Teasel (Dipsacus sylvestris) is a stout, tap-rooted biennial that grows up to six feet tall. The plant was introduced to North America from Europe, possibly as an ornamental or for use in wool processing. The common name “teasel” refers to the practice of using the dried flower heads to “tease” or card wool.
Teasel occurs throughout North America and is well adapted to moist, sunny habitats including prairies, savannas, seeps and sedge meadows, roadsides, railroads, and other disturbed sites. Teasel reproduces from seed, and first-year rosettes have dark green, toothed-edged leaves with a puckered surface. During the rosette stage teasel develops a large taproot that may extend more than two feet in length. Some plants produce flowers after growing for one year as a rosette, whereas others take three or more years to flower. Flowers are purple and borne in dense heads with each flower subtended by spine-like bractlets. Stems and flower heads become woody at the end of the growing season, persisting through the following winter and sometimes over several seasons. Seeds usually fall within five feet of the mother plant, although it is suggested that birds may aid long distance dispersal. An average teasel plant produces 3,300 seeds.
The most cost effective treatment for teasel is the use of selective foliar applied herbicides. Studies conducted in Missouri, Oregon and Virginia showed that Milestone® rates of 4 to 7 fluid ounces of product per acre (fl oz/A) provided good to excellent control of teasel two to three months following treatment. Teasel control was 85 percent two months following application with Milestone at 4 fl oz/A and 99 to 100 percent three months after treatment with Milestone at 5 or 7 fl oz/A. Milestone herbicide should be applied in the spring and early summer to rosettes or bolting plants to stop seed production. The higher application rate of 5 or 7 fl oz/A is recommended for plants at the bolting growth stage.
Teasel can also be controlled with digging or cultivation. In natural areas or grasslands, small infestations can be effectively removed with hand tools. Be sure to remove the root crown to prevent re-sprouting. Flowering stalks can be cut slightly below ground level just as plants start to flower. Avoid cutting stalks prior to flowering since the plants will re-sprout and flower again. Inspect sites periodically and remove any plants that re-sprout from the crown. Mowing and prescribed burning are ineffective methods for controlling teasel, and no biological agents are available for the weed.
It is important to remember that several years of treatment will be necessary to eradicate teasel from a desirable plant community. Seed production must be prevented to deplete the soil seed bank.
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Biology and management of common teasel. By Celestine Duncan. TechLine Newsletter. April 2012.