Known by the common names Uinta Basin beardtongue and Graham's beardtongue, Penstemon grahamii is an herbaceous perennial plant within the sub genus Cristati, as documented by N. Holmgren in Cronquist and others in 1984.
Each plant has one to three stems arising from a taproot. These stems are 2.8 to 7.0 inches (7 to 18 centimeters) tall. Leaves are borne in pairs opposite each other on the stem and are of two different forms. The lower most pair, the basal leaves, are broadly oval about 0.75 inch (2 centimeters) wide and petiolate, meaning attached to the stem with a petiole. The remaining leaves, usually two to six pairs, are the cauline leaves. The cauline leaves are oblanceolate to elliptic 0.8 1.5 inches (2 to 4 centimeters long) long, 0.25 0.6 inch (0.6 1.5 centimeters) wide and are sessile, meaning attached to the stem without a petiole. Seed capsules are heart-shaped structures, approximately 0.03 to 0.04 inch (8 to 10 millimeters) in length.
All leaves are entire, meaning that they have smooth margins without lobes, and glabrous, or without hairs. P. grahamii has an inflorescence of three to 20 dark lavender or pinkish flowers, although occasionally just one or two flowers are present. Flowers have four fertile stamens and one prominent infertile staminole. Fertile statements lie along the roof of the corolla with U-shaped anthers on either side and extended about the corolla lip. The staminole is densely bearded with golden orange pubescence.
Graham's beardtongue is restricted to calcareous soils that are derived from oil shale barrens of the Green River Formation in the Uinta Basin of northeastern Utah and adjacent Colorado. This species grows on semi-barren knolls, ridges and steep slopes in a mix of fragmented white shale and silty clay soils associated with the Parachute Creek and Evacuation Creek members of the Green River Formation. It grows in sparsely vegetated communities of pinyon-juniper and desert shrub at elevations ranging from 4,690 to 6,760 feet (1,430 to 2,060 meters) and is frequently associated with pinyon pine (Pinus edulis), juniper (Juniperus osteosperma), shadscale (Atriplex confertifolia), Artemesia spp. like Wyoming bigsage and low sage, yucca (Yucca harrimaniae), Eriogonum spp. like ephedera and crispleaf buckwheat and greasebrush (Forsellesia meionandra).
Pollinators of Graham's beardtongue include the bees Anthophora lesquerellae, Osmia sanrafaelae, the sweat bees Lasioglossum sisymbrii and Dialictus sp., as well as the masarid wasp Pseudomasaris vespoides, as documented by V. Tepedino in 2005. In addition, V. Tepedino noted that a bumblebee of the genus Bombus (Bombus huntii) visits the species, as noted in L. England in 2003. The most consistent pollinator of these species is likely to be Pseudomasaris vespoides. This unusual wasp, that is a member of the only vegetarian wasp family known to science, is an extreme specialist of penstemon flowers. It collects and feeds its offspring only penstemon pollen, though V. Tepedino noted in 2005 that it may visit other plant genera for nectar.
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