This section is from the book "A Manual Of Weeds", by Ada E. Georgia. Also available from Amazon: A Manual Of Weeds.
Wild Snap-dragon, Flax-weed, Impudent Lawyer, Ranstead.
Introduced. Perennial. Propagates by seeds and by rootstocks.
Time of bloom: June to October.
Seed-time: August to November.
Range: Nova Scotia to Manitoba, southward to Georgia and Nebraska.
Habitat: Fields, pastures, roadsides, and waste places.
A weed very difficult to suppress because of its deep, running rootstocks. Cattle dislike its taste and odor, and in pastures it is left to reproduce itself unmolested; seed-bearing plants are frequently transported in baled hay.
Stems several from the same root, erect, smooth, very slender, one to two feet tall, simple or with few branches. Leaves alternate, pale green, linear, entire, pointed at both ends, sessile, crowded on the stalks. Flowers in dense racemes, the earliest clusters terminal, later bloom springing from the axils; corolla yellow, irregular, about an inch long, spurred at the base, two-lipped, the upper one two-lobed and erect, the throat nearly closed and yellow-bearded within, the bulging palate deep orange above spreading lower lips; stamens four, in unequal pairs, included; the flowers have an unpleasant odor. Capsules two celled, ovoid, each containing fifty to sixty flattened, rough, wing-margined seeds. (Fig. 264.)
If the area infested is small, use one of the strong herbicides, such as hot brine or caustic soda, which will kill all other plant growth as well but will leave the ground clean when the chemical has leached away. Do not use a cultivator in ground befouled with Toad-flax; it only serves to spread the weed; hoe and hand-labor are more effective. If the plants are kept persistently and deeply cut throughout the growing season, the underground stems will finally starve to death.
Fig. 264.-Yellow Toad-flax (Linaria vulgaris). X 1/4.