ScientificName: Poa Annua
Description: Annual Bluegrass germinates in early spring and late summer. It usually dies out in the heat of mid summer.
Organic Control: Use an organic preemergent in the fall and in the spring such as corn gluten meal to stop any new germination from occurring. 20% Vinegar or other acid based weed control products can kill the foliage of any currently established weeds.
Interesting Fact: No matter how often or how low you mow, Annual Bluegrass will always adjust and still be able to seed.