A loosely branched shrub, covered in the spring by many white flowers. Flowers 0.8-1.3 in (3.1-7.5 cm) long, opposite, on short stalks, ovate, smooth or minutely toothed on edges. Fruit is a woody capsule. Height: 4-10 ft (1.2-3 m).
Rocky slopes and open banks in open pine woods and mixed woodland.
British Columbia to central California; east to western Montana.
Idaho's state flower, the species name (and one of its common names) honors Meriwether Lewis, who first discovered and collected it. Indians used its straight stems in making arrows.