Facts on Poa annua Flowering

Whether you like it or not, spring highlights the amazing ability of Poa annua to produce seed.  The ability to produce copious seed is an evasive characteristic of Poa annua's evolution of different survival strategies (Cline et al., 1993).   I think one of the most amazing characteristics of Poa annua, and also a detriment from a golfing perspective is the flowering ability of Poa annua under low mowing heights. 

Below I have provided some facts about Poa annua from a paper by Dr. Mary Lush that I think gives some perspective on the seeding ability of Poa annua.

 * Poa annua (annual bluegrass) uses 4 to 35% of its top growth (dry weight) for seed production.  As a reference, annual plants like cereals invest 20 to 50% of their top growth for seed production.

* Annual seed production on a golf green is between 150,000 to 650,000 seeds per meter squared per year (177,000 to 767,000 seeds / square yard / year).  The majority of this seed would be produced occurs from spring through early summer.

* Approximately 75,000 to 225,000 tillers per meter squared per year flower (88,000 to 265,000 /square yard /year)

* During the growing season annual bluegrass tiller mortality is roughly 100,000 tillers per meter squared per month (118,000 tillers / square yard / month).  Annual bluegrass has a strong potential for replacing dying tillers with new ones.  Obviously sustaining favorable growth through the season is critical in maintaining annual bluegrass turf.

* Annual bluegrass seed dispersal is passive.  The mechanism of dispersal is by human (animal) or equipment.  Annual bluegrass has been found where human disturbance has occurred which means it is found on all 7 continents).

References:

Cline, V.W., D.B. White, H. Kaerwer.  1993.  Ovservations of population dynamics on selected annual bluegrass-creeping bentgrass golf-greens in MN.  International Turfgrass Society Research Journal 7:839-844.

Lush, W.M. 1988.  Biology of Poa annua in a termperate zone golf putting green.  I.  The above-ground population.  Journal of Applied Ecology 25:977-988.