Issue 10, July 14, 2014
Now is the time of year when teasel can readily be spotted while traveling interstates and highways. Common teasel (Dipsacus fullonum) is an invasive monocarpic perennial - which means it can take a minimum of one year to flower and once it does, it dies. Teasel is native to Europe and is believed to have been introduced into North America accidentally by catching a ride on other plant materials. It has spread rapidly over the last twenty to thirty years. It grows best in sunny open areas such as prairies, savannas, seeps, meadows, roadsides, dumps, or disturbed areas.
Before flowering, the plant grows as a rosette. The duration of the time teasel spends as a rosette depends on how long it takes for the plant to take in enough resources and nutrients to produce the flower. During the rosette stage the plant has ovoid shaped leaves and develops a large tap root. The tap root can grow to be over two feet long and one foot in diameter. Once the plant has collected enough nutrients, the plant will send up shoots to flower. Common teasel usually blooms in June through October. The flowers are small, purple, and clumped in dense oval shaped heads. The flowered stem may reach up to six or seven feet. The flower head is surrounded by long upward curving bracts that come up from under the flower head. In this mature stage the leaves are opposite and sessile and become more oblong and hairy while the stem becomes prickly.
Another species of teasel is the cut leaved teasel, which has white flowers and is much more aggressive. The best ways to manage teasel is to dig it up or cut it off. The more tap root you dig up, the more likely you are of killing off the plant. Another alternative is to cut off the flowering stalks after they bloom and dispose of their heads; the seeds will continue to develop even after the stalk has been cut off. It is important not to cut the stalk off before it flowers because it will just send up another flower stalk. Herbicides have also been shown to be effective.
If you spot teasel in your area, please consider reporting any new finds to www.eddmaps.org. (Evan Cropek and Kelly Estes)