Stemminess in cool-season turfgrasses (bluegrasses, ryegrasses, bentgrasses, and fescues) appears to be more of a concern this year than in some previous years.
Flower bud initiation in cool-season turfgrasses occurs during fall's shortening days and cooler temperatures; the following spring, under appropriate conditions, these grasses become reproductive and begin flowering. Mowing, of course, leaves only the remnants of the flowering stem (culm) and its associated blades. After flowering, the reproductive shoots (stems and attached leaves) die and begin to decompose. In turf, the dying shoots intermingled in the nonflowering grasses produce an uneven, mottled appearance. Often, appearance is made worse when the tough stems are shredded or ripped rather than cleanly cut. In fact, in turf mowed with reel mowers, flowering stems may lodge and not be cut at all.
What to do? First, understanding the natural growing cycles of these grasses won't reduce stemminess, but it is helpful to know that as the growing season progresses, the flowering stems decompose and become less of a problem. Second, nitrogen fertilization can reduce flowering. Evaluate your fertilization program. If you're supplying only one or two pounds of nitrogen per 1,000 square feet per year in sunny areas, increasing to three or four pounds may improve overall turf quality. Nitrogen fertilization, however, can be a double-edged sword. Be careful not to apply excessive nitrogen, because root growth may be impacted and the severity of some diseases enhanced. Finally, be sure to mow frequently and maintain sharp mower blades. Frequent mowing will keep culms from being pushed over rather than cut, and a sharp blade may reduce ragged, ripped ends on stems, which detracts from turf appearance.