How can sedges be best described?

Sedges are best described as perennial plants with triangular, jointless stems. This characteristic is a distinguishing feature of sedges, which belong to the family Cyperaceae. The triangular stems set them apart from grasses, which typically have round stems, and from rushes, which have round or cylindrical stems but do not have the same distinctive triangular shape. The jointless aspect of the stems further emphasizes their unique structure.

In contrast, while some sedges may indeed possess broad leaves or cylindrical stems, the defining features are primarily their perennial growth habit, triangular stem structure, and the fact that they often thrive in wetland or marginal habitats. The other choices incorrectly emphasize features that do not characterize sedges specifically, thus highlighting why the identification as perennials with triangular, jointless stems is accurate and important for recognizing this group of plants.