When golfers hear the word “thatch”, it’s usually not a good thing. If someone describes greens as “thatchy” they’re saying the greens are soft or spongy and aren’t playing that well. We also hear thatch mentioned as a reason for putting green aeration, which isn’t exactly a favorite topic among golfers. But what is thatch and why is it such a big deal in course maintenance?

Thatch is a layer of living and dead plant material found between the green grass blades and the soil. It naturally builds up over time with leaves and stems growing, dying and being mowed. Too much thatch has a very negative impact on the health and playability of golf greens. It can cause them to become soft and soggy and allow large ball marks to form. Greens with too much thatch are also prone to scalping by mowers because the machines sink in and cut lower than intended in some spots, leaving the putting surface irregular and injured. Thatch also harbors damaging insects and turfgrass diseases, and it can make these pests harder to control – and the list of potential problems goes on! Long story short, too much thatch is bad news and unfortunately, many of the modern grasses used on putting greens are rapid thatch producers and can quickly generate excessive plant material if not managed properly.

However, having some thatch is essential for good playing conditions, so there needs to be a balance. Golf greens normally require a minimum of one-quarter inch of thatch to withstand golfer traffic and regular maintenance practices. A healthy layer of thatch also helps the green accept good golf shots and prevents them from bounding over. Some thatch also helps the grass handle summer heat stress and reduces the risk of fertilizer and pesticides washing through the soil. Maintaining a healthy thatch layer that isn’t too thick or dense and allows water and air to flow freely is the ideal, but that’s not easy to do.

Thatch accumulation is managed by properly applying fertilizer and performing maintenance practices like aeration, topdressing and verticutting. These management practices remove excess plant material, dilute the thatch layer, smooth the putting surface and encourage microorganisms to decompose thatch. If the maintenance team is given the time and resources to stay on top of things, routine thatch management won’t be that disruptive. However, if thatch gets out of control it will have an obvious negative impact on playing conditions and the problem will require more aggressive action to fix.

Next time you see the golf course superintendent checking out the greens at the course you’re playing, you can talk with them about thatch and learn more about how they are managing it to give you the best putting surfaces possible.