Which type of perennial has stems that remain above ground all year long?

The choice of woody perennials is correct because these plants, such as trees and shrubs, have stems that remain above ground throughout the year. Unlike herbaceous perennials, which die back to the ground in winter, woody perennials maintain their structure, allowing them to grow taller and become more substantial over time. This characteristic enables them to survive harsh weather conditions and regrow in the spring.

Other plant types, like herbaceous perennials, have stems that die back during the winter months and regenerate from their roots. Biennials and annuals complete their life cycles in one or two years, respectively, and do not possess the above-ground structure sustained through multiple years. Thus, woody perennials stand out as the only group that retains its stems year-round, confirming their classification.