What does it look like?
Yellow toadflax (Linaria vulgaris Hill.) is a perennial that reproduces and spreads by creeping roots and seed. It has yellow flowers that resemble snapdragons. Stems can grow up to 1 metre tall and are rarely branched. Leaves are alternate to spirally arranged, narrow and hairless with smooth margins. Before flowering, toadflax can be distinguished from leafy spurge by snapping the stem. The absence of a milky substance in the stem will determine that the plant is toadflax.
Its weedy nature…
Yellow toadflax is a non-native plant of Eurasian origin. It is an escaped ornamental that can invade cropland, pasture, meadows and roadsides. The winged seeds disperse readily in the wind and remain viable in the soil for up to 3 years.
Creeping roots allow the plant to spread easily and form large, dense patches in a very short period of time. This weed does contain some compounds toxic to cattle and is usually avoided by grazing livestock
Tillage and chemical control practices have greatly reduced the impact of toadflax in cultivated land. In zero and minimal till areas, it is very aggressive and quickly replaces herbs and grasses. The narrow leaves and extensive root system makes toadflax a difficult weed to control.
In pasture with legumes, spot treatment with Amitrol T is recommended. A picloram product (such as Tordon) can be used with care in hay or grazing areas that do not contain legumes. Grazon can be used in native grass or forage grass pasture. Read all product labels carefully before use. Escort can also be used to suppress toadflax by visibly reducing the plant population or vigor of the plants. It should also be applied to young, actively growing weeds and as a full coverage spray for best performance.
Because toadflax is a perennial, keeping the infestation mowed will prevent seed set. However roots will spread, and therefore the plants will persist unless mowed frequently or intensively tilled in order to starve and destroy the root system. The toadflax problem may be increased if the competition is removed during frequent mowing operations.
Photographic credits to Alberta Agriculture, Food and Rural Development, the British Columbia, Ministry of Agriculture, Food and Fisheries, Field Guide to Noxious and Other Selected Weeds of British Columbia and Strathcona County, Transportation and Agriculture Services.