Plant of the Week
Western Wallflower (Erysimum capitatum)
By Walter Fertig
Mention the word “wallflower” and most people conjure an image of a shy, unassuming person, literally pasted to the wall in stressful social situations. In botanical circles, though, wallflower is the common name for a genus of mustards (Brassicaceae family) in the genus Erysimum. A common European species, E. cheiri, earned the name wallflower for its habit of growing on stone and masonry fences and walls. The name has stuck for its North American relatives, most of which grow on sandy, clayey, or rocky flats, but not vertical surfaces. Though some native species are drab in appearance, several western species have large, showy flowers and are quite conspicuous in early spring.
Western wallflower (E. capitatum) is the most widespread of the dozen native North American species. It is equally at home in montane and alpine meadows of the Rocky Mountains as it is in desert canyons of the Great Basin and Colorado Plateau. You can recognize western wallflower by its perennial growth form, densely clustered heads of bright yellow or orange, four-petal flowers that each measure up to an inch long, and its erect, narrowly elongate fruit pods called siliques. On the Great Plains, the closely related Plains wallflower (E. asperum), which differs mostly in having longer fruits that spread out laterally when mature, replaces E. capitatum. Like other wallflowers, the western and plains species have a distinctive type of pubescence on the leaves, stems, and fruits made up of small white hairs that appear flat but are actually stalks at their center, rather than being attached at the base. For crossword puzzle aficionados, these hairs are technically called malpighiaceous or dolabriform.
In Greek, Erysimum translates as “to help or save” in reference to the medicinal qualities of several species. Practitioners of European folk medicine have used wallflower poultices to relieve bronchial congestion and American Indians used dried leaves or seeds of Plains wallflower to make a tea for stomach cramps. Wallflowers are also important sources of food for wildlife, including the caterpillars of a number of butterfly and moth species.