Petasites

These are all rather thick-stemmed plants that bloom in May, unlike most composites. The cauline leaves consist of broad multi-veined modified petioles with at most a rudimentary blade. The basal leaves arise from a rhizome, are long-petioled, with broad blades ± tomentose beneath, at least when young. They expand with or after the flowers. The basal leaves are conspicuous throughout the summer, long after the stems have withered. The copious silky white pappus makes a handsome sight when the plants are fruiting in late spring. The plants are functionally dioecious, the staminate flowers without rays but marginal pistillate ones often with conspicuous though relatively short rays. Pistillate heads may have numerous rays.

1. Flowers pink-purple, all without rays; locally established as an escape from cultivation.

P. hybridus

1. Flowers creamy white, marginal pistillate ones often with rays; native.

2. Blades of basal leaves ± orbicular and deeply palmately lobed.

P. frigidus

2. Blades of basal leaves ± sagittate, pinnately veined, toothed but not lobed.

P. sagittatus

All species found in Petasites

Petasites frigidusSWEET-COLTSFOOT 
Petasites hybridusBUTTERFLY-DOCK 
Petasites sagittatusSWEET-COLTSFOOT 

Citation:

MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. November 22, 2017. http://michiganflora.net/genus.aspx?id=Petasites.