Liatris pycnostachya

Quick Characteristics:

Liatris pycnostachya Michx., the prarie blazing star, is a species mostly encountered to the west of the Mississippi very similar to Liatris spicata (which mostly grows east of it), and forms in horticulture may very often be hybrids of the two. Gaiser (1949) lists the form of the phyllaries as best defining difference, as they are acute and (slightly) reflexed in L. pycnostachya while ovoid and appressed in L. spicata. Another difference listed is a tendency to have a somewhat hirsute stem in L.pycnostachya, but that's not consistent throughout the population. For Martin Bohnet L. pycnostachia basically behaves like L. spicata "on steroids", being bigger in all parts, but again that's only partly supported by botanical literature.