Poa annua: Australian for green
I just completed a sabbatical in Melbourne, Australia. It's a fun place with “heaps” of trendy restaurants, fine wines and great people. But it's also a strange place, too, at least to an American. The sun rises on your right and sets on your left; the constellation Orion is standing on its head; and I kept looking the wrong way for traffic. (I forgot to check which way the water turns as it goes down the drain!)
Oddities such as these served as constant reminders that I was in a foreign land. However, as a turf breeder specializing in Poa annua, there's one thing going on “down under” that seemed anything but strange to me.
POA ANNUA DOWN UNDER
As you might expect, Poa annua is a major weed of golf course putting greens and fairways in Australia, just as it is in many parts of the United States. However, a few golf course superintendents in Australia and New Zealand believe that Poa annua playing surfaces are among the best. And if nature is going to supply you with Poa in such great abundance, then why not embrace it, nurture it, give it a decent home and turn it into a benefit instead of a bane?
Annual bluegrass is known as “wintergrass” in Australia because it normally behaves as a winter annual just as it does in our Southwestern and Southern states. However, unlike the United States, where it's common practice to overseed dormant warm-season grasses in the fall with perennial ryegrass or rough bluegrass, some Australian superintendents simply use Poa annua as their naturally re-seeded winter playing surface for their bermudagrass (which they call “couchgrass”) fairways. At many Australian golf clubs, Poa annua is a desired fairway playing surface from May through November.
Superintendents regulate the amount of Poa in their fairways by the timing of a light application of non-selective herbicide during spring transition. If the Poa is a little thin one year, then fairways are sprayed after seed-head formation to ensure plenty of seed for next year. If the Poa is too thick, then fairways are sprayed prior to flowering to reduce its abundance next year.
BUT WHAT ABOUT GREENS?
With Poa annua being an important part of golf course fairways here, you might wonder whether this creates a weed problem for their greens. In fact, it does, for some.
Australia is roughly the size of the continental United States, but with a population of only 19 million. Most of these live in the eastern coastal cities of Brisbane, Sydney, Melbourne and Adelaide. Brisbane is too tropical for perennial forms of Poa annua to evolve and courses there use bermudagrass greens year-round. However, Sydney, Melbourne and Adelaide have a more Mediterranean-like climate, while Tasmania and New Zealand have a cool, oceanic, temperate climate. Thus, greens in these locations typically consist of bentgrass and most superintendents fight to keep them free of Poa, just as in the United States.
However, some Australian superintendents have welcomed the Poa onto their greens and are satisfied with the result.
BREEDING NEW POA ANNUA
The goal of my Poa annua breeding program is to provide seeded commercial cultivars of high quality Poa annua for use on golf course putting greens. After screening thousands of perennial types, I've narrowed them down to the top 12 selections. These 12 were planted as seed on golf courses in Pennsylvania, New York and California during the fall of 2001, to evaluate their performance. We also established a similar evaluation trial in Melbourne.
Australia and the United States share many of the same problems associated with Poa greens: susceptibility to anthracnose, lack of heat tolerance and seed-head production under greens height of cut. In addition, the qualities of Poa annua on greens are highly variable, both within and among golf courses. My breeding program is focused on improving many of these deficiencies of Poa. However, I believe it's the lack of high-quality seed required for putting green surfaces that is the most pressing problem right now.
We're making progress towards solving many of the former problems and it has been the support of Pennsylvania golf course superintendents, the GCSAA and the USGA that have enabled me to continue this project.
When I got to Australia, I didn't believe I would find anyone there actually using Poa as a putting surface. I was surprised to see that many superintendents have come to accept and encourage Poa as a putting surface.
In almost every region I visited, I met superintendents with nearly pure Poa greens who have no intention of switching back to bentgrass. The acceptance of Poa annua is reaching a pinnacle in Auckland, New Zealand.
At Patanuga Golf Course, where I gave a Poa workshop, I witnessed 80 to 90 percent pure bentgrass greens being lifted as sod and thrown into the compost pile. These were creeping bentgrass greens, not the Colonial or Highland types of bentgrass that can be found on minimal maintenance golf courses in these parts. Superintendent Mike Davies was replacing the bentgrass vegetatively with mini-tine cores of Poa annua collected from his old Poa greens. Davies has been able to establish puttable playing surfaces after only 6 to 8 weeks grow-in and he is on a program to re-surface all of his bent greens.
At another of New Zealand's top golf clubs, Titirangi Golf Club, Superintendent Steve Hookway has developed and perfected this technique of Poa establishment and is similarly re-surfacing his remaining bent greens to Poa.
When I gave my Poa annua workshop in New Zealand, I found that I was, essentially, “preaching to the choir.” These superintendents were doing things with Poa that I had only thought about. It seems that Michigan State's Dr. Joe Vargas had visited here about 10 years earlier and had suggested that Poa might make an excellent putting surface. Three years after that, a visit from Oregon State's Tom Cook reinforced Vargas' ideas. After Cook's visit, New Zealand superintendents began changing their management techniques to favor the Poa.
Several years ago, Steve Hookway went further and began re-surfacing his bentgrass greens to Poa. Steve has also tried something that I and another Penn State faculty member are only now beginning to play with: growing Poa greens in less than the standard 11 to 12 inch depth of a medium-sized, uniform sand profile. Four years ago, Hookway built a practice green using only 8 inches of his standard root-zone sand mix. This green has performed no differently than his other sand-based greens built to 11-inch depths.
While I wouldn't recommend this practice right now (it's a potentially risky undertaking), Dr. Andy McNitt (also of Penn State) and I are currently investigating the potential of shortening up the depths of sand-based root zones by measuring water use rates at various depths using different sized sands.
So maybe these down-under supers are way ahead me and doing things I've only begun to think about. But that's what sabbaticals are for: to learn new things. Sometimes, you find the newest things are in the strangest places.
Dr. David R. Huff is a turfgrass breeder and professor of turfgrass science at The Pennsylvania State University (University Park, Pa.).
I would like to thank all the down-under superintendents who showed me around their courses and special thanks to Brian Way and Peter Munro of the New Zealand Sports Turf Institute; John Neylan, Australian Golf Course Superintendents Association; Dr. David Aldous, Melbourne University; and Jyri Kaapro, Bayer Corp., for their persistence, patience and friendship.
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