Lack of natural enemies allows teasel to proliferate. If left unchecked, teasel can quickly form large monocultures excluding all native vegetation.
The teasel population has rapidly expanded in the last 30 years particularly along highway systems where mowing equipment aids dispersal.
Characteristics
This biennial plant grows as a basal rosette for a minimum of one year and in its second season sends up a tall flowering stalk and dies after flowering. The period of time as a rosette varies depending on how long it takes the plant to acquire sufficient resources to flower.
Previous Season’s Teasel
Leaves in the rosette are somewhat ovoid in young plants and become large, oblong and hairy in older plants. Leaves of the cut-leaved teasel are deeply lobed.
Leaf of young cut-leaved teasel plant
The cut-leaved teasel’s leaves are joined at the stem so that they form a cup that will hold water. As a rosette, teasel develops a large tap root that may become more than two feet in length and an inch in diameter at the crown.
Spiny teasel stems
Cut-leaved teasel normally has white flowers from July to September while common teasel produces purple blooms from June to October. Stiff, spiny, leaf-like structures called bracts curve up from the base of the flower head. A single teasel plant produces more than 2,000 seeds which remain viable for several years. The seeds disperse in close proximity to the parent plant but can be transported longer distances by water or on mowing equipment.
Cut-leaved teasel flower head
Habitat
Teasel grows in open, sunny habitats in from wet to dry conditions. Optimal conditions seem to be mesic. In Illinois, teasel sometimes occurs in high quality prairies, savannas, seeps, and sedge meadows, though roadsides, railroad tracks, dumps and other heavily disturbed areas are the most common teasel habitats. Teasel is often found in large stands of tall plants of similar height.
Field of teasel
Similar Species
Invasive
Bull thistle
Bull thistle (Cirsium vulgare) has longer spines. The thistle flower is above the spiny base while the teasel flower comes out of the honeycomb sections. Thistle leaves are alternate while teasel leaves are opposite.
Native
Tall thistle (Cirsium altissimum)
Pasture thistle (Cirsium discolor)
These native thistles also have alternate leaves. Native thistles aren’t very prevalent.
Control Methods
Accurately identify cut-leaved and common teasel before attempting any control measures. If identification of the species is in doubt, confirm the plant’s identity with a knowledgeable individual and/or by consulting appropriate books or websites.
Common teasel
Manual
For small populations, mechanical methods work quite well. Dig up young rosettes using a dandelion digger. As when digging dandelions, remove as much root as possible.
When the plants have sent up the flowering stalk, manual control is accomplished by:
Cutting off the flower head, being sure to do so at the proper time—when it is flowering but has not set seed. Remove flower heads and dispose of them by bagging or burning. Flowers can release seed even after they are cut.
Then cutting the plant at or below the ground level.
Monitoring the area for plants that you may have missed. Perform a later inspection to catch any root crowns that re-sprout.
Herbicides
The most cost-effective control method for heavily infested sites is the use of foliar herbicides. Broadleaf herbicides are preferred over nonselective herbicides to minimize effects on nontarget plants. The rosette should be treated during the growing season.
Spraying the plant when it is in the rosette stage should prevent it from developing seed heads. If rosettes are green into the fall, glyphosate can be applied then when danger to other plants is minimal or non-existent.
Check after a couple of weeks to see if the treatment has been successful. Re-apply if necessary.
Multi-year attention is necessary to control this plant.
Ineffective practices
Mowing and burning by themselves are not successful control strategies. Use them in conjunction with other approaches.
