Cascara (Rhamnus purshiana) is a tall shrub/small tree that can reach ten meters tall. It has unique, bitter but edible bark, which was used as a strong laxative by the indigenous groups of the southern Pacific Northwest. It prefers wet, shady climates, in mixed woods or swampy forests. It has alternate leaves on old growth (appears to be opposite on new growth), is deciduous but may keep its leaves over winter. The leaves are oblong to egg-shaped, six to twelve centimeters long, strongly pinnately veins and finely tooth. The veins create furrows on the shiny top of the leaf. It produces small, green-yellow flowers three to four millimeters across, with five septals stamen and petals. There can be as many as fifty in umbrella-shaped, stalked clusters near the leaves.