Yellow toadflax (Linaria vulgaris Mill) sometimes called common toadflax or butter and eggs, resembles the snapdragon in appearance and is a member of the Figwort family. It was introduced from Europe as an ornamental and has now become a serious problem to rangeland and mountain meadows. It is a perennial reproducing from seed, as well as from underground root stalk. The stems of yellow toadflax are from 8 inches to 2 feet tall and leafy.
Leaves are pale green, alternate, narrow and pointed at both ends. The flowers are bright yellow with deep orange centers. These flowers are about an inch long and blossom in dense clusters along the stem as it lengthens and grows. The fruit is round, about 1/4 inch in diameter, brown and contains many seeds.
Yellow toadflax emerges in April and May in most parts of Colorado. It is adapted to a variety of site conditions, from moist to dry and does well in all types of soils. Its displacement of desirable grasses not only reduces ecological diversity, it also reduces rangeland value and can lead to erosion problems. Because of its early vigorous growth, extensive underground root system and effective seed dispersal methods, yellow toadflax is difficult to control.