From Great Plant Picks:
Cascade mahonia, Mahonia nervosa, is one of our Northwest native plants. This suckering shrub forms a loose groundcover with lustrous emerald leaves and panicles of canary flowers in May and waxy blue berries in autumn. It is durable and an excellent choice when the plant palette is limited to native plants. It is adaptable to difficult growing situations like parking strips and parking lot planting beds. It would look great as a groundcover for Red stemmed dogwoods, Corylopsis pauciflora, Betula albosinensis var. septentrionalis and all witchhazels. It would be excellent on steep slopes. Broken roots and stems are sulfur yellow, which is a trait of all plants in the barberry family.
 
This low growing mahonia is tough. It will grow well in full sun to deep shade. In full sun the foliage will turn an attractive plum color. It prefers a moist to well-drained soil, but will tolerate sand and clay. Once established it is drought tolerant, although plants in full sun can yellow if kept excessively dry. Occasional watering during dry weather will help plants in sun to maintain a rich green foliage color. Little pruning is necessary other than the removal of dead or broken limbs.
 
Bloom Period: Spring. Fruits ripen in autumn.
 
Primary image credit: Daderot, CC0, via Wikimedia Commons