Rocky ledge penstemon is unique in that it has a sub-shrub habit featuring a dense creeping mat of foliage. The evergreen leaves are bright green and have an almost succulent appearance. When it flowers, the whole plant appears covered in large purple trumpet-shaped blooms.  Naturally I missed peak flowering and just caught the tail end when I took the photos for this page... While it won't get very tall, this species can get to several feet in width.
 
This species lives in our montane and subalpine zones, and is particularly fond of rocky ledges (hence the name!) and talus piles. It appreciates a little extra water during the summer heat, but otherwise is a low-maintenance plant (like most penstemons). Although it can tolerate full sun, it will do best with some protection from intense afternoon heat.  Consider placing some rocks (football size or so) near it to provide some shade and protection. It requires well-drained soil (like a slope).  
 
Some penstemons can be short-lived if the soil is too rich. Avoid excessive compost (our native soils should be adequate). 
 
Alumroot, sticky cinquefoil, jacob's ladder, and twin arnica are all good neighbors for this penstemon.