Flodman’s thistle

not listed

N5? - Secure

SNR - Unranked

not listed

FAC - Facultative

FAC - Facultative

FACU - Facultative upland

Flodman’s thistle is an erect, perennial forb. It can be 12″ to 55″ tall but usually reaches no more than 32″ in height. New plants rise usually on a single stem from short-lived, horizontal, creeping roots and eventually develop a taproot.

The stems are erect and slender, unbranched or with just a a few ascending branches above the middle. They are not winged and do not have spines. They are densely covered with short, white, matted or tangled, soft, woolly hairs (tomentose). As the plant ages the stem remains tomentose.

This plant first appears as a rosette of basal leaves. The basal leaves are inversely lance-shaped to narrowly elliptic in outline, up to 16″ long, and up to 4″ wide. They taper at the base to a winged leaf stalk. They are deeply lobed (pinnatifid), sometimes cut to the midrib. The lobes are triangular lance-shaped, sharply pointed, and seldom more than ¼″ wide. The upper surface of the leaf blade is light green or grayish-green and thinly tomentose at first, becoming hairless or nearly hairless with age. The lower surface is densely white tomentose, and remains so as it ages. The margins are coarsely toothed, spiny, and often rolled under. The first (outer) basal leaves may be unlobed but with spiny margins. The inner leaves become increasingly lobed. Basal leaves are usually absent at flowering time.

Stem leaves are similar, alternate, 1½″ to 16″ long, and ⅜″ to 4″ wide. Lower stem leaves are deeply pinnately divided into long triangular lobes are on winged leaf stalks. The leaves become smaller and shorter stalked but no less divided as they ascend the stem. Upper leaves are well developed and stalkless.

The inflorescence is a single flower head at the end of the stem and each branch tip. Sometimes a cluster of a few heads will rise from an upper leaf axil. The flower heads are stalkless or on up to 2″ long stalks which elevate them above the uppermost leaves. They are not subtended by a ring of spiny, leaf-like bracts.

The whorl of bracts at the base of the flower head (involucre) is egg-shaped to broadly bell-shaped, ¾″ to 1⅜″ long, 1″ to 1⅜″ wide, thinly covered with a few cobwebby hairs. They are rounded but not indented at the base. The bracts of the involucre have a 1 ⁄16″ to ⅛″ long, straw-colored spine at the tip, and a dark central zone and a light-colored, sticky ridge. The pale ridge is often called a racing stripe and is an identifying character of many thistles.

The flower heads are about 1″ wide with numerous purple, tubular, disk flowers.

The fruit is a light brown, ⅛″ to 3 ⁄16″ long achene (cypsela). The cypsela has a conspicuous yellow collar near the tip and a tuft of white hairs at the tip.

12″ to 32″

Purple

Field thistle (Cirsium discolor) is a much taller plant, 36″ to 84″ in height. The stems become hairless or almost hairless with age. The upper leaf surface may be hairy but is never tomentose. The flower head is subtended by a ring of spiny, leaf-like bracts. The flower head is larger, 1½″ to 2″ wide. The collar on the cypsela is straw colored.

The Native Thistle Test

Thistles native to Minnesota do not have spiny stems. Grasp the stem near the base of any native thistle loosely in your fist, then slide your fist upwards to just below the inflorescence. If the plant is a native thistle, you will not get a single prickle – it will be “ouchless”. If the thistle is thought to be an exotic (non-native) species, this test is not recommended. Tall thistle is native.

Moderately moist. Meadows, pastures, fields, and railroads. Full sun.

June to September

Sources

2, 3, 4, 5, 7, 24, 28.

Native

Common

Cardueae is a synonym of the tribe name. Cynareae was published first and has precedence. Nevertheless, most sources use the name Cardueae for the tribe.

Plant

Inflorescence

Flower Head

Basal Leaves

Stem Leaves

Stem

Location: Cass County