Source: Idaho's Noxious Weeds by Robert H. Callihan & Timothy W. Miller
BACKGROUND
Yellow toadflax (Linaria vulgaris) is likely an escaped ornamental brought to this country from Europe. It spreads both by seed and roots. This weed contains a poisonous glucoside that may be harmful to livestock. Yellow Toadflax grows under a wide range of environmental conditions.
DESCRIPTION
Yellow toadflax is a perennialPlant that lives for more than 2 growing seasons with narrow, nearly oppositeLeaves situated directly across the stem from each other, 2-inch long leaves. Stems are smooth, generally unbranched, and up to 3 feet tall. The showy snapdragon-like flower are about 1 inch long(excluding the ½- inch spur), yellow with an orange throat, and are borne in midsummer and fall. Seed is produced in brown, globe-shaped capsules. Seeds are round and dark colored with notched, papery collars that act as wings in spreading the seed.
DISTRIBUTION
Yellow toadflax is found throughout the U.S. and in nearly all areas except western and southcentral Idaho counties.
CONTROL
Biological control agents (a defoliating moth, a seed head weevil, and a flower beetle) provide from fair to good control of yellow toadflax. Herbicides are also available.