Mowing Height for Cool-season Grasses
Bluegrass - 2 to 2 1/2 inches
Perennial Ryegrass - 2 to 3 inches
Fescue - 3 to 4 inches
Mowing Height for Warm-season Grasses
Bermuda - 1 1/2 to 2 inches
St. Augustine - 2 to 3 inches
Zoysia - 1 to 2 inches
These are basic guidelines for mowing heights. Keep weather conditions (hot, cold, drought) in mind whenever you mow.
Remember that mowing is pruning. Proper mowing increases the density of the lawn, which in turn decreases weeds. Each type of grass has a recommended mowing height. Find out which type of grass is in your lawn (you may have more than one) and mow at the proper height.
Stick to the 1/3 rule — never remove more than 1/3 of the grass blade length at any one time. A healthy lawn can survive an occasional close cut. Repeated close mowing produces a brown lawn and has several harmful side effects, including:
- Injury to the crown, where new growth generates and nutrients are stored.
- Reduction of the surface area of the blade, making the blade surface insufficient to produce food through photosynthesis.
- Increased vulnerability to pests and disease.
- An increase in the sunlight reaching weed seeds, allowing them to germinate.
- Risk of soil compaction.
Also remember to:
- Mow when the grass is dry. The blades will be upright and less likely to clump when cut.
- Avoid mowing in the heat of the day to prevent heat stress on your grass and yourself.
- Keep mower blades sharp and balanced. Ragged cuts made by dull blades increase the chance of disease and pests.
- Change the mowing pattern each time you mow. Grass develops a grain based on your cutting direction, tending to lean towards the direction you mow. Alternating the pattern causes more upright growth and helps avoid producing ruts in the lawn.
- Mow moving forward, whether you're pushing a walk-behind mower or sitting behind the wheel of a lawn tractor.
- Discharge the clippings (unless you bag them) towards the area you have already cut.
- Leave clippings on the lawn unless they form clumps or rows. This technique (known as grass cycling) returns nutrients and nitrogen to the lawn.
- Consider using a mulching mower or mulching attachments.
- If you bag your clippings, consider composting them.
- Mow grass higher in shaded areas under trees. In these areas grass has to compete with tree roots for water and nutrients.
- Reduce mowing frequency and raise the mowing height of cool-season grasses when hot, dry weather slows their growth rate.
Mowing new grass
Newly-seeded grass needs three to four weeks to get established after germination before you should mow it for the first time. The grass blades are tender and easily damaged and the foot and mower traffic could compact the soil, especially if the soil is moist. Mow when the new grass is 3/4 inch to 1 inch taller than its recommended regular mowing height.