Yellow toadflax
General poisoning notes:
Yellow toadflax (Linaria vulgaris) is an introduced herb that is widely naturalized across Canada. This plant contains several compounds, including glucosides and the cyanogenic glucoside prunasin. The plant is regarded as toxic to livestock in Europe. Cattle generally avoid grazing stands of this plant, but there is more potential for poisoning when the animals are provided with hay that has a high content of yellow toadflax. No definitive records of poisoning are found in the literature. Other members of the genus are found in Canada as well, including the introduced Dalmatian toadflax (Linaria dalmatica). For safety''s sake, hay should not be fed to livestock if it contains a high content of these plants.
Description:
Toadflax is a perennial with erect, smooth, herbaceous stems that are less than 2 feet tall and emerge in clumps from a spreading root system. Soft, gray-green leaves, which are 1 to 1 1/2 inches long and narrow, are crowded onto each stem. Stems terminate with clusters of 15 to 20 snapdragon-like flowers that are about 1 inch long and yellow. Gently pinching the sides of a flower opens its 2 lips revealing an orange throat that acts as a guide for insects to nectar produced in the spur. The plant reproduces by seeds and creeping roots.
Root system - The root system consists of horizontal spreading roots and secondary fibrous roots.
Seedlings & Shoots - Young leaves are pale green with a powdery bloom, especially beneath. First true leaves are egg-shaped and the leaves that follow get progressively longer and more linear. Even in young plants, horizontal creeping roots form at the soil surface.
Stems- Stems are erect, leafy, 1 to 2 feet tall, and either hairless or sparsely hairy at the top. Stems may be branched, especially at the top. Multiple stems emerge from the same root system.
Leaves- Leaves are narrow, linear, soft, gray-green, and less than 1 1/2 inches long. Leaves are so densely crowded on the stem that they appear opposite (2 leaves per node) although they are alternate (1 leaf per node). Leaves taper at the base and attach directly to the stem.
Flowers- Flowers consist of 5 united petals forming a 2-lobed upper lip and a lower lip with 3 lobes that end in a long spur. Petals are yellow with an orange palate on the lower lip. Flowers look snapdragon-like and are about 1 inch long. Flowers are located at the top of stems in dense clusters of between 15 to 20.
Fruits & Seeds - Fruits are egg-shaped, 2-celled capsules filled with many blackish, disk-shaped, winged seeds. When dry, pores at the apex of each capsule open releasing seeds.
Linaria vulgaris Mill.
Nomenclature:
Scientific Name: Linaria vulgaris Mill.
Vernacular name(s): yellow toadflax
Other names: bread-and-butter, brideweed, butter-and-eggs, buttered haycocks, calve's snout, churnstaff, common linaria, common toadflax, continental flower, dead man's bones, devil's flax, devil's flower, devil's head, devil's ribbon, doggies, dragon bushes, eggs-and-bacon, eggs-and-collops, flaxweed, fluellin, gallwort, impudent lawyer, Jacob's ladder, larkspur, lion's mouth, monkey flower, patten and clogs, pedler's basket, rabbit-flower, rabbit's weed, ramstead, ranstead, toad, wild flax, wild snapdragon, wild tobacco, yellow rod, yellow toadflax.
Scientific family name: Scrophulariaceae
Vernacular family name: figwort
Geographic Information:
Alberta, British Columbia, Labrador, Manitoba, New Brunswick, Newfoundland, Nova Scotia, Northwest Territories, Ontario, Prince Edward Island, Quebec, Saskatchewan.
Toxic parts:
Leaves.
Notes on Toxic plant chemicals:
Yellow toadflax contains several chemicals, including the cyanogenic glycoside prunasin. It also contains a glucoside, antirrinoside (Sticher 1974; Conn 1981).
Toxic plant chemicals:
Antirrinoside, prunasin.
Antirrinoside
Prunasin
Chemical diagram(s) are courtesy of Ruth McDiarmid, Biochemistry Technician, Kamloops Range Station, Agriculture and Agri-Food Canada, Kamploops, British Columbia, Canada.
Animals/Human Poisoning:
Note: When an animal is listed without additional information, the literature (as of 1993) contained no detailed explanation.
Cattle
General symptoms of poisoning:
Breathing, rapid, cyanosis, dyspnea, paralysis, gait, staggering.
Notes on poisoning:
General symptoms of cyanide poisoning are listed above. These symptoms have not been reported in the literature for ingestion of yellow toadflax. The general symptoms for cyanide poisoning were taken from Kingsbury (1964).
