is quite similar to the more widespread penstemon eatonii
, the most noticeable difference being that all the lobes of the corolla open out more fully, bending by 90 degrees or more. The subulatus species also has longer, narrower flowers, narrower leaves, and non-projecting stamens. Flowers are about one inch long, gradually widening towards the tip, and opening to a two-lobed upper lip and a three-lobed lower lip; bilaterally rather than radially symmetric.
The greyish-green leaves are narrow, smooth and hairless, and may have purple edges. Those towards the middle of the stem tend to be somewhat wider around the base. Older plants may produce up to a dozen tall stems, sprouting from the base. The stems are also hairless. Fruits are hard, greenish, egg-shaped capsules, with a wavy, reddish spike at the tip.