[5][6] The genus long included only the single species B. plumosa, which was divided into two subspecies.

Studies of the plant indicated that the subspecies had low interfertility, rarely interbreeding when growing together.

[7] These are annual herbs varying in height from 10 centimeters (4 inches) to over 1.8 meters (6 feet).

The hairy, glandular phyllaries grow close to the ray florets and can remain attached to the fruits they bear.

The deeply lobed ray florets are usually whitish, often with red or purple nerves along the undersides.