Mow the Lawn Tall

Mowing a lawn tall is one of the simplest practices for maintaining a beautiful lawn.  Mowing a cool season grass (bluegrass, fine fescue, or tall fescue) lawn at a taller height is important for several reasons related to the health and resilience of the grass. Cool season grasses thrive when mowed taller, typically between 2.5 to 3.5 inches, depending on environmental conditions and use. Here’s why:

Promotes Deeper Root Growth

• Taller grass blades allow the plant to produce more energy through photosynthesis, which supports deeper and more extensive root systems.
• Deep roots improve drought tolerance and help the grass access water and nutrients more efficiently.
• Deep roots provide sugars for microbes in the soil.  The deeper the roots dig into the soil the deeper the microbial population will be able to survive.

Shades the Soil

• Longer grass blades shade the soil, reducing water evaporation and keeping the soil cooler.
• This shading effect suppresses weed germination, as many weed seeds, like crabgrass, need sunlight to sprout.

Improves Disease Resistance

• Taller grass is less stressed and more robust, making it better equipped to resist diseases such as necrotic ring spot.
• By maintaining sufficient blade length, the grass has more energy reserves to recover from stress or fungal infections.

Enhances Turf Density

• Cutting cool season grasses too short (scalping) weakens the grass, leaving it thin and patchy.  When a lawn is cut too short the roots must use energy to repair the damaged grass instead of growing a new blade of grass via rhizomes. 
• Taller mowing heights encourage a denser turf, reducing bare spots that could invite weeds or diseases.

Protects Against Heat Stress

• Cool season grasses are susceptible to summer stress. Taller grass provides a natural insulation layer, reducing the risk of damage from high temperatures.

Reduces the Need for Watering

• Deep digging roots and by shading the soil and reducing evaporation, taller grass helps retain soil moisture, decreasing the lawn’s watering needs.

Minimizes Clippings

• Frequent mowing at a taller height typically results in shorter clippings, which decompose quickly and return nutrients to the soil without creating a thatch layer.

Key Mowing Practices:

• Avoid Cutting More than One-Third of the Blade: Follow the “one-third rule” to minimize stress—never remove more than one-third of the grass blade at a time.
• Mow Regularly: Regular mowing ensures the grass remains at the optimal height without requiring a drastic cut.
• Sharp Blades: Use sharp mower blades to create clean cuts, reducing damage and disease risk.

Maintaining a taller height for your cool season grass lawn supports its natural growth habits, enhances its appearance, and reduces maintenance challenges over time.