With springtime upon us, I have been asked a lot about the Poa annua on our greens. Golfers in general are taught that Poa is a bad, less desirable putting surface and also a weed. First, let me give you a brief background. Poa annua, also known as Annual Bluegrass, is a grassy weed that invades bentgrass greens. At this point, there are no methods to selectively remove it from bentgrass. In the spring, Poa is at its worst when producing seed head. It's an ugly lime green color with a white seed head that stands out from the nice dark green bentgrass. However, in our climate, when it's at its best, there isn't a better putting surface. It's denser and has a more upright growth habit compared to bentgrass. It tolerates lower mowing heights of cut and doesn't produce thatch like bentgrass does. It grows at much cooler temperatures so it heals faster from aerification in the spring. In warmer climates, it is less desirable because it is a shallow rooted grass that has a difficult time surviving hot summers. This is why it's less prevalent in areas like Atlanta or Birmingham. Poa annua is the most adaptable grass species on the planet and can grow in a wide range of temperatures and sun light intensities. In spring, it also grows at a faster pace then bentgrass. In the afternoon, greens can become 'bumpy' due to the varying growth rates of the species of turf on the putting greens. Think back to the US Open at Chambers Bay. The greens were heavily criticized because the Poa was outgrowing the fine fescue on those greens which led to a lot of missed putts.
Since 1998 when Highlands CC opened the greens following a renovation, we've slowly but surely developed Poa annua contamination in our Penn A4 bentgrass greens. Poa loves the Highlands environment that offers mild temperatures and lots of rain (remember it's a shallow rooted grass which requires more irrigation or rain). At Highlands CC, the main reason you see it on many of our greens is simply, SHADE! Poa annua can tolerate and adapts to the lack of sunlight on greens like #1, #2, #3, #6, #7, #8, #11, #12, #15 and #16. In fact, compare the quantity of Poa on number #3 green to that on #9 green or #14 green which receive ample sunlight. The best way to prevent Poa invasion is by maintaining healthy, dense bentgrass. Unfortunately, due to excess shade, we are unable to do that on well over half of our greens. The Poa adapts to that environment and lives in areas that bentgrass simply can't survive and compete. Over time, our shade issues continue to worsen as trees grow taller and wider. In turn the Poa population continues to grow. In fact, as your Golf Course Superintendent, I often say I would never recommend regrassing our greens until the club is willing to solve the shade issues with these greens by way of tree removal. The good news however, is that Poa annua will stop producing seedhead shortly and the Poa becomes less noticeable in the greens. The green develops a more uniform appearance and, the Poa serves as one of the finest putting surfaces in the world. In short, while Poa can be an ugly issue in Spring, it serves us well on many of our greens that can't support Creeping Bentgrass growth. In another week or two, the Poa annua discussion will be a thing of the past until the spring of 2020, when it starts its reproductive cycle once again. A golf course in this climate, built in 1928, will always have its share of Poa annua. Highlands CC is a golf course that has 91 years worth genetic mutations as well as countless varieties and grass species introduced to it. While it may not be as well defined as a new golf course with new turf, it's part of what makes Highlands CC so special and gives it that old world feel that we all appreciate!
If you ever have any questions about this or any other agronomic topic, I'd love to talk to you about it!