, TTTF does have a dormancy mechanism? Agree, disagree anyone?

What about winter, does TTTF have the ability to go dormant during winter but not summer? If so, why is that? We just made it through February with several snow storms and sustained well below freezing temperatures. My grass blades are mostly brown but there is definitely some slight green sprinkled throughout. It hasn't grown in over three months. I consider it to be dormant; it's surviving through a negative environmental condition.

@Green, you mentioned incomplete and complete dormancy. Did my winter grass only experience incomplete dormancy since it maintained a little bit of green?

I'm beginning to think we all have different ideas/definitions of what dormancy is (think of different spokes on the same wheel) and it gets confusing when we have these talks. Is it just me?


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## Green (Dec 24, 2017)

@moedank, Winter dormancy is different. Similar but different. There is plenty of moisture in the root zone in Winter, but even when the ground is not frozen but too cold for full plant activity, the plant uses very little...I believe less than in Summer (per ET numbers for cool season grasses).

That said, I have never seen Tall Fescue go fully brown any time of year. Mine is mostly brown right now, but still has some green. So I guess you could call Winter dormancy incomplete (for all cool season grasses) as well....unlike Zoysia or Bermuda, which go fully brown when it's cold.

Also, you answered your own question...dormancy does not mean brown. It means very slow/intermittent periods or fully stopped growth for an extended period. Brown may or may not occur to varying degrees....whether heat-induced Summer dormancy, or cold-indiced Winter dormancy. The brown is caused by stress, not dormancy itself. Dormancy is the reaction. So is the brown. The environmental conditions are the cause or trigger. The biology causes it to shut down top growth. Bottom line: "if it ain't growing, it's dormant...regardless of color and hot versus cold temps."

The difference between KBG/certain fine Fescues versus TF/PR/etc., is how dormancy in Summer drought conditions plays out. Tall Fescue and Ryegrass simply have higher ET (and so higher water needs). Without sufficient water, they will die sooner (and will try to hang onto green color as long as possible). By the time they lose all green, they are almost out of resources and will die soon. KBG goes brown faster in general, and can stay that way for weeks.

Also, drought stress dormancy is a different game than just heat, as well. That's when KBG and warm season grasses shine over stuff like Tall Fescue and Ryegrass. In moderate temps, KBG can probably live for months with almost no additional water. Even without heat, PR/TF will be toast in that situation much sooner. But all grass types will eventually slow or shut down (photosynthesis) in either drought or heat, or both. And this is defined as dormancy, is my understanding of the word. It's a reallocation of internal processes, a slowing, and a lowering of performance under severe stress.

There is some speculation that TTTF types with more rhizomes behave more like KBG...better dormancy performance and less death. The rhizomes can store water if the plant goes brown in KBG. But the Fescues, even if they can perform at that level, will still need more water as they're more thirsty...especially as the roots die off and root mass/depth advantage is neutralized.

There are Tall Fescues that undergo complete dormancy (read up on Mediterranean types). But they are not used for TTTF breeding, likely because they go brown extremely readily in reaction to heat.

For further understanding on dormancy mechanisms, I personally would probably go into turfgrass biology textbooks (botany, essentially) to further my own understanding.

Finally, everything discussed here about Tall Fescue applies to Ryegrass as well. Ryegrass is no better at stress survival/dormancy....it's actually worse. Most here know that from experience, but for whatever reason, Fescue seems to get most of the hate thrown at it on this topic, time and time again.


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## moedank (Sep 10, 2019)

@Green, as usual, I appreciate your detailed responses. Thanks. :thumbup:


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