Erysimum asperum / prairie-rocket wallflower

Adjectives: alpine, biennial, disturbed, exposed, native, rocky, understory

Also known as: western wallflower
See also: Erysimum capitatum (also known as western wallflower)

---

Prairie rocket wallflower is yet another yellow (sometimes yellow-orange) crucifer, but is easily distinguished from most by the large flowers ( about ¾ inch across). Of course, like all members of the family, it has four of them. Even by comparison to other wallflowers, this one has big ones. The flowers occur in elongating clusters at the tips of stems. The flower stalks arise in leaf axils in the upper plant. The petals are rounded at the tips.

The flowers are said to have an aroma that is “slightly sweet with a touch of ammonia”. This attracts their preferred pollinators…short-tongued insects, such as flies and some smaller bees.

There are both basal and stem leaves on the plants. Basal leaves may be withered away by the time fruit set starts. They are up to 4″ long but only ½ inch wide. They are widest a bit above the middle. Each leaf has a few, widely-spaced teeth and a pointy tip. All leaves are covered in short hairs, giving them a grey-green look. The stem leaves are smaller than the basal leaves, but otherwise similar.

The fruit is a slender pod—a silique or silicle—about 3″ long. They grow perpendicular to the stems and are straight or curving slightly upward.

Prairie-rocket stems are also hairy. They are mostly unbranched, except in the flower clusters themselves, but multiple stems my arise from the rosette.

Prairie-rocket is a biennial or short-lived perennial and is considered weedy, although there doesn’t seem to be that much of it in the Valley. It grows with aspen, Douglas fir, in spruce-fir communities, and in alpine zones. Also on sand dunes, roadsides and open plains. It is not picky about the soil type.

In case you might find it interesting…  there is some argument among “that sort of botanists” concerning the difference between this and Erysimum capitatum.