What Is the Proper Height to Mow Perennial Ryegrass?

Mowing Height

• Strive to mow perennial ryegrass lawns at a height of 2 1/2 to 3 inches. This grass will grow much lusher and faster during fall and spring when the temperatures range between 35 and 80 degrees Fahrenheit. In the cooler seasons, perennial ryegrass may be mowed slightly lower, as short as 2 inches. Do not cut this lawn grass shorter than 3 inches during the hottest months or when drought conditions prevail.

When to Mow

• Timing the mowing maintenance is nearly as important as the correct mowing height on all lawns, regardless of turf grass species. To keep perennial ryegrass its healthiest, never remove more than one-third of the total grass height at any one mowing. For example, if the lawn is 3 inches tall, never cut it more than one-third its height -- or lower than 2 inches. Cutting off more than one-half the height of perennial ryegrass stresses the plants, stunts regrowth and can expose the lower sheaths to make the lawn look more tan or yellow-green.

Improper Mowing Height Consequences

• Cutting a perennial ryegrass lawn too short, especially during dry periods or when summer temperatures consistently get to 90 F or warmer, can induce dormancy. A longer or taller lawn encourages deeper root growth into the topsoil, and the leaf blades shade the soil and roots from the hot, drying sun rays. Short or scalped ryegrass lawns suffer from increased soil temperatures, warmer soil and shallower roots. Heat and dry soil cause perennial ryegrass to yellow or burn thatch brown in a temporary seasonal dormancy. Lawns mowed too short also expose bare soil for weeds to infest more easily.

Winter Care

• As a cool-season grass, perennial ryegrass continues to grow -- albeit at a progressively slower rate -- even into the early winter until cold temperatures or snow cover force dormancy. To prevent fungal diseases from starting over the winter, mow your perennial ryegrass lawn at 3 inches tall in middle to late fall until it finally stops growing. Don't let it become a billowy meadow with arching blades 4 or 5 inches long. The 3-inch height keeps ample biomass while still allowing good air and light penetration over winter, making the grass better prepared to green up and be healthy with spring's return.