plant systematics, general biology, plant morphology, writing and communicating in biology
Floristics, taxonomic treatments of genera, vegetative characteristics of grasses. Wrote treatments of 75 genera of Poaceae and 11 genera of Ranunculaceae for Great Plains Flora. Wrote several legume genera, Dalea, Errazurizia, Psorothamnus, and Marina, for Flora of North America. Wrote and edited many parts of Flora of Nebraska (with Robert Kaul and Steven Rolfsmeier).