Poa annua.

Turf professionals have varying reactions to it. Some manage it the same way they would any other turfgrass species. Others regard it as a nuisance weed, as a pest to be eradicated without prejudice.

When one considers how prevalent Poa is and how varied the climate is across North America, it is not surprising that opinions vary about the plant itself. Those opinions are, on occasion, accompanied by misconceptions. We outline a few of the more prevalent ones and attempt to set the record straight.

1 Poa management practices are universal regardless of the locale or climate.

Poaannua is found from the Arctic Circle to the equator, says Dr. Zac Reicher, a specialist with the Bayer Greens Solutions Team. “It is more than capable of surviving in a wide variety of climates,” he says. “This is largely due to the tremendous genetic variability of the turf species and its plasticity, or the ability to adapt to its surroundings and cultural management practices. Depending on the climate, Poa may be the best-adapted grass, poorly adapted, or anywhere in between. Furthermore, it may thrive in the summer in some areas, spring/fall in other areas, or all-year-long. Plus, every golf course has a different environment of soil types, shade and humidity. Add to this that all courses have a different level of ‘acceptable’ Poa population and/or performance, and one quickly realizes that Poa management programs vary dramatically from course to course and region to region.”

© Steve Dewey, Utah State University, Bugwood.org

2 I really don’t have that much Poa, do I?

Some turf managers, particularly those trying to eradicate Poa annua from their golf courses, are surprised to learn just how much of it they are dealing with. Jay Young, a PBI-Gordon product manager, has worked in the turf industry for two decades. “I’ve seen people who are trying to control Poa, or manage it, and they don’t really have a true sense of how much Poa they really have,” he says. “They become quite shocked at finding out how much Poa they actually have. Some of the void being left by the dead Poa is pretty unsightly and pretty large, so whereas they may have thought they may have only had 10 or 15 percent Poa, they’re finding out they had 20-30-40 percent, leaving some pretty unsightly voids in the turfgrass. Understanding exactly how extensive your Poa problem is a major key to really trying to get a grasp on and manage the problem.” It’s important that superintendents not develop a false sense of security when it comes to managing Poa, Young says. “People may tend to let their guard down a little bit,” he says. “Next thing you know, it’s a major problem because of the fact it is such a prolific seed producer.”

3 Bentgrass is always preferable to Poa.

Lehigh Country Club in Bethlehem, Pa, boasts one of the finest golf courses in the state, a William Flynn-Howard Toomey design. Director of grounds John Chassard has spent nearly four decades in the turf industry, 35 of them at Lehigh. In 1992, he regrassed his greens, replacing the Poa surfaces with bentgrass. But the Poa returned and Chessard is fine with that. “I’m probably a better Poa farmer than I am a bentgrass farmer,” he says. “A lot of it is dictated by the microenvironments on your golf course. The reason we regrassed was because we were doing a bunker restoration and the greens had shrunk somewhat. We wanted to recapture the original size. We had great greens going into that. It takes a while, especially in this climate, to really let bentgrass grow in. You need a good 12 months of growing, which is essentially a season-and-a-half, almost two seasons of growth.”

Today, Chassard and his team tend to greens that contain varying amounts of Poa. “I have a few greens that have great exposure,” he says. “They’re out in the open and they probably still have about 60 or 70 percent bent but then I’ve got greens that are low lying or in the shade. They go into winter early, they come out of winter late; they stay wetter because of where they’re at and they’re 100 percent Poa annua.

“And I got a lot of complaints because they weren’t what they were before we gassed them.”

Chassard notes that Poa will thrive in areas where other species of turfgrass will not. “The biggest thing with Poa – it’s going to come in and it’s going to thrive in areas where you can’t grow anything else, like bentgrass,” he says. “If you have good exposure, good air movement, great internal drainage, bent is going to do just fine, and it’s a good grass. But on old soil-based push-up greens with no internal drainage, poor air movement and lack of sunlight, Poa is going to thrive.”

4 It’s possible to completely eradicate Poa annua from a cool-season golf course.

This goal is unrealistic, says Reicher. Poa annua is a prolific seed producer, producing upward of 350 seeds per plant per year. Seeds remain viable for up to 16 years in the soil, so there may be up to 110 viable seeds in the soil. Poa occupies almost every niche on a golf course, but superintendents are usually limited to only focusing control methods on greens, leaving the rest of the course as a potential “Poa nursery.” “Bottom line is that it is impossible to eradicate Poa from a cool-season golf course, but you can prioritize your areas and maintain it at a level reasonable for your course, geography and budget,” he says. There are a number of quality products on the market to control Poa, including Velocity, Prograss and a number of plant growth regulators. But Reicher is quick to point out that chemistry has its limits. “Even an unimaginable 99 percent control in a given area would still allow many plants to continue reproducing,” he says.

5 Poa is an issue only on greens.

In sections of the country where Poa is considered an intrusive weed, superintendents trying to eradicate it understandably focus their attention on their greens. But Young cautions not to ignore tees, fairways and rough areas. “There is such an emphasis on managing Poa in greens that the rest of the golf course can of gets forgotten at times,” he says. “To have a very effective Poa management program you’ve got to manage the entire golf course, not just the greens and tees. Poa can be very easily tracked in from the fairways and the rough surrounding the greens.”

6 You can’t maintain Poa in hot, humid weather.

Superintendent Fran Owsik has spent 20 years at Lakewood Country Club in Lakewood N.J., tending to a Walter Travis design that dates back to 1919. Owsik, a longtime New Jersey turf manager, has seen plenty of Poa. He maintains it can survive the heat if it’s maintained properly. “If you’re going to survive with Poa greens, you have to have a good root system,” he says. “We aerify sometimes three times a year to establish a good root system going into June, July and August.” Managing Poa in the heat requires maintaining a balance between using enough water to keep the turf alive but not so much the root system is overwhelmed, Owsik says. In those circumstances superintendents must not overwater and in the process “cook the root system,” he adds.

Annual bluegrass (Poa annua)
Ohio State Weed Lab , The Ohio State University

7 Poa requires more water than other species of turf

In a January 2013 GCI article, the University of Minnesota’s Brian Horgan, addressed the topic. “Poa, like most grasses, can be conditioned to grow based on the management style,” he says. “So, if you give Poa too much food or too much water, the Poa will soon require the input. Light and frequent irrigation programs will confine roots to shallow depths and when the water is turned off for a day, the Poa dies. Hence the myth, Poa needs light/frequent application of water.” In fact, this approach can lead to overwatering, which weakens the root system and leaves the plant vulnerable to heat stress. Young says that superintendents working to control Poa annua need to vary their approach. “It’s definitely essential if you’re using both pre- and post-emergent herbicides to manage Poa to rotate your chemistries, even on an annual basis,” he adds. “Poa is very resistant to some of the chemistries that are out there. So, I think it’s imperative to rotate your chemistries and make sure you’re maximizing the effectiveness of what we have currently on the market.”