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Mowing dormant grass, what is the best way?

A dormancy period occurs within grass when there is inadequate moisture available. This essentially means the grass ‘goes to sleep’ to conserve resources. Brownish-tan leaf blades indicate it. Typically, dormancy may occur during drought in summer conditions and colder months.

Mowing dormant grass, what is the best way?

Generally, it’s best to mow your lawn before the dormant period starts. This allows the grass to grow healthier after dormancy, preventing damage from fungi and bacterial growth. During dormancy, the grass is subject to great stress, and growth is minimal. Mowing during that period is not a good practice.

This article will discuss the dormant periods that occur in summer and winter. The aim is to inform you about the dormancy period of different types of grass and the ideal mowing heights for each grass type, and the problems that occur when the grass is mowed too short during these periods. So, regardless of the grass growing in your lawn, this article will highlight all the ways you can easily revive it from dormancy.

Dormancy during summer

Grass becomes dormant in summer in response to the stress caused by intense heat and drought, which can burn the grass. While grass can survive for three to four weeks without dying in a dormant state, if the drought or heat is intense enough, it may kill grass over time.

Dormancy during winter

Grass goes to a dormant state during the winter months, turning brown to conserve water and nutrients to sustain itself.

Mowing during summer and winter dormancy

It’s important to maintain a good grass height during summer to protect the roots from the harsh heat. Longer grass also helps to reduce water loss and prevent weed invasion.

Fall and winter months can make taller grass matted and diseased; therefore, mid-length grass is preferable during these seasons. It’s important to avoid overcutting the grass as growth is minimal during these seasons and can expose the roots to damagingly cold temperatures. Ultimately, to avoid serious harm, you should focus on maintaining a good grass length without overcutting it.

It’s always advisable to mow the lawn before the dormant period begins. This encourages the growth of roots after the dormant period ends and protects your lawn from getting damaged by fungi or bacterial growth.

However, if you haven’t mowed the lawn before the start of the dormant period and your grass is too tall, following the one-third rule, you can still mow your lawn to neaten its appearance. The one-third rule demonstrates that you should never cut more than one-third of the blades’ height because doing so can be harmful.

Effects of mowing the grass short during dormancy

A dormant lawn becomes more vulnerable to weather stress, weeds, and diseases if it is mowed too often. The growth of the roots is also inhibited, consequently mowing the grass too short leaves fewer blades available for photosynthesis, which damages the growth process and weakens the roots, making them less able to endure drought.

Short grass requires protection from pests, weeds, disease, and drastic weather conditions, such as during the summer, when the turf is exposed to direct sun, which causes it to dry quickly.

Dormancy and different types of grasses

Before discussing the ideal mowing heights during dormancy, let’s look at when different types of grass go dormant. Each grass type has specific characteristics for surviving through different seasons; therefore, it’s crucial to identify the grass type in your lawn to ensure you can adequately revive it from dormancy.

Suppose you live in the Pacific Northwest, Midwest, or Northeast regions of the U.S. In that case, your grass falls into the category of cold-season grasses, which include Tall Fescue, Fine Fescue, Kentucky Bluegrass, or Perennial Ryegrass. As the name suggests, cold-season grasses are suited to cooler climates and continue to grow throughout the cold seasons.

Cold-season grasses, however, require extra care, including frequent watering, to survive the hot seasons. These grasses also tend to go dormant in both summer and winter. For example, Kentucky Bluegrass and Fescue go dormant for a short period during both seasons, and they require final mowing in May and December.

If you live in the Southern or Southwestern areas of the U.S, your grass belongs to the category of warm-season grasses, which include Bahia, Bermuda grass, Centipede, Zoysia, and St. Augustine.

Warm-season grasses go dormant during winter and experience very little or almost no growth at all during these months. During this period, these grasses require less maintenance, watering, and zero mowing. For example, Bermuda grass and Buffalo grass grow during summer and enter dormancy in late fall, so they require final mowing in October.

Mowing heights and dormant grass

Proper mowing height promotes deep root growth and increases the density of the grass, which helps the turf fight against environmental stresses, such as weeds and diseases.

When the dormant season is approaching, you should give your lawn a final mow and allow it to grow to the recommended height. Always bag the clippings and rake extra leaves from the lawn before it enters the dormant state. Taller grass has deeper roots and a more extensive root system that allows it to withstand weather stress during dormancy.

Once dormancy starts, try to avoid mowing your lawn, as its growth has nearly stopped, and it’s already under a lot of weather stress. Mowing can damage the roots, which is the grass’s only hope for revival post dormancy.

Mowing the lawn at the proper height is vital for its health. The ideal height for mowing varies based on grass type, weather, and growing conditions. It is important to determine the ideal height and allow it to grow one-third higher. You can set the mower height by adjusting it on a flat surface and measuring the ground’s distance to the blade.

The following chart shows suitable mowing heights for different grass types and at what height you should mow it.

Grass Type
Recommended Mowing Height (inches)
Mow When Grass Reaches This height (inches)
11/2 – 2
Bermuda grass
1-1 1/2
11/2 – 2
St. Augustine
2 1/2-3
3 3/4-4 1/2
1 1/2-2
Kentucky Bluegrass
2-2 1/2
3-3 3/4
Tall Fescue
3-4 3/4
Fine Fescue
2-2 1/2
3-3 3/4
Buffalo grass
1 ½-3
Colonial Bentgrass
½ -1
¾ – 1 ½
½ – ¾
¾ – 1 ¼
Kikuyu grass
1-1 ½
1 ½  – 2 ¼
Perennial Ryegrass
1 ½ – 2 ½
2 ¼ – 3 ¾

Warm-season grasses, such as Zoysia, Bermuda grass, St. Augustine grow the most during summer. Mowing heights can vary within the sub-categories of the same grass. For example, Zenith Zoysia grows better when it is cut to 1.5 inches, while the ideal height for Empire Zoysia is 0.75 to 3 inches.

Cool-season grasses such as Kentucky Bluegrass and Fescues grow better in spring and fall and, in general, must be cut from between 1 to 4 inches.

If you follow the recommended heights for your grass shown in the above table, your lawn will have a high chance of surviving dormancy and thrive again when the growing season starts.

Mowing after dormancy

After dormancy, your lawn will begin to revive, encouraging green growth. Having survived weather stress, grassroots will begin to grow and gather essential nutrients, so frequent watering is essential for grass to grow healthy in the growing season.

When the grass is completely recovered from dormancy and looks healthy and green, you can now mow the lawn to a suitable height.

The 1/3rd rule

As a rule of thumb, never remove more than one-third of the grass blade in a single mow, as this reduces the carbohydrates necessary for healthy growth. In other words, allow the grass to grow one-third higher than your ideal height before mowing it. Mowing more than one-third of the leaf tissue during dormancy may cause scalping, and the grass will not be able to recover from its dormant condition.

Mower’s blades and dormant grass

It’s also important to check your mower blades before mowing your dormant lawn. It’s often said that dull blades are the worst thing you can subject your lawn to. Dull blades could result in rough and ripped grass that looks uneven.

When the dormant grass is cut with dull blades, its sick leaves are vulnerable to diseases, and as its growth is already inhibited, the leaves are unable to regenerate faster. To avoid ruining your lawn, inspect your mowing blades, and if there are chips and gaps in between them, it’s probably time for a new one.

Basic tips for mowing dormant grass

  • Suitable height: Mow the grass to a suitable height beforehand to prepare it for the dormant period.
  • Avoid mowing when dormant: Avoid mowing the grass unnecessarily during the dormant period.
  • Lower height after: After dormancy, cut the grass to a lower cutting range to remove dead, dormant blades.
  • Drought: During drought summer conditions, reduce the stress on your lawn by allowing the grass to grow to the upper cutting range.
  • Snow mold: To prevent snow mold, mow the cold-season grasses shorter for the final fall mowing.
  • Change pattern: Change your lawn mowing pattern every time you mow your lawn.
  • Sharp blades: Use sharp blades while mowing the dormant lawn.
  • Mow when dry: Always mow the lawn when the grass is dry.

Final word

Dormancy is a natural process that can’t be avoided. The best practice is to prepare your lawn for the dormant period to have the strongest chance of survival. During dormancy, grass growth is minimal, so mowing during this time is damaging. Instead, preparing beforehand is essential. The trick is to mow the lawn before the start of the dormant period to a suitable height and avoid mowing once the dormancy strikes. This will help the grass survive the stressful period and allow the leaves to grow after the dormant period is over. However, if you must mow your lawn during dormancy because it looks rough, always keep the one-third rule in mind.