Erysimum


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. The genus Cheiranthus is sometimes included here in whole or in part. Erysimum has since the early 21st century been ascribed to a monogeneric tribe, Erysimeae, characterised by sessile, and/or trichomes, yellow to orange flowers and multiseeded siliques.

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, somewhat winged, with an indumentum of bifid hairs, usually 25 ± 53 cm × 2–3 mm in size, and t-shaped trichomes. The leaves are narrow and sessile. The lower leaves are linear to oblanceolate pinnatifid with backwardly directed lobes, acute, 50–80 mm × 0.5–3 mm. Stem leaves are linear, entire, all canescent with 2-fid hairs; 21–43 mm × 1.5–2 mm. Inflorescences are produced in racemes, with bright yellow to red or pink bilateral and hermaphrodite, hypogynous and flowers. Flowering occurs during spring and summer. One species, Erysimum semperflorens, native to Morocco and Algeria, has white flowers. The floral pedicel ranges from 4 to 7 mm. Four free sepals somewhat saccate, light green, 5–7 mm × 1.5–2 mm.

Etymology

The genus name Erysimum is derived from the Greek word 'Eryo' meaning to drag.

Distribution

Wallflowers are native to southwest Asia, the Mediterranean, Europe, Africa, Micronesia, and North America through Costa Rica. Many wallflowers are endemic to small areas, such as:
Most wallflower garden cultivars are derived from E. cheiri, from southern Europe. They are often attacked by fungal and bacterial disease, so they are best grown as biennials and discarded after flowering. They are also susceptible to clubroot, a disease of Brassicaceae. Growth is best in dry soils with very good drainage, and they are often grown successfully in loose wall mortar, hence the vernacular name. There is a wide range of flower color in the warm spectrum, including white, yellow, orange, red, pink, maroon, purple and brown. The flowers, appearing in spring, usually have a strong fragrance. Wallflowers are often associated in spring bedding schemes with tulips and forget-me-nots.
The cultivar 'Bowles's Mauve' has gained the Royal Horticultural Society's Award of Garden Merit. It can become a bushy evergreen perennial in milder locations. It is strongly scented and attractive to bees.

Ecology

Erysimum is found in a range of habitats across the northern hemisphere, and has developed diverse morphology and growth habits. Different Erysimum species are used as food plants by the larvae of some Lepidoptera species including the garden carpet. In addition, some species of weevils, like Ceutorhynchus chlorophanus, live inside the fruits feeding on the developing seeds. Many species of beetles, bugs and grasshoppers eat the leaves and stalks. Some mammalian herbivores, for example mule deer in North America, argali in Mongolia, red deer in Central Europe, or Spanish ibex in the Iberian Peninsula, feed on wallflower flowering and fruiting stalks. Erysimum crepidifolium is toxic to some generalist vertebrate herbivores.
Most wallflowers are pollinator-generalists, their flowers being visited by many different species of bees, bee flies, hoverflies, butterflies, beetles, and ants. However, there are some specialist species. For example, Erysimum scoparium is pollinated almost exclusively by Anthophora alluadii.

Defensive compounds

Like most Brassicaceae, species in the genus Erysimum produce glucosinolates as defensive compounds. However, unlike almost all other genera in the Brassicaceae, Erysimum also accumulates cardiac glycosides, another class of phytochemicals with an ecological importance in insect defense. Cardiac glycosides specifically function to prevent insect herbivory and/or oviposition by blocking ion channel function in muscle cells. These chemicals are toxic enough to deter generalist, and even some specialist insect herbivores. Cardiac glycoside production is widespread in Erysimum, with at least 48 species in the genus containing these compounds. Accumulation of cardiac glycosides in Erysimum crepidifolium, but not other tested species, is induced by treatment with jasmonic acid and methyl jasmonate, endogenous elicitors of chemical defenses in many plant species. Molecular phylogenetic analysis indicates that Erysimum diversification from other Brassicaceae species that do not produce cardiac glycosides began in the Pliocene, suggesting relatively recent evolution of cardiac glycosides as a defensive trait in this genus.

Escape from herbivory

The evolution of novel chemical defenses in plants, such as cardenolides in the genus Erysimum, is predicted to allow escape from herbivory by specialist herbivores and expansion into new ecological niches. The crucifer-feeding specialist Pieries rapae is deterred from feeding and oviposition by cardenolides in Erysimum cheiranthoides. Similarly, Anthocharis cardamines, which oviposits on almost all crucifer species, avoids E. cheiranthoides. Erysimum asperum is resistant to feeding and oviposition of Pieris napi macdunnoughii This evolutionarily rapid expansion of the Erysimum genus has resulted in several hundred known species distributed throughout the northern hemisphere.

Ethnobotanical uses of ''Erysimum''

Erysimum species have a long history of use in traditional medicine. In Naturalis Historia by Pliny the Elder, Erysimum is classified as a medicinal rather than a food plant. Erysimum cheiri is described as a medicinal herb in De Materia Medica by Pedanius Dioscorides, which was the predominant European medical pharmacopeia for more than 1,500 years. Other medieval descriptions of medicinal herbs and their uses, including the Dispensatorium des Cordus by Valerius Cordus, Bocks Kräuterbuch by Hieronymus Bock, and Tabernaemontanus’ Neuw Kreuterbuch by Jacobus Theodorus Tabernaemontanus, also discuss applications of E. cheiri. In traditional Chinese medicine, Erysimum cheiranthoides has been used to treat heart disease and other ailments. Although medical uses of Erysimum became uncommon in Europe after the Middle Ages, Erysimum diffusum, as well as purified erysimin and erysimoside, have been applied more recently as Ukrainian ethnobotanical treatments.

Selected species


  • Erysimum aetnense - Etna wallflower
  • Erysimum allionii - Siberian wallflower
  • Erysimum altaicum
  • Erysimum amasianum- Turkish wallflower
  • Erysimum ammophilum
  • Erysimum angustatum - Dawson wallflower
  • Erysimum arenicola - Cascade wallflower
  • Erysimum asperum
  • Erysimum baeticum
  • Erysimum bicolor
  • Erysimum bonannianum
  • Erysimum caboverdeanum - Cabo Verde Wallflower
  • Erysimum capitatum - sanddune wallflower, western wallflower
  • Erysimum cazorlense
  • Erysimum cheiranthoides - wormseed wallflower
  • Erysimum cheiri
  • Erysimum collinum
  • Erysimum crepidifolium - pale wallflower
  • Erysimum creticum - Crete wallflower
  • Erysimum diffusum - diffuse wallflower
  • Erysimum drenowskii
  • Erysimum duriaei
  • Erysimum durum
  • Erysimum franciscanum - Franciscan wallflower
  • Erysimum gomezcampoi
  • Erysimum hedgeanum - syn. Arabidopsis erysimoides
  • Erysimum helveticum
  • Erysimum hieraciifolium - European wallflower :nl:Stijve steenraket|see the Dutch Wiki page
  • Erysimum incanum
  • Erysimum inconspicuum - smallflower prairie wallflower
  • Erysimum insulare
  • Erysimum jugicola
  • Erysimum kotschyanum - Kotschy wallflower
  • Erysimum kykkoticum
  • Erysimum linifolium
  • Erysimum mediohispanicum
  • Erysimum menziesii
  • Erysimum moranii
  • Erysimum mutabile
  • Erysimum myriophyllum
  • Erysimum nervosum
  • Erysimum nevadense - Sierra Nevada wallflower
  • Erysimum occidentale
  • Erysimum ochroleucum :fr:Vélar jaunâtre|see the French Wiki page
  • Erysimum odoratum - smelly wallflower
  • Erysimum pallasii - Pallas' wallflower
  • Erysimum perofskianum
  • Erysimum pieninicum
  • Erysimum popovii
  • Erysimum pseudorhaeticum
  • Erysimum pulchellum
  • Erysimum raulinii - Crete wallflower
  • Erysimum repandum
  • Erysimum rhaeticum - Swiss wallflower :de:Erysimum rhaeticum|see the German Wiki page
  • Erysimum ruscinonensis
  • Erysimum scoparium - Teide wallflower
  • Erysimum semperflorens
  • Erysimum siliculosum
  • Erysimum slavjankae
  • Erysimum teretifolium - Santa Cruz wallflower, Ben Lomond wallflower
  • Erysimum wahlenbergii
  • Erysimum wilczekianum
  • Erysimum wittmanii

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