In the southern U.S., annual bluegrass exists as a winter annual only.

• A. Winter annual only
• B. Summer annual
• C. Perennial
• D. Biennial

Answer: (A)

The main idea is how Poa annua, annual bluegrass, tends to behave in warm regions: it completes its life cycle during the cool season and dies off when heat arrives, so it acts as a winter annual in the southern United States. It germinates in the fall, grows through winter, and produces seeds in the spring, then declines as summer temperatures rise. This fits the definition of a winter annual, since the plant completes its life cycle within the cool-season window and does not persist into the next year.

The other life-cycle patterns don’t match this behavior here. A summer annual would start growing in spring and finish before winter, which isn’t the typical pattern for annual bluegrass in the South. A perennial would persist beyond a single growing season, surviving year after year, which Poa annua generally does not in these climates due to summer dormancy or death. A biennial would require two full growing seasons to complete its life cycle, which isn’t characteristic of this species in the southern U.S.