[2][3] Like in almost all Asteraceae, the individual flowers are 5-merous, small and clustered in typical heads, and are surrounded by an involucre, consisting of in this case two whorls of bracts, which are almost free from each other.

These heads are subtended by 2 rows of free involucral bracts, the outer 3–5 are protruding, triangular in shape, broadest and leaflike, the inner lance-shaped, ascending and may be spiny.

D. carnosa has milk sap, elliptic to linear, variably tomentose leaves, and the swollen and eventually woody segments of the receptacle containing the fruitlets are spiny.

Polymnia is however a rather unrelated plant from North America in the Heliantheae-tribe, with which it shares broad outer involucral bracts.

The French naturalist Pierre-Joseph Buc'hoz described in 1785 Breteuillia trianensis, based on a plant that was growing in the botanical garden at the Palace of Versailles.

In his Hortus Kewensis published in 1789, the Scottish botanist William Aiton reassigned P. carnosa and P. spinosa to Carl Peter Thunberg's genus Choristea.

This analysis suggests that Didelta is most related to Berkheya spinosissima, with which it shares the dimorph involucral bracts.