It also can be a weed in vegetable crops and agronomic crops. Though present in tree and vine crops in California, it is usually not a significant problem. The genus Poa consists of about 200 species worldwide. Three members of the genus Poa are commonly found in turf.
Annual bluegrass is native to Europe but is distributed worldwide.
While the two types are not easy to distinguish from each other, the annual type is more upright in its growth habit and produces more seed than the lower-growing perennial type. The annual type also tends to produce a higher percentage of dormant seed. The perennial type produces seed that germinate readily under optimum conditions. Depending on the site there may be a predominance of one type or a mixture of both. This allows several flushes of germination at any one site throughout winter.