Poa Annua Part 2 The Green Story

We hear a lot about Poa Annua infesting our greens. We also hear, from time to time, about major tournaments being played on golf courses featuring Poa Annua greens – like the 2019 US Open played at Pebble Beach. What’s up with that?Read More>>

The answer, of course, is that Poa Annua is a very good grass for golf greens in “Goldilocks” climates – where it never gets too hot – or too cold- and where there is regular moisture and damp weather-and it never gets too dry. Like Pebble Beach. However, even in the climates where it is seeded on purpose, Poa presents unique challenges.

Here’s what one well known golfer has to say about putting on the Poa greens at Pebble Beach:

“Putting on poa is very different than putting on bent…It doesn’t take much to get off line on poa. It gets a little bumpy, you happen to catch those little seed heads start popping up, bent sits down, poa perks up. And good putts look like they should go in, don’t go in. And you may pull one or push one that happens to bounce back in the hole”.

Well known golfer

The real issue with Poa, though, in our part of the world, is that Poa just does not stand up to the extremes of a continental climate. Too hot, too cold, too wet, too dry? Too bad…. dead Poa! We’ve experienced the problem with Poa whenever we’ve had a cold winter with too little snow. Like last year on numbers 1 and 13 greens.

Dead Poa

Why are bent grass greens more suited to our climate? First of all, Bent Grass goes dormant when stressed – unlike Poa which dies. Bent Grass does well in heat, in fact, it needs heat to grow. But even before it gets growing in the spring Bent Grass greens up early. Bent Grass requires less fertilizer and water and it’s easier for the greens crew to manage a watering program.

Bent grass doesn’t have to be cut as short as Poa to create a fast, true putting surface. When it’s rolled, bent grass lays flat.

How does Poa get into the greens? Here’s what Nick Christians, professor at Iowa State University has to say about it:

“[Poa] is a technically a winter annual, which means that it germinates late in the summer and into the fall, lives through the winter as a mature plant, and in the spring it produces a seed crop and simply dies.  It is better adapted to low mowing heights than most of our turf species and tends to crowd them out at low mowing heights. It can also produce seed at any time of year when it is actively growing, even at the lowest mowing heights.  ….  None of the other grasses that tolerate low mowing heights can do this.  This ability to produce seed gives Poa an ecological advantage over other grasses and it slowly takes over close-mown turf areas such as golf greens”.

So, how is Poa controlled in our new Bent Grass greens? Well, there isn’t a weed killer that selectively controls Poa and doesn’t kill other turf (there is a new product from Korea that may have potential, but it hasn’t been registered for use in Canada).

The first line of defence is Prevention – and you play a role! Poa often gets a foothold in a new green in a dead spot caused by an unprepared ballpark. So… number one item…. Fix your ball marks!

The greens crew also practices prevention by keeping the new greens firm. Lower watering gives the Bent Grass a chance to develop a healthy root system which keeps Poa at bay.

The second line of defence is to remove the Poa once it gets started. The only way to do this is by hand. The greens crew uses a fork with the two outside tines pushed back to extract a lump of Poa. The hole that gets left is about the size of a ball mark and the repair method is exactly the same.


Poa removal

A clump of Poa

Greens are a number one priority for our new Superintendent, Shawn. On many days 3 of his staff will be  assigned to hand remove Poa for 4-5 hours. If a choice has to made between weeding a sand trap and removing Poa, the green trumps the bunker.

Our grounds crew has done a great job on our greens this year, with a little help from Mother Nature. At the same time they’re taking a longer term view to ensure our investment in nw greens is protected for years to come.

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