Should the First Mow of Spring Be High or Low?

The General Rule

• Regardless of whether your lawn is composed of cool-season or warm-season turf grass, the universal lawn mowing rule is to never remove more than one-third the total height of the lawn at any one mowing. The growth of the lawn and the time at which you get around to making the first mowing of the spring season determine what height you should mow. For example, if the lawn is 5 inches tall before you finally mow, no more than 1/3 should be cut off to preserve the health and vitality of the turf. Therefore, mow the 5-inch-tall lawn no lower than 3 1/4 inches. If your first springtime mowing occurs when the grass is only 3 inches tall, set the cutting blades to be no shorter than 2 inches.

Insight

• After the winter, the lawn may not have left dormancy at the same rate or experienced the same growing conditions in the soil. Sunny, warmer parts of the lawn may have started growing a month before areas with shadier conditions, with cooler and moister ground. Therefore, to bring the entire lawn up to a similar height and vitality, mow the lawn on the high side during the first spring mowing. This ensures the tallest grass is cut back by no more than one-third its height, but shorter grass is allowed to grow to make food in more leaf surface area. A month later, the overall height of the growing grass should be more consistent across all parts of the yard.

Considerations

• If you like to maintain your lawn grass on the short side, you need to invest the time to conduct more frequent mowing. Remember, never cut off more than one-third the lawn's height at each mowing. If the springtime, when weather isn't conducive for good growth -- cool and moist for cool-season grasses or warm and moist for warm-season grasses -- you shouldn't mow too frequently. If the soil is dry, longer grass and a higher mower cutting height promote deeper root systems and an increased resilience to drought. Cutting a drought-stressed lawn too short increases the stress on the lawn grasses, potentially leading to yellow or brown patches. Scalped soil areas become ideal locations for weeds to sprout and infiltrate the lawn.

Seasonal Changes

• If the lawn grasses are growing well and environmental conditions are ideal, you may mow a cool-season or warm-season lawn to a shorter level. Cool-season grasses, such as ryegrass, bluegrass and fescue, may be mowed shorter in spring compared to the more stress-inducing heat and drought of summer. Conversely, warm-season grasses, such as Bermuda grass, zoysia and St. Augustine grass, may be mowed shorter once springtime temperatures are warm to hot, which increases these plants' growth rates.

Recommendation

• If unsure about the appropriate lawn mowing height, contact a horticultural agent or turf grass specialist at your county's cooperative extension office. He will answer questions about your lawn, especially about benefits and consequences of mowing heights in springtime based on your region's climate and soils.