What is Teasel?
Teasel is a highly invasive plant native to Eurasia and North Africa, currently listed as a Class B noxious weed in the state of Oregon. As a biennial plant, it usually completes its life cycle in two years, and grows in a rosette form when dormant or not yet mature. Mature plants may reach 7 to 10 feet tall and are easily identified by their egg-shaped flower heads, which are up to 4 inches long, spiky, cupped by long bracts, and can dry out and persist on the plants long after the blooms have died. Blooms form in belts around the flower heads and are purple or dark pink in color. The leaves of mature plants have distinctive bumpy or prickly surfaces, oppositely-arranged and fully clasp the stem (which is also prickly).
Why is Teasel a Problem?
Teasel, with its hundreds or thousands of individual flowers allowing each plant to produce multiple thousands of seeds, can easily form dense single-species stands where conditions are favorable, blocking out most native flora. Large, dense infestations are often seen along roadsides or waterways, indicating that transportation of seeds via flowing water, debris stuck to vehicles, and roadside mowing are likely significant dispersal methods for the plant. Infestations near waterways in particular pose a major threat to many sensitive riparian species.
Controlling Teasel
Deadheading (cutting flower heads of) teasel is one of the most effective ways of containing an existing infestation. Care should be taken to bag any cut flower heads, as the seeds held within will still readily germinate after being separated from the plant. Dispose of bagged flower heads by burning or at a landfill- do not compost. The plants are relatively short-lived, and dedicated control of seed production may eliminate or significantly reduce infestations.
Mowing is not usually an effective method of controlling teasel and will in fact worsen the infestation if flower heads are present. However, if flower heads from the previous growing season have been removed, springtime mowing when plants are just beginning to produce new flower heads can be effective. Teasel is also relatively easy to pull by hand.
When used according to label instructions, foliar applications of triclopyr or glyphosate may effectively control teasel infestations. Both chemicals are best used in early spring, before the plant has started to transition from the rosette phase to the vertical growth phase, so as to avoid allowing flower heads to develop. The next-best season for chemical application would be late fall, when the plant is drawing energy into the taproot.
Regardless of the chemical applied and season of application, it is important to understand the selected chemical and if it is allowed for use in the selected area, especially when near waterways and in areas where drips, spills and over use could contaminate surface and groundwater.
More information on teasel and its control can be found here: