Cool-season grasses, such as Kentucky bluegrass, perform best in the spring and fall months in Iowa. Hot, dry weather is tough on cool-season grasses. Kentucky bluegrass, for example, responds to hot, dry conditions by going dormant. High temperature stress of cool-season grasses can be reduced by simply raising the mowing height. The additional leaf area shades and cools the crowns of the plants. The higher mowing height also promotes the development of a deeper root system. Deep-rooted plants are better able to withstand drought stress. Finally, the additional leaf area increases the rate of photosynthesis or food production.
Mow Kentucky bluegrass lawns at a height of 2 to 2 1/2 inches during the spring and fall months. The recommended mowing height during the summer months is 3 inches.
An important key to proper mowing is a sharp blade. This is especially true during the summer. Dull blades tear and bruise the leaf tips. The hot summer sun bleaches the damaged leaf tissue, giving the turf surface a whitish appearance. The damaged leaf tissue also increases water loss and the potential for disease infection.
This article originally appeared in the June 8, 1994 issue, p. 84.