What Is 'Overseeding' on Golf Courses?

Desert golf course in Arizona with overseeded greens and fairways.
The rough lies dormant and brown, while the overseeded fairways and greens of this golf course are vibrant green.

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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. Then, as the bermudagrass is going dormant for the winter, the ryegrass grows in.

In spring, the process is 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 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, even though they aren't—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"—an area adjacent to the real green that is mowed down to putting green-height—during the overseeding process to keep golfers from walking on the fresh and newly growing putting green grass.

Emerging Alternative to Overseeding

Overseeding a golf course requires time, labor and money, and inconveniences golfers during the grow-in times. Is there a better alternative? There might be one emerging.

Some golf courses have experimented over the years with coloring, or painting, their dormant turfgrass, rather than overseeding it. It sounds kind of silly, but as the quality of the "turf colorants" has improved, and best-practices for doing it have been shared among greenskeepers, coloring (at least of the dormant greens) is catching on with more golf courses. Overseeding is still more common for now.

A case study of the use of turf colorants published by the USGA Green Section concluded:

"The majority of golfers could not tell the difference between fairways treated with turf colorants and the conventional overseeding practices. Low-handicap players at the course especially preferred the colorant-treated playing surfaces. Turf colorants provide excellent visual definition during the winter and eliminate the poor playing conditions during the overseed transition periods. Of course, there were some golfers who were not happy with the change and preferred the overseeded fairways, but for the most part the reaction has been extremely positive."

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.