For cool season lawns that are primarily made up of grasses like Kentucky Bluegrass, Tall Fescue, or Perennial Rye the heat of summer can be tough to overcome. In some areas of the country drought is a problem. In other areas humidity and evening rain storms can be an issue. Still other locations the heat is the primary driver of summer dormancy.
No matter where you live or what combinations of summer stressors you are dealing with, these simple tips should help you get through the summer with as little damage to your turf grass as possible.
To serve you as best as I can I made a video summarizing a lot of my thoughts on summer lawn care. You can skip past this and read if you like but I encourage you to give this a watch too. It should help you visualize the steps needed to keep a green lawn through the summer heat.
Make sure to see the following articles for more on watering and mowing during heat waves:
First Of All
In the summer cold season grasses protect themselves by going into summer dormancy. This is when the grass goes tan or brown and looks like it’s dying off. This only occurs when the heat gets too high and not enough water via rain or irrigation gets into the soil to offset the heat stress.
If you don’t think you’ll get enough rain or irrigation on the ground to prevent dormancy then don’t fight it. Let the grass go dormant and resist the urge to fertilize, cut, or water often until the threats of summer start fading by late August.
A dormant lawn may look like it has died but it is actually protecting its root system and waiting for conditions to improve before greening up again and growing as fall takes hold.
A dormant lawn should be watered occasionally (once every few weeks) to keep moisture in the root system and foot traffic on the turf canopy should be minimized to limit damage to crowns and stems which will be a bit crispy.
If however you think you can keep your grass out of summer dormancy then you should formulate a plan to manage moisture on the grass as best as possible to keep the grass green and disease free.
Irrigation will be complicated by the timing and frequency of your summer rains as well as their intensity.
If you live in a humid environment then disease (fungus) will be a bigger concern. Rains that happen in the late afternoon and evening can easily cause a fungal disease in any lawn. If your late afternoon or evening rains are light then this is when you want to supplement with irrigation at the exact same time as the rain to ensure you get a full inch of water into the turf grass at once.
If the grass blades are going to get wet as the day is ending then you might as well get your full watering cycle in at this time so you don’t have to do it a few days later when the skies are clear. We don’t want to have to get our grass blades wet any more often than we need to.
If however you live in a dry climate or you are getting morning rain then stick to a rigid irrigation schedule that waters the lawn very deeply at dawn. The goal is to water enough in the wee hours of the morning to get a full inch of water down before everyone starts heading off to work.
If your irrigation system has multiple zones and you can’t get through all zones before it starts getting hot then choose different days to water different zones and start them running at 5-5:30am right when the sun is coming up.
Try to water each zone for a very long time so that you don’t have to run them as often. It’s better to water deeply once every 5-6 days then it is to water half as long every 2-3 days.
If you are open to the idea, purchasing a product like Hydretain in either spray or granular form, you can apply this once to your lawn at the beginning of summer and it will work in the lawn for up to three months retaining moisture in the soil. This kind of product allows you to spread your irrigation out even further, adding an extra day or two between watering sessions.
Over the course of the summer one single application of Hydretain can cut down on your watering sessions by about 1-2 sessions per month, probably five whole irrigations sessions over a 3-month period. The savings on water bills can offset much of the cost of Hydretain and the smaller amount of water hitting the lawn will also help prevent fungal diseases from taking hold too.
For more aggressive water retention strategies you can plan on core seating the lawn at the end of summer and top-dressing the lawn with biochar. The biochar will work its way into the topsoil and will hold water and nutrients better than just about anything else giving you an improved summer lawn in subsequent years.
Make sure to see this post for my thoughts on the best biochars for the lawn.
Assuming your lawn isn’t dormant and is green and growing you should take the extra time once a month or so to sharpen your lawn mower blade. Usually a mower blade will come off with a simple socket wrench and if you take a standard angle grinder to it you can usually put a pretty sharp edge on the blade in about 5-10 minutes time.
The sharp blade will help your grass retain moisture because the blades will be cut clean rather than shredded by a dull edge. A shredded leaf tip will have more surface area for moisture to escape.
A cleaner cut leaf blade will also be much more able to resist disease making this a practice that shouldn’t be understated.
Most grasses in summer will do better if you cut slightly less frequently and at a taller height of cut. Don’t go overboard with frequency, you still should be cutting regularly but if you were cutting every 5th day you should now be cutting every 6th or 7th day when the grass is an extra half inch high or so.
Tall fescue is even more tolerant to tall heights of cut as it can usually be maintained on the highest setting your mower will go through the summer.
For humid climates you will not want to push extra growth because that will force you to have to water and cut more often… this will make fungal disease a bigger problem and a more likely scenario as well. Fertilization should be minimized or eliminated unless you have reliable water delivery in the early morning.
Fertilization anywhere in any climate should focus on grass health or immunity first meaning low Nitrogen and high Potassium. You can get Potassium only fertilizers or stress blend fertilizers that typically contain equal amounts of N & K.
Organic sources of nutrients are always better in the summer as well because their effects are usually spread out over a longer period of time resulting in slower growth and a lower chance of over fertilizing.
For more in depth information on summer fertilization see the following post: Should You Fertilize Your Lawn In The Summer?
Lastly, summer weed pressure can start getting intense in the summer, especially for people that don’t apply a weed pre-emergent in the Spring or for those that put that pre-emergent down too late.
Summer weeds will usually thrive in heat so make sure to cut your lawn with a bagger higher than the grass height from time to time to chop the seed heads off of the weeds before they drop them.
You can also spray weeds in the summer but only if temps are lower than 85-90 degrees. Stressed lawns will be negatively affected by weed killer products above this temperature range although strong lawns that are largely stress free can usually deal with weed killers well into the 90s regardless of what the bottle says.
Best practice however is to simply remove seed heads by hand plucking or with a bagger mower on a high setting so as to limit the weeds growth and minimize the seeds that will turn into weeds in the following years.
Near Summer’s End
As summer starts drawing to a close in late August this is the perfect time to overseed your lawn. Assuming temps have softened a bit you can usually get away with putting grass seed down on thin areas of the lawn or better yet you can get away with running a dethatcher (scarifier) over the lawn and then overseeding.
At the end of summer a well watered lawn will germinate new grass in those thin areas very quickly and the new grass will be easily able to mature enough to overwinter.
Assuming you take all the early tips in this guide into consideration though, overseeding may not be needed by the end of summer and you’ll have a very healthy lawn going into fall.
There’s So Much More To Lawn Care
If you you have read this much about keeping a lawn through the summer then you probably care about your lawn a lot.
Take a look at my other lawn care guides to make sure your other projects out in the lawn are successful!