Meadow Blazing Star.  One of the many garden stars at Denver Botanic Garden's Chatfield gardens, this is especially favored by Monarch butterflies.  Fluffy rose-purple flowers to an an inch or more wide appear on the vertical 12"-36" stems midsummer to September.  Native from Alberta to New Mexico, this likes sandy or rocky soils on the dry side.  Rich loamy easy-livin' soils pushes too much growth leading to the dreaded flop.