Seedheads

Tee Off With Joe

Annual bluegrass, or poa annua, the predominant species of turfgrass on the greens, is a very tricky grass. For several reasons, it is one of the best and worst turfgrass to manage. It can tolerate very low mowing heights and can make a very nice putting surface. One of the reasons that it can give a superintendent headaches is the seeds it produces. As any golfer who has played on poa greens when seed heads are prevalent can attest, it greatly affects the playability of the greens. As a turf manager, there are a few things that I can do to minimize and strive to eliminate seed heads altogether.

First, we must understand the basics of what is happening within the plant causing the flush of seed heads. Annual bluegrass has two bio-types within the species, a true annual and a perennial. The true annual type is the most troublesome because it is the plant that produces the most seed heads in the spring. It is generally classified as a winter annual, meaning it germinates in the fall and matures in the spring. Once mature, the plant will produce seed heads before slowing its growth going into summer. Each individual poa plant can produce up to 100 seeds in 8 weeks. Without doing an extensive study to count the number of plants on a green, I can safely assume there are many thousands. That equals a lot of possible seeds produced in a short amount of time.

What do all these seed heads mean to golfers? They give the green an ugly white cast and take away from the natural green color. Secondly, and most importantly, they greatly affect ball roll. Because of the inconsistency of seed heads across the green when a golfer putts, the ball wobbles and bounces instead of rolling smoothly. This can be very frustrating because no matter how well a putt is struck, it may or may not roll truly enough to go into the cup.

To control seed heads is an art as well as a science. Timing is everything. Historical knowledge of the specific plants on a courses’ greens is very important to minimizing seed heads; poa on one course may not seed at the same time as poa on another courses’ greens. Most superintendents use Growing Degree Day (GDD) models to help predict when poa will begin producing seeds. Over the years, these models have become quite accurate. I use the GDD 32 model. The model works like this: take the high temperature for the day and the low temperature for the day, add them together, divide by two and subtract 32, anything greater than zero is a growing degree day. There are no negatives.  When the accumulative growing degree days reach a certain threshold, poa seeds will start to emerge. Based on this model, I can time my herbicide applications more effectively.

Reducing seed heads is a benefit for the long term health of the plant as well. Each plant expends a great deal of energy to produce the seed, taking away from growing strong roots. Strong roots enable the plant to take the stress of the summer months. The more seed heads I can prevent the better each plant will be at handling the heat of the summer.

With diligent monitoring of weather and a little luck, seed heads can be greatly reduced. Fewer seed heads and golfers enjoy putting and I can have stronger, healthier plants heading into the most stressful time of the year.

 

See you on the course!

Joe

jvillegas@bwrc.org