Golf courses are often judged based on how they look and are designed, but just below the surface of high-quality putting greens is a secret to maintaining the rich, lush grass: aeration.
Greens that have been aerated are known as punched greens because the aeration process involves using a machine that punches down into the putting surface and pulls up a small core of the earth, leaving behind a small hole about a quarter-inch to a half-inch across, which helps circulate air down to the grassroots, keeping it full and healthy all season long.
Greens that have just been punched will have hundreds of these small holes, typically spaced from one to two inches apart, are called punched greens and are avoided by amateurs and professionals alike because this rough surface creates small obstacles for the short-range putts required to sink the ball in the hole and score for the round.
What's the point of punching the greens? The short answer is that aerification enriches the soil and allows the grass to "breathe," which makes for lusher, thicker putting greens that can be trimmed down perfectly to provide a smooth surface for short-range putts.
Punching the green, as the process is often called, counters the tendency of the soil on putting greens to compact over time and circulates air down into the soil and to the grassroots, helping keep the turfgrass healthy; punching the greens, therefore, is a maintenance practice at golf courses.
Before each tournament on the PGA Tour, the putting greens must be punched well in advance to ensure full growth and ample time for the maintenance crews to trim the fresh, healthy grass down to regulation height and for the rough, bumpy holes to naturally fill in.
Those little holes can make for a bumpy, bouncy putting surface until the green heals, so punched greens are not popular with golfers, even though the process is beneficial to the golf course.
Some golf courses offer discounts to golfers in a week or two following the punching of greens while the grass is still healing and maintenance crews haven't yet smoothed the surface of the putting green; other times, though, local clubs may institute special rules for putting greens that are particularly rough, allowing for players to take a relief from an aeration hole on the green.
There are many different names used for punched greens, so if you are venturing to a new area and listening for announces about the conditions of the course, you should look out for the phrases aerated greens, aerified greens, cored greens and plugged greens — which all refer to the same rough surface which will make your puts all the more difficult.
Courses typically punch greens in the early spring, before the first round of the PGA Tour begin, then again mid-season, usually after a major championship to avoid presenting cored greens during a professional tournament.