Penstemon attenuatus (Taper-leaved Penstemon) is a complicated species. It is one of the polyploids in the Proceri group. There are four varieties (attenuatus, militaris, palustris, pseudoprocerus), all of which may be the result of hybridization. For example, var. attenuatus has been proposed as a hybrid derivative from P. albertinus X P. confertus, var. pseudoprocerus from P. albertinus X P. procerus, and var. militaris from P. albertinus X P. globosus. These hypotheses were proposed by David Keck in his series of monographs on Penstemon published in the 1930’s, 40’s, and 50’s.
Paul Blischak will be tackling the systematics of this group as he studies the phylogeny, polyploid speciation, and role of polyploidy in ecological adaptation in section Penstemon subsect. Proceri. To whet your appetite for these interesting species, here are some photos of P. attenuatus var. militaris from Idaho.