Origin:
Introduced from Europe, and now widespread in the northern United States and Canada, and as far south as Texas and throughout the western states. An extremely common winter and spring weed.
Biology:
A winter annual reproducing from seeds, and plants are capable of a heavy production of weed-blown seeds. Germination may continue throughout the spring and summer, with several generations of the weed possible in one year. Foliage and stems contain toxic alkaloids that can cause liver damage in horses and cattle, although sheep, rabbits, and goats appear resistant to the toxin.
Identification:
Mature plants can grow as high as 2 feet, and may be heavily branched and with thick foliage. Stems are weak and tend to bend with the weight of the developing flower heads. They may root at the lower nodes if these touch the soil. Leaves are alternate and generally smooth or with a few hairs. They are 2 to 3 inches long with blunt tips and jagged or deeply lobed margins. Lower leaves are on short stalks while the upper leaves join with the stem. Flower heads are extremely numerous, with many heads on stalks arising from the ends of each stem. The flower head is composed of the long, smooth bracts that enclose the yellow flowers, and they tend not to open fully, but remain tightly closed. The green bracts have black tips.
Characteristicts Important to Control:
An annual capable of germination throughout the year. Physical removal of plants is possible, but the heavy seed production leads to huge numbers of seedlings covering the ground.
