Teasel (A. S. taesel, from taesan, to tease), the ripened flower heads of dipsacus fullonum, used for raising a nap upon woollen cloths. The genus dipsacus (Gr. διψέιν, to thirst, supposed to refer to the cups formed by the united leaves in some species, which hold water) is the representative of a small family, the dipsaceae, which is so closely related to the compositae that in a systematic arrangement it is placed next to that family. Like the composites, the teasel family have their flowers in dense heads, but their anthers are not united and the seeds have albumen. In the teasel itself, of which there are about a dozen old-world species, the plants are biennial or perennial, with coarse, deeply toothed, opposite, rough leaves; the branches are terminated by an oblong head, consisting of small flowers, each in the axil of a bract, which appears as a strong scale when the seeds are ripe. The wild teasel (D. sylvestris) is sparingly introduced, and is found in the older states as a roadside weed; it is from 2 to 6 ft. high, and its numerous heads of pale purple flowers, with a large involucre at their base, make it a conspicuous and not inelegant plant; the bracts to the heads terminate in a long straight point; it should be treated as an intruder.

The teasel of commerce, or fullers' teasel, though bearing the specific name given above, is generally supposed to have originated from the wild teasel, from which it differs in having a longer head with a shorter involucre; the bracts are much stiffer, and have hooked points. These heads, when ripe, are about 2½ in. long and 1½ in. in diameter, and clothed with regular, strong, sharp, recurved hooks; they are an important article of commerce, and in some countries of cultivation; considerable quantities are produced in England, but the chief supply is from Holland and France. The teasel has now and then been cultivated in this country; any good soil suits it; the seed is sown in spring, the plants thinned to 18 in. and kept cultivated through the season; the next year the flower heads appear, and earth is thrown against the plants to keep them upright; when the flowers wither, the heads are cut, leaving 8 or 9 in. of stalk attached, and dried in the sun. Their use is to tease or raise a nap upon cloth, and this is done by the hooks, which catch and pull out one end of the wool fibres, near the surface, leaving the other end of the fibre still twisted in the thread.

Formerly teasing, or teasling, was done by hand, the heads being fastened in a frame, and drawn over the surface of the cloth by the operator with a frame in each hand; now the work is done by machinery; the teasels, cut lengthwise into halves or quarters, are attached to a wooden cylindrical frame, which revolves, while at the same time the cloth passes beneath it. Much inventive talent has been expended in providing substitutes for teasels, but all have been discarded; for the natural teasel, unlike any artificial substitute, while sufficiently strong to perform the required work, will yield or break in contact with a knot or other obstacle, without injury to the cloth.

Wild Teasel (Dipsacus sylvestris), and Head of Fullers' Teasel.