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Closeup of the center and partial petals of a deep yellow sunflower.

High heat causes sun scald on your lawn!

High heat can lead to all kinds of issues in and on your lawn including browning, drought stress, and sun scald.  To break down the process of high heat and or a lack of rain on your lawn, think of how you would feel leaving in the middle of the winter and arriving in a hot climate like Mexico.
The first stage begins as sun scald if the turf has been growing fast and you get some hot, sunny days.  The turf turns white and you may see blotches or patches in your lawn appear virtually overnight.  Cool season grass is exactly that, it prefers cooler weather- not the high 80’s or 90’s- such weather places a huge demand for moisture on a shallow root system.
At first, there may be plenty of water in your soil, but after a few days to a week, that supply dries up and now the grass starts to suffer- it turns a dull- hazy purple with a blue tint.  This is the first symptom- drought stress- the grass is starting to dry up and is unable to meet the moisture demand of the leaf blade growing.  So now what happens?  The base of the plant is the command center, it is called the crown.  It cannot push out any new growth and now must shut down on emergency power to save itself.
The second stage is browning- the grass visually turns brown as the once green leaf blades dry up and the crown starts to shut down to conserve what is left and survive.  The good news is, the sooner you water- the sooner your grass will reactivate and start growing again.  Typically, if you get water to your lawn in the initial drought stress mode, you can prevent or minimize subsequent browning and get things rolling again- keeping the grass green without tints of brown or drought stress.
However, if you allow the lawn to shut down and brown out, it can take weeks to a month to regain the green color and previous growth.  Simply put, once she goes brown- better turn around and keep the water running.  Therefore, targeting drought stress is your best option to prevent dormancy and a brown lawn during summer.
The good news is most lawns just have what is known as “hot spots”- sections with thin topsoil, ledge, septic covers, or sandy conditions.  If you target these “hot spots” first, more often than not you can avoid watering your entire lawn in some situations.  Just look for the drought stress and water those areas instead of the whole lawn.
What else can be done to avoid and or minimize browning and or drought stress?  Mow high, 3” minimum and don’t cut the lawn at high noon- this is not a western movie- mow in the am or late pm.  Better yet, if the lawn does not need a cut, don’t mow it at all- skip a week or two.  Your heavy tractor or mower will cause more damage by crushing delicate, weakened grass versus leaving it alone.  Fertilizing, liming, and other proactive treatments can keep the lawn healthier going into hot/dry weather and help the grass recover faster.  Avoid high soluble, quick release liquid fertilizer as this can burn and or cause an undesirable- unsustainable flush of growth.  Aeration can help break up compacted soil and allow water to penetrate the surface and down into the root zone.
In another post, I will discuss when brown grass stays brown and dies.  This condition is not always just from a lack of water, but from insect damage.  Stay thirsty my friend. . .