Dipsacus fullonum, syn. Dipsacus sylvestris, is a species of flowering plant known by the common names wild teasel or fuller's teasel, although the latter name is usually applied to the cultivated species Dipsacus sativus. It is native to Eurasia and North Africa, but it is known in the Americas, southern Africa, Australia and New Zealand as an introduced species and often a noxious weed. It forms large monocultures (displacing other species) in areas it invades that have favorable climates and none of its biological control species. The inflorescence is a cylindrical array of lavender flowers which dries to a cone of spine-tipped hard bracts. It may be 10 centimeters long.

D. fullonum is identifiable in the 6th-century Vienna Dioscurides, fol. 99
It is a herbaceous biennial plant (rarely a short-lived perennial plant) growing to 1–2.5 metres (3.3–8.2 ft) tall.

Two moths useful for biological control were tested in Slovakia in 2003-2004 (following the identification of seven insects associated with the plant and their consideration), including the monophagous Endothenia gentianaeana. Although Endothenia gentianaeana was able to be reared in high numbers and its presence was found in nearly 100% of teasel plants surveyed in Slovakia, and despite the high level of damage caused by the second moth, Cochylis roseana (which was not targeted by local parasitic wasps frequently as was Endothenia gentianaeana), the USDA has not approved either of these moths for introduction as of February 2018. Instead, the USDA continues to suggest the use of herbicidal chemicals.

Description
The genus name is derived from the word for thirst and refers to the cup-like formation made where sessile leaves merge at the stem. Rain water can collect in this receptacle; this may perform the function of preventing sap-sucking insects such as aphids from climbing the stem. A recent experiment has shown that adding dead insects to these cups increases the seedset of teasels (but not their height), implying partial carnivory. The leaf shape is lanceolate, 20–40 centimetres (7.9–15.7 in) long and 3–6 centimetres (1.2–2.4 in) broad, with a row of small spines on the underside of the midrib.

Teasels are easily identified with their prickly stem and leaves, and the inflorescence of purple, dark pink or lavender flowers that form a head on the end of the stem(s). The inflorescence is ovoid, 4–10 centimetres (1.6–3.9 in) long and 3–5 centimetres (1.2–2.0 in) broad, with a basal whorl of spiny bracts. The first flowers begin opening in a belt around the middle of the spherical or oval flowerhead, and then open sequentially toward the top and bottom, forming two narrow belts as the flowering progresses. The dried head persists afterwards, with the small (4–6 millimetres (0.16–0.24 in)) seeds maturing in mid autumn.

Source
Wikipedia