I'm a little obsessed with penstemons: the beautiful flowers, the evergreen foliage, the antics of bees bumbling in and out of the long tubular corollas, and waxleaf penstemon is a top specimen in these regards. It's showy as heck in bloom, with short wands of densly packed sky-blue flowers and the foliage is an interesting waxy grey (hence the name).
Waxleaf penstemon wants low water and full sun, thriving in exposed droughty locations. It doesn't want a slew of aggressive or overly large companions. It would do well with some bunchgrasses, hairy golden aster, twin arnica, and shaggy fleabane (to name a few).
Some interesting history on this plant:
I haven't seen it personally in the Missoula valley, however according to historical herbarium records it used to grow all over Fort Missoula (incidentally also a prime bitterroot gathering area for the Salish living in the Bitterroot Valley). In the 1930's, a botanist noted that waxleaf penstemon was "abundant on the island under the Higgins Ave bridge." There isn't an island there anymore, so....yeah.
Let's bring waxleaf penstemon back!!
2nd photo credit: Matt Lavin from Bozeman, Montana, USA, CC BY-SA 2.0, via Wikimedia Commons