European or Trifid Beggar-ticks
or
Trifid Bur-Marigold
Bidens tripartita
from King's American Dispensatory
Has a smooth stem, 4-furrowed, with opposite branches, and grows from 1 to 3 feet high; the leaves are lanceolate, opposite, serrate, acuminate, slightly connate at the base; the lower ones are mostly trifid; the lateral divisions are united at the base, decurrent on the petiole; the scales of the outer involucre are longer than the head, leafy, mostly obtuse, scarcely ciliate; rays none; the achenia is narrowly wedge-form, 2, 3, or 4-awned, with downwardly-barbed margins; the flowers are terminal, solitary, consisting only of the tubular, yellow florets, surrounded by a leafy involucre. This is likewise a common weed found in wet grounds, rich fields, swamps, and ditches, from New England to Missouri.