Can Grass Grow Too Long? Why Excessively Long Grass Can Damage Your Lawn
When it comes to mowing your lawn, we often hear that mowing higher is better. And that’s true! Taller grass generally develops deeper roots, shades the soil, and helps your lawn withstand summer heat and drought. But can grass grow too long?
Yes. While mowing higher is beneficial, allowing your grass to grow excessively long can actually hurt your lawn. It can increase disease pressure, reduce grass density, encourage weeds, and make mowing more stressful for the grass.
For homeowners in Minnesota and Wisconsin, finding the right balance between mowing height and mowing frequency is an important part of maintaining a healthy lawn.
What Is Considered Too Long for Grass?
At bioLawn, we generally consider grass taller than 6 inches to be excessively long for a maintained home lawn. We recommend mowing between 3 and 4.5 inches, with 4.5 inches being our highest recommended mowing height during the summer.
This allows the grass to maintain plenty of leaf surface for photosynthesis, while keeping the lawn at a manageable height.
Most lawns should be mowed approximately once per week during the growing season. However, during periods of rapid growth, especially in the spring and fall, more frequent mowing may be necessary.
The goal is to mow regularly enough that your grass never becomes excessively long.
5 Problems Caused by Excessively Long Grass
1. Cutting Long Grass Causes More Stress
Mowing is a stressful event for grass. Every time you mow, you remove a portion of the leaves the plant uses to produce energy through photosynthesis.
When grass becomes excessively long, bringing it back to the recommended height may require removing a large amount of leaf tissue at once. This reduces the plant’s ability to produce energy and can make it more vulnerable to heat, drought, insects, and disease.
Cutting excessively long grass too short in a single mowing can also expose older, less green portions of the plant, leaving your lawn looking yellow or brown.
2. Long Grass Can Trap Moisture and Encourage Disease
As grass gets longer, the blades can bend over and lay against one another. This creates a dense canopy that restricts airflow and allows moisture to remain on the leaves for longer periods.
Many common lawn diseases develop more readily when grass stays wet for extended periods. In Minnesota and Wisconsin, diseases such as dollar spot and leaf spot can become more problematic when environmental conditions favor infection.
Regular mowing helps maintain an upright, open canopy that allows grass blades to dry more efficiently.
3. Infrequent Mowing Can Lead to Thinner Grass and More Weeds
Grass responds to regular mowing by maintaining growth near the base of the plant. When grass is allowed to grow excessively tall for extended periods, it can become less dense near the soil surface.
A thinner lawn leaves more opportunities for weeds to establish themselves.
At bioLawn, we frequently remind homeowners that a thick, healthy lawn is one of the best defenses against weeds.
4. Excess Grass Clippings Can Smother Your Lawn
We generally recommend leaving grass clippings on your lawn. As they break down, they return valuable nutrients and organic matter to the soil. However, when grass becomes excessively long, mowing can produce more clippings than the mower can effectively distribute.
Instead of filtering between the grass blades, the clippings form thick clumps on the lawn. These clumps can block sunlight, trap moisture, and smother the healthy grass underneath. If left in place, they can cause yellowing and even grass death.
5. Excessively Long Grass Can Shade Its Own Growth
Grass needs sunlight to produce energy through photosynthesis. When grass grows excessively tall, the upper leaves can shade the lower leaves and growing portions of the plant.
Over time, this reduced sunlight can contribute to weaker growth near the base of the lawn and lower grass density.
This is one reason lawns that have been allowed to grow excessively long sometimes appear yellow or thin immediately after mowing. The greener upper growth has been removed, exposing the shaded grass underneath.
Regular mowing helps maintain a more uniform canopy and encourages healthy growth throughout the lawn.
What Can You Do If Your Grass Has Grown Too Long?
The good news is that excessively long grass doesn’t necessarily mean your lawn is permanently damaged. In most cases, you can improve its condition by adjusting your mowing practices.
- Start mowing more regularly. Establish a consistent mowing schedule, generally around once per week. During periods of rapid growth, you may need to mow more frequently.
- Lower your mowing height gradually. If your grass is 7 or 8 inches tall, don’t immediately cut it down to 3 inches. Instead, lower the height over multiple mowings to reduce stress on the grass. Allow some recovery between mowings.
- Manage excessive clippings. If mowing produces thick clumps of grass, spread them out, mow again to break them into smaller pieces, or collect them. Avoid leaving large piles of clippings on the lawn.
- Mow when the grass is dry. Wet grass is more likely to lay over, clump together, and produce an uneven cut. Whenever possible, mow after the grass has dried.
- Maintain an appropriate mowing height. Once you’ve returned your lawn to a manageable height, maintain it between 3 and 4.5 inches. During summer heat, we generally recommend mowing toward the higher end of that range.
Remember, the goal isn’t to mow your lawn short. It’s to mow your lawn consistently.
What Can bioLawn Do to Help?
If your lawn has become thin or damaged from excessively long grass, bioLawn can help restore its health.
Identify stressed or damaged areas. Our lawn care specialists can evaluate your lawn to determine whether excessively long grass, disease, or other growing conditions are contributing to the problem.
Overseed with improved grass varieties. If areas of your lawn have become thin, we can introduce newer varieties of grass that are selected for improved performance in Minnesota and Wisconsin lawns. These improved varieties can help increase lawn density and improve its ability to compete with weeds.
While we can help repair damaged areas and improve lawn density, proper mowing remains one of the most important things homeowners can do to maintain a healthy lawn.
The Bottom Line: Mow Higher, But Mow Regularly
At bioLawn, we encourage homeowners to mow their lawns higher because it promotes stronger roots, improves drought tolerance, and helps keep weeds out.
But there is a limit to how long grass should grow. We recommend maintaining your lawn between 3 and 4.5 inches and avoiding grass heights above 6 inches.
Consistent mowing encourages a thick, healthy lawn, reduces unnecessary plant stress, and helps prevent many common lawn problems.
If your lawn has become thin or damaged, bioLawn can help identify the cause and recommend a plan to restore healthy grass.