A polymorphic biennial (flowering in the second year of growth), up to 2 m tall when in flower.
Basal leaves forming a rosette.
Flowers are small, green, borne in clusters subtended by bracts, forming dense, usually branched inflorescences. Each flower contains two stigmas (female parts).
‘Seeds’ are actually fruits that are attached to each other and enveloped in a woody covering (calyces).