Today I'm going to start a new portion of the blog called Turf Talk. At least once a month I will post under the heading "Turf Talk", a discussion topic pertaining more towards the horticultural side of the golf course. The first topic I will cover is Poa annua or more commonly known as Poa.
What is Poa annua?
Poa annua is actually Annual Bluegrass. Unlike its "grass" name, its considered to be a noxious weed on our golf course, along with many others. Poa is a cool season, annual and perennial grass which means it germinates usually late summer to early fall when the soil temperatures reach below 70 degrees. It's identified by its boat shaped blades and its more visible seed heads. Annual Bluegrass seed head initiation can start as soon as the plant is 6 weeks old in early fall and continue until early summer. More commonly though, the seed heads will form in the spring. Annual bluegrass is a very rapid seeder. Each small plant can produce about 100 seeds in as few as 8 weeks. Viable seeds can be produced just a few days after pollination, which allows the plant to reseed even in frequently mowed turf. It has a fairly weak and shallow root system and needs available moisture to survive. It grows well in moist areas and in full sun however, it can also do well in semi-shaded and compacted soil conditions.
Why is it considered a weed?
The definition of a weed is a plant growing where it is not wanted. Poa is not wanted in the sports turf industry for the sole reason of how invasive it can be. Like described earlier, Poa can produce up to 100 seeds from one plant. Those 100 seeds produce 100 plants, which then produce 100 more seeds, which then leaves us with potentially 10,000 plants in one season all originally from one plant. Just looking at the math, one can tell how quickly this plant can spread. It's unwanted on the golf course also for it's discoloration from our desired turf such as bentgrass, ryegrass, bluegrass, and fescue. Annual Bluegrass is a very bright, light green color which stands out when the desired turfs begin to weaken or thin.
So why's it a problem on the golf course?
The ongoing issue we have with Poa is that it is incredibly hard to control. Pre-emergents and post-emergents can only do so much when a plant can germinate as quickly as Poa. With the discoloration and the very visible seed heads, it poses as an eye sore to the more seemingly aesthetic golf course. Annual Bluegrass is a cool season grass, therefore it struggles to stay alive in the heat of the summer. Only adding to the list of reasons why it doesn't fit in on the golf course. We need healthy turf in the summer! As stated before, Poa spreads rapidly and in many ways we as golfers and maintenance staff help this process tremendously. With the plant being able to germinate a viable seed within only a few days, the frequency of mowing has to be tightened to eliminate the chance of the plant to produce viable seeds. Seeds that have already been dropped can be spread by mowers, golf carts, shoes, and even a golf ball. Basically anything that the seed can adhere to, it will travel with. If seed heads are kept to a minimum and the plant can stay healthy, there really isn't any playability issue with Poa. Many greens have Poa on them but with the low height of cut its hard to distinguish the difference other than the color. If Poa is managed properly, it really creates no serious issues and can coexist with the desired turf.
We try our best! Poa is extremely hard to control and even harder to eliminate. Contributing to the difficulty is the fact that Poa comes in not only an annual species but a perennial species as well. The perennial species is what survives over winter and can deter the results from most chemical applications. We've had some success with a post-emergent chemical called Velocity and are excited to experiment some more with it this season. We do our best with collecting clippings in infested areas to eliminate the further spread of seed heads and keep a frequent and timely mowing schedule.
All in all we continue to struggle in the efforts of eliminating Poa completely from the golf course, but with the help of some new chemicals and cultural practices we have in affect, it can be controlled and slowly suppressed. Thanks for reading and check back soon for another "Turf Talk".