Teasel on the move

July 27, 2015 4:14 PM
Blog Post


Fig. 1.  Cutleaf teasel seedheads.

Common and cutleaf teasel are both non-native species best known for their distinctive seedheads (Figure 1).   Plants can reach heights of nearly 10 feet. Common teasel has elliptic leaves with entire margins and a 'wrinkled' surface (Figure 2.)  Cutleaf teasel leaves are deeply pinnately lobed (Figure 3).  Leaves of both species clasp the stem, forming a cuplike base that collects water.  Both species are classified as noxious weeds in Iowa.  They are often described as being biennials, but are considered monocarpic perennials. They form a basal rosette (up to 4 feet in diameter) like the biennial thistles, but they may remain in the rosette for more than one growing season.  They die after they bolt and flower.  Although there are no comprehensive surveys of their distribution within the state, I consider them to be most common in the lower one to two tiers of counties in Iowa and in the eastern part of the state.  In recent years I have observed them moving north, and recently spotted stray plants at the junction of I-35 and I-80 north of Des Moines.

The seedheads are commonly used in dried flower arrangements.  There are tales of Dutch Sylwester (Iowa's first extension weed scientist) confiscating floral arrangements at County Fairs because of the presence of teasel seedheads.  His rationale was that since teasel was a noxious weed it was illegal to use teasel seedheads unless the seed had been sterilized.  Perhaps my lack of diligence at monitoring fairs has contributed to the spread of the weed in the state.  But in all seriousness, teasel is a significant problem in roadsides, pastures, and other areas with minimal disturbance.  Many herbicides are effective against the species, best control is obtained while the plants are still in the rosette stage rather than after the stem has elongated.  Specific recommendations for control are available at the Midwest Invasive Plants Network (MIPN) Control Database.

Fig. 2.  Common teasel rosette.

Fig. 3.  Cutleaf teasel leaf axil.