The flowers in the Asteraceae family are in many ways the archetypical flower, the type of iconic flower we learn to draw from memory when we are children. They’re the very symbol of a flower.
But what’s common for all plants in the Asteraceae family is that their flowers are pseudanthiums, or false flowers. This means that the one flower we think we’re looking at is not one flower but rather an inflorescence with a multiplex of flowers, a so-called capitulum — or a flower head.
The three first plants pictured on this page have a type of capitulum called a radiate head, which means they have an inner center made up of disc florets and an outer ring of ray florets. The last plant pictured (at the bottom of the page) has a ligulate head, which means it’s made up of only ray florets.
Also not a flower
A Helianthus gracilentus in bloom. This one looks like it’s one flower, too, but in reality it’s a capitulum, i.e. a multiplex of flowers. Photo: Martin Høyem
Radiating
Helenium bigelovii, which commonly goes under the name of Bigelow’s sneezeweed, is another Asteraceae with a radiate head. The H. bigelovii typically has up to 20 ray florets, and can have as many as 800 disc florets. These particular specimens on the photo grow in a meadow in Southern California, in the San Gabriel Mountains at an altitude of 1,900 meter. I took the photo in mid August. Photo: Martin Høyem