Most climates across the US have either extreme summer or winter temperatures that will cause a lawn to go dormant. When turf is dormant, grass blades “die” back, and grass growth stops allowing roots to conserve all the energy and rebound when weather conditions improve.
For warm-season grasses, even a mild winter can cause blades to brown and a dormant lawn to set in. Likewise, cool-season grasses will enter the dormant period when high-heat and arid conditions set in.
Since a dormant lawn is part of a healthy lawn’s life cycle, there are still some care techniques needed to prevent a dormant lawn from becoming a dead lawn.
Dormant grass, whether warm-season grasses or cold-season grasses, are more susceptible to damage, pest, weed, and disease issues, and lawn care practices should reflect that. Read on to learn if you should mow dormant grass and how to do it safely when you must.
Should You Mow Grass When It’s Dormant?
It is not advisable to mow grass when it is dormant as the weight of the lawn mower is enough to cause compaction, and too low of a mower height can scalp the blades and kill the grass. The blades of cold-season grasses, which typically grow taller than warm-season blades, are especially vulnerable to scalping during the summer heat.
Before grass enters the dormant season, you will want to have already cut it to the best height for the approaching season.
Blades of grass shade the soil, and grass clippings and thatch can act as a mulch layer locking in water to help prevent drought damage. Allowing taller grass in the spring can help shade the soil and reduce the damaging effects of hot sun and inadequate moisture in northern grasses facing summer.
After the heat has passed and irrigation is consistent deep watering, dethatching, and aeration can lead to deeper roots and faster recovery times.
For southern grasses facing winter, you will want to implement the opposite approach and cut the grass as low as is safe to do. Summer grass types can handle being cut to 2 inches if the one-third rule is applied over the fall season.
Letting summer grass grow tall at the beginning of fall and start cutting it back mid-fall will build a strong root network that can deal with frigid winters. Cutting the blades short before the dormancy stage of the colder months can prevent snow mold and accelerate the growth process at the end of the dormant periods.
Times to Avoid Mowing a Lawn
There are times throughout the year when our lawn faces stress that is above and beyond the normal run of things. For several weeks either in summer, winter, or both, lawns will enter a dormant season until soil temperatures are favorable again.
A grass-like fescue will need extra care in the winter, while St. Augustine grass will need protection from the cold. When grass is stressed due to any external factor, mowing should be avoided. Below are some examples of when a mow is a no-go.
|Time||Reason Not to Mow||Consequences|
|Winter Dormancy||The grass is brittle, and very little sunlight is available greatly reducing grass’ photosynthetic abilities||The grass may die at the root level and not come back in the spring resulting in bare spots or an entirely scalped lawn that needs to be replaced|
|Summer Dormancy||Cold-season grasses typically thrive on high levels of moisture, and plants like fescues go dormant to prevent excess liquid usage||Cutting leaves can cause damage to the blades, and grass loses precious water needed to survive and slowing the growth process after the dormancy stage especially if dull blades or the wrong mower blade is used|
|Extremely Wet||Soil that is wet can easily become compacted, locking roots into areas of low oxygen and causing health issues||Compaction leaves little air for roots to get oxygen from and makes grass blades highly susceptible to weed, pest, and fungal diseases, all of which can be fatal to turf|
|Extremely Dry||When grass is dry, the grass blade height can not be reduced quickly, or the grass crown will be cut, and you will have dead grass||When preparing grass for winter, healthy grass plants should be reduced slowly to the proper grass height, or leaf blades may die|
|Heavy Traffic||During dormancy periods, dry periods, the hottest periods, or the coldest heavy foot traffic can damage your lawn and lead t compacted soil and make the lawn uneven||Dry soil and the increased risk of soil compaction from heavy traffic during dry summer months can kill your lawn just as easily as the damage to roots foot traffic causes in the winter months|
|Weed Infested||The dormancy period for grass is often the active growth period for weeds, and mowing leaves or other lawn care operations can spread weed seeds throughout your lawn||Sick leaves and the spread of all kinds of pests occur when lawns have not been cared for before the period of dormancy, and mowing occurs when it should be avoided|
Will Mowing Help Break Dormancy?
Mowing during dormancy will not help your grass grow faster and, in most cases, will likely harm the blades and the roots and prevent a quick spring-up after the stressful period has ended. Mowing the lawn in the correct way both before and after dormancy ends, on the other hand, can greatly increase healthy grass growth when your turf breaks dormancy.
Giving your grass a deeper watering and after drought, more frequent watering can also speed up your grass’s green growth.
How to Mow Dormant Grass?
If you find that you have to mow dormant grass, there are several things you can do to make it less stressful and prevent irreversible damage. Watering deeply a day or two before, using the mower at the maximum effective height, and mowing in a different pattern every time are all ways to keep your turf safe from ill-timed lawn care.
Dormancy in the grass is often caused by a lack of moisture, and compaction on parched soil is much more common than on springy moist turf. Running a mower over thirsty soil is a sure way to kick up dirt, spread weed seeds and fungal spores, and compact the earth, making it harder to absorb the scarce water.
If you will be running a mower to collect leaves or to snip the tips of grass for a uniform look, then you should water deeply a day or two before mowing to give the blades time to flex and the soil a chance to hydrate.
Keeping the mower deck high is another way to ensure you do not kill dormant grass while mowing. Usually, it is recommended not to mow more than a third of the grass blade at once, but when dormant, try to keep that to half an inch.
This will take off the top of the grass but not damage the crown or promote as much liquid loss. Make sure to use sharp mower blades when cutting during dormancy.
Mowing the same path and direction will cause ruts and compaction during active plant growth and is even more dangerous when the grass is dormant. if you need to mow, wear spiked cleats to aerate as your go and reduce compaction.
Try to keep the mower with minimum fuel to lighten the load, and plan your cut to avoid going over the same areas too many times. This strategy can help reduce any damage done should you mow dormant grass.