Our two species are large, coarse perennials with especially large basal leaves. In fact, the enormous leaves may at first glance be mistaken for those of Silphium terebinthinaceum.

1. Heads arranged in a more or less flat-topped or broadly dome-shaped inflorescence; peduncles 6-15 (-17) cm long..

I. helenium

1. Heads arranged racemosely in an elongated, narrow cylindrical inflorescence; peduncles 1-5 cm long.

I. racemosa