Teasel (Dipsacus Spp.) Restricted DESCRIPTION: Teasels Are Aggressive Biennials That Tend to Form Extensive Monocultures

Weed Identification and Control Sheet: www.goodoak.com/weeds WI NR-40: Teasel (Dipsacus spp.) Restricted DESCRIPTION: Teasels are aggressive biennials that tend to form extensive monocultures. Brought over from Eurasia and northern Africa for combing wool, today teasel is sometimes used in dried flower arrangements. Cut- leaved teasel (Dipsacus laciniatus) is commonly seen in the upper Midwest as opposed to common teasel (Dipsacus fullonum), which is more widely distributed throughout the United States. Teasel prefers mesic habitats that are open and sunny, but is also found on drier sites. Teasel plants can produce 2,000 seeds per plant with up to 80% of the seeds germinating. The seeds, which remain vi- able for at least two years, are often moved along highways and other right-of-ways by mow- ers and other equipment. IDENTIFICATION: The leaves of teasel are prickly, especially on the lower side of the midrib, forming cups that hold water near the stem. Compared to common teasel, cut-leaved teasel leaves are broader, divided and deeply lobed. The flowers appear at the end of the stem with a spiny head. Common teasel flowers are pale-purple whereas cut-leaved teasel flowers are white. In winter this plant is easy to identify because its dead stalk remains standing with its spiny flower head. In its first year teasel grows as a low rosette, similar to thistle or wild let- tuce rosettes. Then it grows a tall stalk and flowers, dying after dispersing its seeds. CONTROL METHODS: Organic: Teasel in its rosette stage can be dug up using a dandelion digger, but it is important to remove as much of the tap root as possible. In adult plants, using a shovel or Parsnip Predator to sever the tap root just below the soil surface works, but additional monitoring will be needed to catch resprouts. Mowing the plants just prior to flowering and then repeatedly mowing as the plants attempt to reflower is a common method for large infestations. If you are unable to mow until after flowering has completed cut stalks must be bagged and disposed of properly. Controlled burns in late spring in conjunction with other organic techniques mentioned has been shown to speed up the eradication process. Chemical: Herbicide application is most effective if done to basal rosettes in the spring and fall before the plants bolt, when the temperature is at least 50º F. Triclopyr (Garlon®, etc) and clopyralid (Transline®) are more effective than glyphosate (Round-Up®, etc.) at controlling teasel and are broadleaf specific which will prevent/reduce collateral damage of grasses and sedges. Always read herbicide labels carefully before use and always apply herbicide according to the prod- uct label. If control is necessary after the plants have bolted and formed flowers we recommend mowing them down first to prevent seed produc- tion, then applying herbicide 1-2 weeks later. NATIVE ALTERNATIVES: Since this is a full-sun weed we recommend a diverse selection of prairie species to replace and compete against thistles in order to develop a more stable and productive plant community for the site. Contact us for specific recom- mendations. All content © Frank Hassler 2015, unless otherwise noted. Updated: 10/13/15.

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