Understanding the Poa annua life cycle

Poa annua is an interesting species because this plant can be considered a weed or form contiguous stands of desirable turfgrass. A new Crop Science review explores the current understanding of the P. annua life cycle along with taxonomical discrepancies and knowledge gaps.

Although the Latin name annua indicates P. annua has an annual life cycle, thousands of perennial ecotypes have been identified with variable morphology. Despite nearly 50 taxa described in literature, only two are used readily in turfgrass research: P. annua var. annua and P. annua var. reptans. With more than 50 taxa of P. annua catalogued, the use of only two is also impractical.

Morphological characteristics have been used to define the life cycle of P. annua in lieu of actual plant mortality data. Poa annua var. reptans is often described as perennial in that ecotypes exhibit a lateral growth habit and produce few seedheads whereas var. annua is described as annual in that it grows upright and is a prolific seed producer. Original taxonomical descriptions from the 1800s do not mention life cycle and only categorize plants based on morphology. We contend that the P. annua life cycle should not be determined by morphological characteristics that can be influenced by management.