Polypogon is a seasonal grass first occurring in November or December. It resembles Poa annua, also seasonal, especially when it is small, so it is useful to study both of them prior to their appearance in the fall. Polypogon is fairly widespread and can be found in the Poles, Mea Mea, and No Man’s Land RAs.
Polypogon sprouts tend to have very long, slender blades, often germinating from fairly deep in sandy soil. Blades from one plant may appear like individual plants as they breach the soil surface.
At small sizes, Polypogon is often very difficult to distinguish from Poa annua. In both photos below Polypogon is on the right. In plants of similar size, Polypogon has narrower blades but is otherwise very similar. Polypogon matures much more slowly than Poa annua and at a larger size. Note that in both photos below the Poa annua is seeding.
In larger plants, Polypogon occurs as clumps of long, slender, mostly unbranched blades. The blades are soft, and usually fairly light green, especially when growing in shade. Polypogon reaches much larger sizes prior to seeding than Poa annua, and also takes a fairly long time to seed, so when it is regularly treated it is uncommon to encounter mature plants. When growing in open sandy areas the blades often branch below the surface, as in the photo below left.
Polypogon can also be very pale green, usually when growing in shaded conditions. These pale blades will often show distinct striations, similar to Setaria though of course, Polypogon blades are long and narrow compared to Setaria.