Identifying and Dealing With Heat Stress in a Fesuce Lawn

Identifying and Dealing With Heat Stress in a Fesuce Lawn

Lawn Heat Stress:


Lawn heat stress can be a burden to homeowners when it sets in between May and September. Whenever a period of dry and hot weather rolls through, fescue lawns can go through periods of stress that end up impacting the appearance and health of the turf depending on how well it’s handled. In addition to lawn heat stress, other summer turf issues that can cause brown areas in a lawn include fungal disease and even dying weeds. The important thing for both homeowners and professionals is being able to tell the difference between these problems and knowing the different ways of handling them.

Lawn Heat Stress
A heat stressed lawn will show complete areas of brown; this lawn likely suffers from uneven irrigation coverage based on the healthy green next to the dormant brown.

Heat Stress


Turf type tall fescue, the lawn of choice in transition zones like Richmond, Virginia and the surrounding area, is a cool season grass. Cool season grasses differ from warm season grasses in that they handle mild and cool weather well, keeping them green through the winter. However, this also means that they struggle the most during the summer when temperatures get into the 80s and higher.

Lawn heat stress is when turf grass undergoes significant physiological stress and weakening caused by insufficient exposure to water paired with high air and soil temperatures. As a result, parts of a lawn may be more at risk of lawn heat stress than others, which is why many homeowners struggle with how to keep lawn green in summer heat. The tops of hills, strips of lawn beside roads and driveways, parts of the yard with little to no shade, and areas where irrigation does not reach are all at greater risk of lawn heat stress.

Because heat stress causes a weakening of the plant, some grasses like fescue will shut down and go into a form of dormancy in response to these hazardous conditions. When fescue goes into dormancy due to heat at drought, the rate of growth in the grass slows significantly. By barely growing, the grass doesn’t have to use nearly as many resources, and it can focus instead on strengthening its cell walls and other internal processes.

Heat stress in a fescue lawn can be viewed in three different stages. Stage one will still appear green in lawn areas, but turf will begin to feel dry even at the ground level and will need less and less frequent mowing. Stage two sees a purple tint begin to develop across the turf, making the grass almost look bruised; at this point, the grass will be barely growing if at all and will feel significantly dry to the touch. Stage three is the point at which a lawn is in serious trouble. The turf turns a light brown color and shrivels as the grass loses cellular moisture, feeling crunchy and almost like straw to the touch. The farther through the stages the lawn heat stress develops, the harder it will be for the turf to recover.

Unfortunately, because there is no way for a homeowner to control the weather, there are only two real ways to prevent lawn heat stress. First, a proper watering regimen is key. Second, a strong, carbon based fertilizer program properly balanced throughout the year to optimize root development and plant health makes a huge difference in color retention and longevity.

Lawn Heat Stress
Obstacles just below the lawn’s surface prevent roots from developing more than few inches, proving why it’s so important to have a deep root system once it gets hot outside.

Or Is It Fungus?


While lawn heat stress is a common cause of grass dying in summer, it can be commonly mistaken with brown patch, a fungal disease seen in fescue lawns during warm, humid weather. While heat stress is contributed to by a lack of water, brown patch is more common when too much moisture is being held within the turf and preventing the blades of grass from getting air circulation and drying off adequately. Both problems can exist within the same lawn, so it’s important to know the difference.


While heat stress is seen in different stages and is a uniform brown throughout the affected area of the lawn, brown patch will be random, irregular patches of brown turf within an otherwise green area. On the blades of grass themselves, a warm dampness can be felt close to the thatch layer, and individual blades of grass will be limp with distinct spots of brown appearing as blemishes on the plant tissue.

By getting up close at ground level, you can distinguish between lawn heat stress and brown patch. To correct brown patch, watering should be performed in the morning and only when necessary. Additionally, a fungicide regimen is most effective in not only halting the spread of the fungal issue, but in reversing it as well.

Lawn Stress
Brown areas in a lawn caused by fungus can be more subtle than heat stress at a distance, which is why it’s important to examine the turf up close.

Whether a lawn is suffering from heat stress, brown patch, or both, every homeowner wants to know how to keep grass green in hot weather. Through proper watering, proper fertilizing, and proper maintenance, even a fescue lawn can stay green and healthy during the summer months. If you see anything that makes you worried about your lawn, don’t hesitate to contact your local turf management specialist.

Heat Stress in a Fescue Lawn
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