Oct. 15, 2020

Aster family flower types

The type of flower head in the aster family helps determine which subfamily a species belongs to. Flowers with radiate heads only occur in one subfamily. However, that doesn't mean that all flowers in the subfamily are radiate. Big Devil beggar's-ticks is one such. Many flowers in this genus, Bidens, have rays. Many do not. Identification keys have to adapt to that feature, leading us to Bidens through two separate lines of choices, one for each type of flower head.