Erysimum, or wallflower, is a genus of flowering plants in the cabbage family, Brassicaceae. It includes more than 150 species, both popular garden plants and many wild forms. Erysimum is characterised by star-shaped (and/or two-sided) trichomes growing from the stem, with yellow, red, pink or orange flowers and multiseeded seed pods.
Morphology
Wallflowers are annuals, herbaceous perennials or sub-shrubs. The perennial species are short-lived and in cultivation treated as biennials. Most species have stems erect, with a covering of bifid hairs, usually 25 ± 53 cm × 2–3mm in size. The leaves are narrow and fixed. The lower leaves are broad and round with backwardly directed lobes, 50–80mm × 0.5–3mm. Stem leaves are linear, entire, growing whitish with 2-fid hairs; 21–43mm × 1.5–2mm. Flower clusters grow at intervals on short equal stalks along the stem, with bright yellow to red or pink bilateral flowers. Flowering occurs during spring and summer. One species, Erysimum semperflorens, native to Morocco and Algeria, has white flowers. The flowering part of the stem ranges from 4 to 7mm. There are four pouch-shaped sepals, light green, 5–7mm × 1.5–2mm.
Etymology
The genus name Erysimum is derived from the Ancient Greek erysimon (ἐρύσιμον, Sisymbrium officinale or Sisymbrium polyceratium [wd], the hedgenettle), itself from the word eryo (ἐρύω) meaning to drag or eryso, a form of rhyomai (ῥύομαι), meaning "to ward off" or "to heal" in reference to its medicinal properties.
The common name "wallflower" derives from the plant's ability to grow successfully in loose wall mortar.
Distribution
Wallflowers are native to temperate Eurasia, North Africa and Macaronesia, and North America south to Costa Rica. Many wallflowers are endemic to small areas, such as:
E. etnense (Mount Etna)
E. franciscanum (north Californian coast)
E. kykkoticum (Cyprus – nearly extinct)
E. moranii (Guadalupe Island)
E. nevadense (the...
