Overseeding is the process of planting new grass seed directly into existing turf without removing the base layer. This practice is fundamental to golf course maintenance, ensuring playing surfaces remain green and consistently playable throughout the year, especially in regions with distinct seasonal changes. Superintendents use this technique to maintain the high standards of aesthetics and playability expected from a facility.
Maintaining Green Turf Through Seasonal Transition
The core reason for overseeding is managing the natural transition between warm-season and cool-season grasses. Courses in warmer climates, such as the Southern United States, typically use warm-season turf like Bermuda grass, which flourishes in high temperatures. When temperatures drop in the fall and winter, Bermuda grass naturally goes dormant, turning brown and ceasing growth.
To maintain a dense, high-quality playing surface, cool-season grass is introduced. Perennial ryegrass is the most common choice for overseeding because it thrives in the cooler temperatures that cause the underlying Bermuda grass to become inactive. This process ensures continuous green coverage and a resilient surface that can withstand the wear of winter play.
The Mechanics of Applying New Seed
The overseeding process begins with precise preparation of the existing turf. The first step involves mowing the warm-season grass extremely low, a process often called scalping. This close cut removes excess leaf material and reduces competition, ensuring the new seeds have a better chance of survival.
Following scalping, the turf manager prepares a proper seedbed to maximize seed-to-soil contact, which is necessary for germination. Equipment such as verticutters or slicers may be used to lightly open the turf canopy and expose a small amount of soil. This mechanical cultivation helps the seeds settle into the ground rather than resting on top of the existing grass. Aeration may also be performed to relieve soil compaction and improve the environment for the new seedlings.
Seed application involves spreading high-quality ryegrass across the prepared areas, including fairways, tees, and greens, using specialized spreaders. Application is often done in multiple directions to ensure uniform coverage.
Immediately after seeding, a light layer of sand, known as topdressing, may be applied over the greens to protect the seeds and help them settle. Consistent and frequent irrigation follows, keeping the seedbed constantly moist until the seeds germinate and the seedlings establish roots.
When Overseeding Occurs and Impact on Play
The timing of overseeding is tied directly to the climate and the desired onset of the winter playing season. This procedure typically occurs in the late summer or early fall, often between mid-September and mid-October, when temperatures start to drop. The goal is to allow the cool-season grass to establish itself before the arrival of a hard frost.
Because the process requires intensive preparation and watering, it necessitates temporary changes to golf course operations. Many courses will close entirely for a period, often around two weeks, to allow the new grass to germinate without disruption from foot or cart traffic. When the course reopens, golfers may be restricted to “cart path only” rules for several more weeks to protect the young seedlings.
The newly established turf temporarily affects the quality of play, particularly on the greens. The increased watering required for germination makes the turf softer, and the presence of new grass often results in slower green speeds. This period of altered conditions ensures the course remains lush and playable for the remainder of the cooler season.