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Wild teasel produces one or more flowering stalks 2.5-6' tall, reddish- or pale green, with longitudinal ridges and scattered white prickles. The flowerhead is up to 4" tall and 1.5" across, initially egg-shaped but elongating as it matures. At the base of the flowerhead are narrow, prickly, sharply-pointed bracts up to 6" long that arch up to surround the flowerhead. Individual flowers are packed around the flowerhead like cells in a honeycomb, each flower with a 3/4" long bract that tapers to a sharp point. Individual flowers are white along most of their length, tubular, about 1/2" long, flaring out to four pale purple or lavender lobes; four stamens with white filaments and purple to lavender anthers and a single white style all protrude well beyond the end of the tube. Flowers bloom initially about halfway up the flowerhead but, later, rings of blooms develop at the base and apex of the flowerhead. Cut-leaved teasel was introduced to North America in the 18th century; the spiky flowerheads were used to comb wool and to raise the nap of (aka, "full") fabric. (Thus the species name, fullonum.) I've only seen this plant once in Jackson Park, but hope it returns (but not in excessive numbers).

Dipsacus

Dipsacus fullonum

wild teasel [Blooms: Jul-?]

Cut-leaved teasel behive-shaped flowerheads are 2-4" long and 1.5" across, spiky in every aspect. At the base of the flowerhead are 2-4" long, narrow bracts with sharp points that protrude radially. (These bracts in wild teasel, Dipsacus fullonum, arch up around the flowerhead.) Individual flowers are packed around the flowerhead like cells in a honeycomb, each flower with a 3/4" long bract that tapers to a sharp point. Individual flower are white, tubular, about 1/2" long, flaring out to four lobes; four stamens with white anthers protrude from the tube well beyond its end and there is a single style with a stigma positioned laterally at the style tip. Flowers bloom in a circle progressively from the base of the flowerhead to its tip.

Dipsacus

Dipsacus laciniatus

cut-leaved teasel [Blooms: Jul-Aug]