Issue 11, July 2, 2010

Common Teasel: Highway Invasive

Teasel is a frequent sight along Illinois roadways and in abandoned lots. This plant was introduced in the 1700's from Europe, most likely as an ornamental. Teasel prefers open and sunny habitats, often along roadsides and at disturbed sites. Once established in an area, teasel will crowd out native plants and reduce plant diversity. This plant is a severe threat to Illinois ecosystems; it does not take long for this plant to quickly form a monoculture that excludes all natural vegetation. Teasel plants produce over 2,000 seeds per plant and the seeds get spread by mowing along roadways. These seeds may also stay viable in the soil for at least 2 years.

Teasel starts its life cycle as a rosette (pictured right). It stays in its rosette form for about a year and then sends up a flowering stalk. The mature plants of common teasel (pictured left) are 2-8 ft tall and have oblong hairy leaves that form cups around the stem in order to catch water. Flowers are small and packed into dense oval-shaped heads with purple flower clusters that will bloom from June through October. Cut-leaf teasel blooms from July through September and produces white flowers. Leaves of cut-leaved teasel are generally broader, have feathering lobes, and the stems are prickly.

These plants send down a deep taproot and can be difficult to remove, however it is not impossible. Cutting, burning and digging are all possible methods of removal; it is important to remove as much of the root as possible to prevent resprouting. Another control method is to cut and remove the stalk of a flowering plant just before it flowers. Be certain to cut just before the plant flowers, after it has sent up a bud, or it may send up new stalks. Herbicides have also been shown to be effective. All of these methods may take several years to show results but should remove teasel, provided there is no nearby teasel spreading more seeds into the area.--Stephanie Mclaughlin, Kelly Estes

Kelly Estes

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