What kind of plant stem is soft and green?

A plant stem that is soft and green rather than woody is called herbaceous. Herbaceous stems generally lack the extensive lignification that gives trees and shrubs their rigid, persistent branches.

Many familiar plants are herbaceous, including grasses, ferns, sunflowers, peas, and numerous garden flowers. Annuals and biennials often complete their life cycles and then die back, while herbaceous perennials may lose their above-ground shoots during an unfavorable season and regrow from roots, bulbs, rhizomes, or other underground structures.

“Herbaceous” does not mean a plant is used as a cooking herb. It is a botanical description of growth form and texture. The main contrast is “woody”: a tree or shrub normally retains durable above-ground stems, while an herbaceous plant’s stem is typically flexible, green, and shorter-lived. Some botanical definitions vary at the margins, but the soft-stemmed meaning is the standard quiz answer.