Northern Prairie Wildlife Research Center
To date found only in southeastern North Dakota, threetooth ragwort ranges from Manitoba to Texas west to the uplift of the Rocky Mountains at elevations under 9,000 ft.
Threetooth ragwort is perennial from a terminally branched taproot. Plants are usually 6-12 inches tall and may have patches of loose wooly hairs when young. Leaves are mostly basal, spoon-shaped, and toothed toward the tips. They are about 1 1/2 inches long and have a petiole about the same length. The few stem leaves are much smaller and more deeply incised. One to several stems bear about 4-12 flower heads about 1/2 inch wide. As in all our Senecios, the flowers are yellow. Fruits are cylindrical, ribbed achenes.
Look for threetooth ragwort in May or June in dry sites on native grassland. More plants seem to occur where grazing pressure is substantial. Many Senecios, including several trees, are used economically worldwide as medicines, foods, and ornamental woods. Others poison horses and cattle. However, I could find no mention of threetooth ragwort in these regards.
Ragworts (also called "groundsels") are members of the sunflower family (Asteraceae). In this family, many flowers are often arranged into flower heads that are often mistaken for a single flower. The family contains over 15,000 species, more than in any other family in North Dakota as well as in most countries in the North Temperate Zone.
Senecio is an immense, worldwide genus of over 1,000 species, the name derived from the Latin senex, "an old man," likely in reference to the pale or gray appearance of many species. The Senecios are often called "groundsels." The specific epithet tridenticulatus means "three-toothed" in botanical Latin. Threetooth ragwort was described for science by the Swedish-born American botanist and curator of the New York Botanical Garden, Per Axel Rydberg (1860-1931).