Toadflax

Linaria is a genus of almost 200 species of flowering plants, one of several related groups commonly called toadflax. They are annuals and herbaceous perennials, and the largest genus in the Antirrhineae tribe of the plantain family Plantaginaceae.

Taxonomy

Linaria was traditionally placed in the family Scrophulariaceae. Phylogenetic analysis has now placed it in the vastly expanded family Plantaginaceae.

Closely related genera include Nuttallanthus (American toadflaxes, recently split from Linaria), Antirrhinum (snapdragons) and Cymbalaria (ivy-leaved toadflaxes).

Cultivation

Several Linaria species are cultivated as garden plants, and some are regarded as having a weedy habit.

• Common toadflax or butter-and-eggs (Linaria vulgaris), a European species which is widely introduced elsewhere and grows as a common weed in some areas.^[1]
• Broomleaf toadflax or Dalmatian toadflax (Linaria genistifolia, syn. L. dalmatica), a native of southeast Europe that has become a weed in parts of North America.^[2]
• Purple toadflax (Linaria purpurea), a species native to the Mediterranean region grown as a garden plant for its dark purple or pink flowers. The version with purple flowers can be mistaken for lavender. Spreads readily.
• Pale toadflax (Linaria repens), a species from western Europe similar to L. purpurea, but with paler flowers.
• Alpine toadflax (Linaria alpina), purple flowers with orange (or purple) lobes in the center.
• Moroccan toadflax (Linaria maroccana), the flower has five lobes arranged into two lips with a spur at the end, often purple with white.

Species

The following species are recognised in the genus Linaria:^[3]

Etymology

The members of this genus are known in English as toadflax, a name shared with several related genera. The 'toad' in toadflax may relate to the plants having historically been used to treat bubonic plague, a false link having been drawn between the words 'bubo' and 'Bufo'. The scientific name Linaria means "resembling linum" (flax), which the foliage of some species superficially resembles.

Distribution and habitat

The genus is native to temperate regions of Europe, northern Africa and Asia, with the highest species diversity in the Mediterranean region.

Ecology

Some Linaria are regarded as noxious weeds. They are likely toxic to livestock, but ruminants generally avoid them.^[4]

Chemical composition

Linaria species are rich in alkaloids, iridoids, terpenes, phenolic acids and flavonoids.

Vasicine, Vasicinone, 7-hyrdoxyvasicine, Linarinic acid, Choline, Linavuline, Luteolin, Acacetin, Apigenin, Chrysin, Quercetin, Myricetin, Linarioside, Aucubin, Linaride, Iridolinaroside A-D, Iridolinarin A-C are some compounds found in plants of this genus.^[5]

Uses

Toadflaxes are used as food plants by the larvae of some Lepidoptera species, including the mouse moth (Amphipyra tragopoginis) and the common buckeye (Junonia coenia).

Traditional medicine

Linaria vulgaris has been used as a medicinal herb.^[6]

References