Weed List

Tall Thistle
[Cirsium altissimum (L.) Spreng]


Thistle of ND
Tall thistle is closely related to field thistle and can be difficult to distinguish. Tall thistle is found in Nebraska where field thistle does not occur, and only field thistle, not tall thistle, is found in Canada. Although both species have been found in North Dakota, they are considered uncommon and the characteristics that are used to distinguish these two species blur in the northern Great Plains.

Tall thistle is a biennial that grows from 3 to 8 feet tall. The stems are light green and freely branched. Most leaves are lanceolate or long-ovate, tapered at the end and not as deeply lobed as field thistle leaves. The leaves are green on top, densely pubescent and white beneath, and 4 to 11 inches long and 1.5 to 4 inches wide. Leaves near the base are largest and gradually are smaller and more elliptical toward the top. The leaves are alternate and toothed or with weak spines. Rosette leaves are similar to the lower leaves of the bolted plant, large and only slightly lobed.

The leaves of tall thistle more closely resemble dandelion leaves, compared to the oak-leaf shape of field thistle.
The heads are 1.5 to 2 inches long and 2 inches wide, mostly solitary at the end of branches. The leaves surrounding the heads are oblong and not divided as they are in field thistle and have shorter spines. The flowers generally are light purple but can be dark purple, rarely white, and flowering occurs beginning in July to early September.

The achenes are pale to dark brown with a yellow apical ring with incomplete stripes, 0.15 to 0.25 inches long and 0.1 inch wide. Wild turkeys often feed on tall thistle seed in the fall.

Tall thistle is commonly found near woods, in open lowlands, and near ditches and roads. It occasionally occurs on the slopes of open prairies. Tall thistle has only been reported in eastern North Dakota.