We have recently received winter grass samples for identification and one of the most common has been Annual Bluegrass (Poa annua). Native to Europe it is distributed worldwide we find it invading homeowner landscapes, golf courses, and agricultural fields. It reproduces only by seeds¹ and can have several generations per year. The leaf blades are about 3 in long and plants are about 4 to12 inches tall. The flowering part is about 1to 4 inches long There are several species of the genus Poa but we included in this article the most typical characteristics of the Poa annuaspecies³.
Please check the highlighted features of this grass in the illustrations below:

1. The leaf blades end in a boat shaped tip.
2. The ligule is membranous.
3. Flower head outline looks like a triangle
4. Auricles are absent
5. Collar narrow and smooth

When leaves are looked through light two transparent lines on both sides of the midrib can be seen ²

Figure1. Key characteristics of annual bluegrass. (Images: M. Peña and Jim
Converse Proturf Guide to the Identification of grasses).


Figure 2. Proturf Guide to The Identification of Grasses, Jim Converse

References:

1. Parker, K. F. (1972). An Illustrated Guide to Arizona Weeds. University of Arizona Press.
2. Read more at: https://www.turffiles.ncsu.edu/weeds-in-turf/annual-bluegrass/
3. https://ipm.ucanr.edu/PMG/PESTNOTES/pn7464.html