Penstemon triphyllus is a member of Penstemon subg. Saccanthera sect. Saccanthera subsect. Serrulati (Bennett et al. 1987). It is unusual in having whorls of three leaves at each node. |
Bennett, R. W., K. Lodewick, and R. Lodewick. 1987. Penstemon nomenclature. Eugene, OR: American Penstemon Society.
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