What Is 'Overseeding' on Golf Courses?

The par five 17th hole on the South Course at the Gallery Golf Club, Dove Mountain on January , 2013 in Tucson, Arizona
When a golf course overseeds its fairways and greens but allows its rough to go dormant, it creates this tan-against-green look. Ross Kinnaird/Getty Images

In golf, "overseeding" refers to a maintenance process on golf courses in which grass seed is spread on top of the existing grass to promote new growth or to swap out seasonal turfs, replacing one type of grass with another.

Overseeding is most commonly done by courses that use bermudagrass, which goes dormant during winter months. In the fall, a bermudagrass golf course overseeds with, for example, ryegrass seed on top of the bermudagrass, timed so that as the bermudagrass goes dormant the ryegrass grows in.

In spring, the process would be reversed: Bermudagrass seed is put down on top of the ryegrass, switching the course's turf back to bermuda.

(Bermuda and rye are used as examples because the overseeding of those turfgrasses in partnership is fairly common. Various types of grasses might be involved in overseeding, but the process is most commonly used to switch a golf course over from a warm-season grass to a cool-season grass, and back again.)

Overseeding thus keeps a living, growing turfgrass available for golfers to play on.

Aesthetics of Overseeding

It should be noted, however, that some types of golf course grasses are still perfectly playable even when dormant. Those dormant grasses turn brown or tan in color, however - they look dead, in other words - and many golfers and golf course staffs don't like the cosmetics of brown putting greens.

Some golf courses overseed the tees, fairways, and greens while leaving the grass in the rough alone, which goes dormant.

This can actually create a great cosmetic appearance with the color of the green playing surfaces really popping in juxtaposition to the brown, dormant rough.

Overseeding's Effect on Play

Overseeding often involves putting the seed down along with a thin layer of sand, then allowing the new grass to grow in for many days without being cut.

So overseeding (which is sometimes done in conjunction with aeration) can, for a period of a week or 10 days or so, result in very "hairy" greens, fairways and tee boxes. Because greens with uncut grass can be difficult to putt on, some (but not all) golf courses offer green fee discounts during periods of overseeding. Some courses also use "temporary greens" during the overseeding process to keep golfers from walking on the fresh and newly growing putting green grass.

The Seed Mixture Put Down Is Called 'Topdressing'

"Topdressing" is a golf course maintenance term that describes a layer of material put down on a green for fairway following either aeration or overseeding. If the green in question is aerated, the topdressing consists of a mixture of sand, soil,​ and fertilizer. If the green is overseeded, the topdressing consists of a mixture of sand, fertilizer,​ and seed.

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