Seed head development in home lawns has raised some interesting questions. Two of the most interesting questions have been:
- "What causes grass to develop so many seed heads?"
- "Can a person allow the seed heads to develop and mature to overseed a thin lawn?"
Cause of Seed Head Development in Lawns
Seed head production naturally occurs in cool-season turfgrasses, such as Kentucky bluegrass, under long-days and moderately cool temperatures. Long-day refers to plants that need a critical day length or more to flower. This day length can vary from species to species - for example, Kentucky bluegrass needs 13 hours or more of daylight to produce seed heads. Moderately cool temperatures are average daily temperatures of 65 to 75°F. The right balance of cool temperatures and long days can promote seedhead development in lawns. Dry weather can accentuate seed head development. Seed head development is also greater in those lawns that receive little or no nitrogen fertilizer. High nitrogen levels delay plant maturation and reduce seed head formation.
Can the Seed Heads Be Allowed to Develop and Overseed My Lawn?
When seed heads are allowed to mature in lawns, they do so at the expense of the lawn's health. The production of seeds requires carbohydrates. These carbohydrates are derived from other plant parts, such as the crown and rhizome. These two plant parts are important in the recovery from summer dormancy. The turfgrass plant regenerates new plants from buds on the crown and from nodes on the rhizome. This regeneration is important when the plant is injured by drought, high-temperature stress, insects, or any other type of injury to the turf. Therefore, if the plant utilizes most of its carbohydrates for seed production, it will be at the expense of the crown and rhizome, and ultimately the plant's health.
How to Manage Seed Heads
Lawns that have been allowed to grow tall and form seed heads should be mowed as soon as possible. Set the blade as high as possible, then gradually reduce the height of the grass in later mowings. The recommended cutting height for bluegrass lawns during the summer months is approximately 3 inches.
Lawns that go to seed at short heights should also be mowed to remove the flower heads. Do not mow lower than 2 to 2.5 inches to remove the seed heads. Instead, increase mowing frequency to remove the growing seed heads until they are completely removed.
It is beneficial to remove the seed head because if the grass is allowed to go to seed, energy is diverted away from spreading and towards flower and seed production. This causes the stand of grass to become less dense. A thin stand of grass is more prone to weed issues because there is more bare soil and less competition, allowing weed seeds to germinate and grow. If standard lawn maintenance practices, such as fertilization and proper mowing, don't improve the quality of the turf, home gardeners should renovate their lawn in late summer or early fall.