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Identifying and Dealing With Heat Stress In The Lawn

by Allyn Hane 10 May 2018

See that picture down there? You are either, “Primed!”, “avoiding the hangover” or “doing the happy dance” this coming weekend. It’s a tale of cool and warm season grasses and the development and exit of Spring... and you’re invited to take the ride. But hurry… this weekend is when things REALLY heat up, literally.

I swiped this image from Twitter and added my own definitions in yellow to serve as a visual for you:


Minneapolis... Bozeman… even Bismark... YES! Frickin BISMARK! You are coming into the prime time! Temps are right in the perfect window for your cool season grass types, especially Kentucky BlueGrass. It should be double dark and reaching for the sky. Make sure you mow in some stripes and hit me on Twitter with them.

If you are a beginner, your first choice right now is to go get my dandelion guide and get your guns ready because the yellow scourge is going to nail you hard… without notice!

Next, you should plan to get some pre-emergent down - you’re in a good window for dithiopyr. If you have my Cool Season Hybrid Organic Lawn Plan, you start right in at Spring Step #2. Seriously, you are 100% primed to start right there.

No Spring Hangover

So you guys in through the meat of the midwest there - I’m looking right at you Indianapolis, you too, St Louis… even you Philly! - you are in for it this weekend and following days and I want you to be prepared! The heat is going to come in fast and your turf is not prepared, I promise you.

It’s been fat and happy all spring getting plenty of good rain, mild, sunny days; low humidity. These have been long awaited, happy days for both you and your lawn. You’ve drank it in and imbibed on Nitrogen. You are buzzing with pride, drunk on the double dark. No care in the world. Flowers are blooming, Robins are patrolling, rabbits are breeding.

But the weekend is coming. (any G.O.T. fans?)

Let me explain the prophetic diagnosis above here for our friends in St Louis. Sometime right about the time you are reading this - your lawn is going to be in perfect condition. It will be the greenest it’s been all year - especially coming off those thunderstorms predicted there today (Wednesday). Unbeknownst to you and your High Nitrogen drunken lawn… that 87-89 degree heat has zapped your fluid and nutrient levels and a shutdown response has been triggered.

Rising humidity, strong winds, and zero rain those days are going to wreak havoc and areas of the lawn are going to start to turn this dark steel-blue-gray -- and when the sun does peak out in the hottest part of the afternoon, some of that steel gray will begin to exhibit shades of brown. Panic will set in! What is this trickery?

It’s heat stress, and your lawn was not expecting it, here is what it looks like:
Identify Heat Stress In The Lawn

What Should You Do?
Right now, nothing really. Just continue to mow tall, limit foot traffic, and monitor. It’s actually good for the lawn to get this little pre-summer jolt. It needs to start slowing down anyway and wean itself off the “everyday-thunderstorm” bottle.

You’ll notice that in my Cool Season Hybrid Organic Lawn Plan, I start to back you down on your Milo rates as well. We want to keep her green, but we don’t want to push more growth when these kind of temperature spikes are going to become more common or even the norm.

Now, if things persist, that’s when you have to be ready to spring into action. These are the wild cards over the next 3-5 weeks:

  1. Are temps going to persist over 85 and push 90 for sustained days with...
  2. More and more direct sun and fewer clouds, higher humidity
  3. Wind to dry out the tips, shafts, and crowns.

This is the perfect scenario for the lawn to get heat stressed and even check out and off into summer dormancy. And as you will see in this video, it’s not easy to bring a lawn back once it gets away from you.

Action Items:

First off, let this be your wakeup call that it’s time to get your irrigation strategy ready to launch at any moment. I recommend Impact Sprinklers. The one that I have had for many years that has served me best (and that appears in these videos I am linking) is this Melnor Impact Sprinkler:

Here you can see where Amazon reminds me that I already bought this one many years ago - and I still have it today… somewhere. (They are not a sponsor. I bought this and have always like it)

The only drawback is the base is light and won’t stay in place so you need a brick to hold it down - however, I like that because it allows me to bend the stream to cover odd-shaped areas of the lawn. (ever wonder why most lawns are square but sprinklers cover a circle?)

Another impact sprinkler that I did get not long ago was this one from Gilmour:

It’s plastic but well made… and has the ability to really adjust the stream in a way that is quite unique. Just bringing that “track” up or down can really help you bend the stream across your lawn and cover some very odd shapes easily - all while retaining the advantages of an impact sprinkler. I do highly recommend this one as well. However, same deal, you will need a brick to hold it in place. You can see a clip of a pie-shaped area I used it on last year.

Here is exactly how to water your lawn all summer:

It’s ok to let the turf feel and show stress a bit... ...but if it starts to go brown like in the picture above, get water on it immediately - water deeply and infrequently letting the soil dry out between irrigation cycles. If you get rain help, adjust.

Last thing here:
If you want to help your lawn sustain itself more naturally during summer heat by building deep, dense roots, consider applying 3 oz/gallon of RGS every 3-4 weeks to the lawn, all year long. If you only incorporate that one item into your regimen, you will see a difference, especially at the extremes. I know I have not talked about disease issues, and trust me, I will. But using RGS as a part of your regular regiment should help reduce visible damage from disease anyway.

If not, I’m leaning towards Eagle this year for primary fungicide as it’s price has come down and it targets a wide variety of disease issues (Also great for apple scab in crabapple trees if you hit them right as the flowers fall off). Propiconazole seems to be losing its effectiveness over time.

Happy Dance!

My friends in parts south who have grass types like St Augustinegrass, Bermuda, Centipede, and Zoysia - you are now coming into prime time yourself! Our grass types thrive with temps nearing and even exceeding 90 degrees. Alpharetta, GA, I’m looking right at you folks.

Your Bermuda should be spreading like crazy. Now is the time to Thrower Down and push it. Hit it with Milo very 5 weeks, low dose and let it run. Same with you Zoysia folks - you are finally going to wake up yourself! About time right?

You guys also need to pay attention to irrigation as summer patterns are starting. Coastal folks like me down here in Florida will get plenty of rain and in my case, I won’t need to irrigate much at all after late May.

But you guys with warm-season turf in the interior should def get prepared. Your watering schedule is really about the same as the cool season guys. Get down ½” of water every 3-4 days.

If you are looking to get started with a program now, you can do that for sure… start right with my Warm Season Guide and get into the Memorial Day, May 28 step and start right there. That gives you plenty of time to prepare. Get used to mowing properly now, and irrigating… and then start the plan on Memorial Day with all the rest of us Lawn Care Nuts!

Your biggest key is mowing - mow mow mow and it will grow grow grow! Check out this video for beginners if you haven’t already.

Florida BlackOut Friends

Well, the party is going to end quickly for us, isn’t it? For those who are unfamiliar, most of Florida has adopted this fertilizer ordinance which states that no nitrogen or phosphorus fert can be added to residential (or commercial) properties from June 1 until October 1. This is due to the super-heavy downpours we get just about every afternoon. These downpours are so violent they will literally wash fert off sandy-soil lawns and into the storm drains which almost always empty out into waterways. (we are the land of lakes surrounded by golf and ocean). There are literal “dead zones” that are getting worse and worse so I fully support this ordinance.

So what’s the Florida LCN to do? First off, Throw’er Down now yo! Early, and often. Ha ha!

Your May 28 app is going to be a very special one of course… because it’s your last for a while. (mine too!)

If you want to sustain the green, I recommend you pick up some MicroGreen now and plan to spoon feed this in every 3-4 weeks all during the blackout. 3-6 oz/gallon will do it. I’m running with this program this year myself - so feel free to follow along!

First experiments are going to be released in a video this weekend.

Note: this Florida “no N or P” summer program using MicroGreen: this can be applied to cool season lawns as well - as long as you keep them irrigated. If you are interested in keeping your lawn green without pushing too much growth in summer, you should also consider spoon-feeding MicroGreen the very same way. It’s easy and you won’t mess it up. Get out and spray and pray.

With that, let’s hope for the best, and I’ll see you in the lawn!

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