Know How, Know More

As you travel along Illinois highways this time of the year, you may have seen a tall, dried, spiny plant with huge showy seed heads. You might have even considered taking some seed or seed heads home to plant and use as an accent flower or for use in dried flower arrangements. PLEASE DON'T!! This invasive weed is spreading into our parks, public lands, pastures and open woodlands (savannas).

These plants are teasel, which are invasive exotic plants. Teasel was introduced into North America in the 1700's and 1800's as a way to raise the nap of cloth and as a dried flower. Until the later half of the twentieth century, its spread was localized to parts of the Northeast and Northwest areas of the USA. According to the Illinois Natural History Survey, the "rapid range expansion (of these invasive plants) probably was aided by construction of the interstate highway system."

In Illinois, we have two species of this invasive teasel family: Cut-Leaved Teasel (Dipsacus laciniatus L.) and Common Teasel (Dipsacus sylvestris Huds.). The three pictures accompanying this post are from the cut-leaved teasel, which I see every day coming to work along Illinois Route 48.

Teasel is described as biennial or monocarpic perennial. During its rosette stage, which can last longer than a year, it develops a large taproot and large basal leaves. During the flowering stage, it sends up a stalk with several seed heads that may reach over seven feet tall. Each plant will produce about 2000 large seeds. It grows well in sunny areas and likes moist to dry soil conditions.

When a mature teasel plant dies it leaves a large dead area from its basal leaves, which becomes the nursery site for new seeds shed by the plant. Seeds have the capacity to be water-dispersed, which may allow seeds to be dispersed over longer distances. Immature seed heads of cut-leaved teasel are capable of producing viable seed.

As noted by our Natural History Survey, this is a danger to our natural areas. "Teasel is an aggressive exotic species that has the capacity to take over prairies and savannas if it is allowed to become established. Lack of natural enemies allows teasel to proliferate. If left unchecked, teasel quickly can form large monocultures excluding all native vegetation. Cut-leaved teasel is more aggressive than common teasel and has severely threatened several northern and central Illinois natural areas."

Please help stop the spread of teasel in our area. For recommendations on controlling teasel on your land, please visit the Illinois Natural History Survey - Teasel website for more information.