Problem: Seedheads in Lawn
Lawn grass naturally goes to seed. In cool-season grass lawns, seedhead production is prompted by days in excess of 12 hours long, which occurs around the middle of May. Seedhead production is heaviest when daytime temperatures are between 65° and 75°F, the weather is dry and the soil low in nitrogen. Some grass varieties produce more seedheads than others. Seedheads are most likely to be perennial ryegrass, Kentucky bluegrass, or tall fescue. Rough bluegrass and annual bluegrass, two common lawn weeds, produce seedheads in the spring. Warm-season grasses may also produce seedheads, but do so in the summer, and their seedheads are not difficult to mow. Unless they are allowed to ripen for about 4 months, seeds will not sprout, either in the lawn or in a mulch or compost made from clippings. Seedhead production weakens grass by diverting energy to making seed.
If grass is taller than usual, mow it at regular intervals, slowly lowering the mowing height until it is about 3 inches high. Do not mow lower in an attempt to halt seedhead production, but you may mow more frequently to maintain the appearance of the lawn. Use a sharp mower to avoid shredding the stems. Reduce seedhead production next year by fertilizing and watering regularly from early May through June. Nitrogen fertilizer and ample water encourage vegetative growth instead of seedhead production.