It is a widespread plant from near timberline to the foothills in the Southern Rocky Mountains and Colorado Plateau in North America.

It is noted for its ground hugging growth habit and as a plant used in xeriscape and rock gardening.

Penstemon caespitosus is very low growing, usually just 4–5 centimeters (1.6–2.0 in) tall with the stems laying down and only the tips curving upright.

The stems root at nodes eventually forming solid mat up to 2 meters (6 ft 7 in) in width.

Like the stems they are covered in pointed backwards facing hairs, but they do not hide the green color of the leaves.

The externally the flowers are a handsome blue to purplish lavender with reddish violet nectar guides on the petal lobes into the interior.

The hairy staminode for which Penstemon are known 9–12 millimeters long and covered at the end with densely pilose bright golden yellow hairs.

[3] The first recorded scientific collection of Penstemon caespitosus was by Thomas Nuttall and is assumed to have been on his expedition to Oregon in 1834.

[1] It had also been collected by John C. Frémont during one of his expeditions, but the condition of the specimen when examined by Gray was, "poor".

[7] Botanist William A. Weber thought that Penstemon crandallii and its varieties not distinct enough to qualify as species and that it should be synonymized with P. caespitosus.

[16] Both POWO and PLANTS record this variety of P. caespitosus as growing in Utah and Arizona and being absent from the Rocky Mountains, this geographic isolation also being an argument for being a separate subspecies despite physical similarity.

[10] In this the FNA is in agreement, recording the leaves as ranging in shape from blade obovate to spatulate.

[2][3] Both POWO and PLANTS record Penstemon caespitosus in four western US states, Arizona, Colorado, Utah, and Wyoming.

[23] Mat penstemon is amenable to cultivation and is widely grown in both Europe and America as a groundcover especially in rock gardens for xeriscaping.

[26] Though more tolerant of moisture than other mat forming species it is, like most penstemons, susceptible to root rot in poorly draining locations.

[26] 'Waggon wheel' introduced in 2022 by the Plant Select cooperative sponsored by Colorado State University and Denver Botanic Gardens.