By PR Extension Office
One of the earliest weeds to appear in the spring, as early as the mustards, is a small yellow flowering annual known as bur buttercup, according to Powder River Extension Agent Mary Rumph. It is a winter annual that emerges, flowers and sets fruit when the temperatures climb into the 45-50 degree range. Plants only grow to be 2 or 3 inches tall. They often occur in dense mats which cover large areas of the ground.
Each blossom usually has 5 bright yellow petals. The flowers are tiny, measuring less than a quarter inch long. At maturity, each blossom develops into a bur, which dries and turns brown.
Bur buttercup is high-ly toxic to cattle, sheep and horses and can affect hu-mans by irritating skin and causing blisters. The plant contains ranunculin, which turns into a toxic compound protoanemonin when the plant is crushed by chewing. Signs of poisoning include anorexia, labored breathing, diarrhea, dyspnea, recumbency, weakness, and death.
It is a small, gray-green tap rooted plant with three to four deeply lobed, fine-haired leaves resembling antlers. By early summer, it scatters its seed and its burs have turned from green to straw-colored to brown. The burs, though not as sharp as puncturevine seeds, are painful if stepped on with bare feet.
Bur Buttercup primarily grows in waste areas. It is best controlled before it produces flowers and seeds. Hoeing, pulling and digging can control it; it can also be sprayed (depending on its location) with 2,4-D, Ally, Banvel, or Roundup. Contact the Powder River Extension Office at 436-2424 or Rumph at mrumph @montana.edu for more information.
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