 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.Each head consists of a whorl of yellow, infertile ray florets with 4 teeth at their tips, surrounding yellow disc florets that each have five long, free lobes.Adjacent each of the outer involucral bracts, several florets are fertile, and the surrounding parts of the common base of all florets in the head (or receptacle) swell and eventually become woody.