Linaria vulgaris (common toadflax, yellow toadflax, or butter-and-eggs) is a species of toadflax (Linaria), native from Europe to Siberia and Central Asia. It has also been introduced and is now common in North America.
It is a perennial plant with short spreading roots, erect to decumbent stems 15–90 cm (6–35 in) high, with fine, threadlike, glaucous blue-green leaves 2–6 cm (3⁄4–2 1⁄4 in) long and 1–5 mm (0.04–0.20 in) broad. The flowers are similar to those of the snapdragon, 25–33 mm (0.98–1.30 in) long, pale yellow except for the lower tip which is orange, borne in dense terminal racemes from mid summer to mid autumn. The flowers are mostly visited by bumblebees. The fruit is a globose capsule 5–11 mm (0.20–0.43 in) long and 5–7 mm (0.20–0.28 in) broad, containing numerous small seeds.
The plant is widespread on rural spots, along roads, in dunes, and on disturbed and cultivated land.
Because the flower is largely closed by its underlip, pollination requires strong insects such as bees and bumblebees (Bombus species).
The plant is food plant for a large number of insects such as the sweet gale moth (Acronicta euphorbiae), mouse moth (Amphipyra tragopoginis), silver Y (Autographa gamma), Calophasia lunula, gorgone checkerspot (Charidryas gorgone carlota), toadflax pug (Eupithecia linariata), satyr pug (Eupithecia satyrata), Falseuncaria ruficiliana, bog fritillary (Boloria eunomia), Pyrrhia umbra, brown rustic (Rusina ferruginea), and Stenoptilia bipunctidactyla.
It may be mildly toxic to livestock.
Seeds of the common toadflax, were identified from the Hoxnian interglacial strata at Clacton. Records have also come from the Weichselian glaciation strata in Essex, Huntingdonshire, Surrey and North Wales. This evidence makes the native status of the plant in Britain quite evident despite the very strong association that it has today with waste places and man-made habitats.
While most commonly found as a wildflower, toadflax is sometimes cultivated for cut flowers, which are long-lasting in the vase. Like snapdragons (Antirrhinum), they are often grown in children’s gardens for the “snapping” flowers which can be made to “talk” by squeezing them at the base of the corolla.
The plant requires ample drainage, but is otherwise adaptable to a variety of conditions. It has escaped from cultivation in North America where it is common on roadsides and in poor soils, where it has now naturalized in many U.S. states and Canadian provinces.
Medical use
Despite its reputation as a weed, like the dandelion, this plant has also been used in folk medicine for a variety of ailments. A tea made from the leaves was taken as a laxative and strong diuretic as well as for jaundice, dropsy, and enteritis with drowsiness. For skin diseases and piles, either a leaf tea or an ointment made from the flowers was used. In addition, a tea made in milk instead of water has been used as an insecticide. It is confirmed to have diuretic and fever-reducing properties.
Linaria acutiloba Fisch. ex Rchb. is a synonym. Because this plant grows as a weed, it has acquired a large number of local colloquial names, including brideweed, bridewort, butter and eggs (but see Lotus corniculatus), butter haycocks, bread and butter, bunny haycocks, bunny mouths, calf’s snout, Continental weed, dead men’s bones, devil’s flax, devil’s flower, doggies, dragon bushes, eggs and bacon (but see Lotus corniculatus), eggs and butter, false flax, flaxweed, fluellen (but see Kickxia), gallweed, gallwort, impudent lawyer, Jacob’s ladder (but see Polemonium), lion’s mouth, monkey flower (but see Mimulus), North American ramsted, rabbit flower, rancid, ransted, snapdragon (but see Antirrhinum), wild flax, wild snapdragon, wild tobacco (but see Nicotiana), yellow rod, yellow toadflax.