is one of the tallest non-shrublike flowering plants of the western mountains, sometimes exceeding six feet. The stout, rigid, unbranched stem and the long, clustered green leaves are generally hairless but may have a fine, soft hair covering. The lance-shaped stem leaves are arranged in whorls, of three to seven, and they have pointed tips; basal leaves are more oblanceolate in shape, generally with rounded tips.
Flowers are produced in clusters nearly all the way along the stem, attached by pedicels (up to four inches long) growing from the leaf nodes; they become more dense towards the top of the plant. Flowers have a greenish-yellow, four-lobed corolla, sometimes streaked with purple, above a light green calyx which is divided into four thin lobes, extending beyond the corolla. Each corolla lobe is marked by two small, fringed nectar pits.
This species flowers only once, after growing for several years; it dies at the end of the blooming period.