The Q and A on P-O-A

The word Poa probably brings an image to mind. To many golfers it’s the grass that makes the greens bumpy every spring. To golf course superintendents, it can be the unreliable turf that has to be nursed through the summer heat.

Bad stuff, right? But wait a minute. Isn’t Poa the turf on some of the most famous putting surfaces in the world, such as Pine Valley, Oakmont, and Pebble Beach? At Laurel Creek, #17 has the highest percentage of Poa, yet many players say it’s one of the smoothest greens we have. Clearly this must be a wonderful variety of grass!

Confusing? Perhaps a closer look at this grass will shed some light on the different perspectives. There are many types of Poa Annua, also known as Annual Bluegrass. In fact, over 500 different cultivars of Poa have been identified. So, one might say that there is “good” Poa and “bad” Poa.

Although it is all referred to as Annual Bluegrass, many of the better performing bio-types are now considered perennial in nature. This perennial Poa has extremely high shoot density, and produces little seed. Just like a tightly woven fabric, the finer the leaf blade and the greater the number of shoots per square inch, the smoother and faster the greens.

Okay, you say, I’m sold on Poa—why wouldn’t everybody want it at their course? Well, the downside to Poa is that there is also the true annual type, which tends to be the first to show up at golf courses. This type of Poa seeds in the spring, providing bumpy conditions. Once the seeding is finished, Poa is susceptible to several insects and turf diseases that Bentgrass is not, and Poa has a relatively short root system, making it prone to wilting in the summer.

So if Poa has all of these problems, how does it out compete Bentgrass in the first place? Remember those seedheads that your ball bounces across in the spring? Poa’s survival mechanism is its ability to produce voluminous quantities of seed. After a few years, the soil contains what is referred to as a seed bank of Poa which can germinate after the late summer aerification. The only certain way to remove this seed bank of Poa is to apply a soil fumigant to sterilize both the green’s surface and the soil beneath. This process was undertaken at Tavistock during their renovation.

Can Poa be stopped from encroaching on Bentgrass? Going back to June, 2000, our USGA Turf Advisory Service Report answered this question by referring to it as, “…the inevitable onslaught of Poa Annua.” At this time, the USGA’s recommendation is for us to manage Poa on our 24 year old greens, rather than trying to eliminate it. This involves the application of different plant growth regulators to minimize seedhead development and help to match the growth rates of the Poa and Bentgrass.

Because of the desirable traits of the perennial types of Poa, such as a high shoot density and lack of seedheads, Dr. David Huff of Penn State has undertaken a breeding program to develop cultivars that could be used on golf course putting greens. However, in an ironic twist, the best performing Poa doesn’t seem to produce enough seed for commercial production.

Well, regardless of what you call it—Poa Annua, Annual Bluegrass, or just plain Poa, given the number of varieties and their different characteristics, this is clearly one plant that can’t be pigeon-holed into the strict categories of preferred or unwelcome.

During much of the year, Poa can provide a smooth putting surface.