As I've said many times... Poa annua is an opportunistic species that can adapt to just about any environment or soil condition. Here you see 2 small Poa plants growing out of one of the artificial hitting mats at the practice facility. The way Poa adapts to so many environments is the reason it is a difficult weed to control. On our greens at HCC, it adapts better to the shade compared to bentgrass. If you study the Poa population on #1 or #2 green, you'll notice considerably more compared to greens #17 or #9. The reason for this is simple. Shade creates a weakened, thin stand of bentgrass. In the thin areas, Poa annua is quick to invade and establish. As time goes on, the bentgrass is constantly out competed by the Poa annua until the green becomes a solid stand of that species.