Rose Thistle

Cirsium andersonii grows in the Cascade Range of northern California south through the Sierra Nevada of eastern California and western Nevada. It has been reported from the mountains of southwestern Idaho, but I have not seen specimens from there.

Heads of Cirsium andersonii are actively visited by hummingbirds as well as a variety of insects (P. L. Barlow-Irick 2002).

Perennials (but often appearing biennial), (15–)40–70(–100) cm; rootstocks producing erect, taprooted caudices and rosettes. Stems usually 1, erect, sub-glabrous to puberulent and/or tomentose; branches 0–several, stiffly ascending. Leaves: blades ± elliptic, 8–35 × 4–8 cm, divided about halfway to midveins, lobes spreading, triangular, coarsely dentate or with a few broad lobes, obtuse to acute, main spines 1–5 mm, abaxial faces green or gray, thinly tomentose, adaxial green and glabrous to sparingly pilose; basal often present at flowering, spiny winged-petiolate; main cauline reduced distally, bases clasping; distal much reduced, linear-oblong, usually less deeply lobed and often spinier than proximal. Heads 1–6, borne singly or in corymbiform, racemiform, or spiciform arrays. Peduncles 0–20 cm. Involucres broadly cylindric to narrowly campanulate, 3–5 × 2–4 cm, loosely arachnoid or ± glabrous, finely short-ciliate. Phyllaries in 6–8 series, imbricate, outer green, inner purple to red, linear-lanceolate (outer) to linear (inner), abaxial faces without glutinous ridge; outer and mid bodies short, appressed, entire or spinulose-ciliate, apices long-spreading to ascending, entire or spinulose-ciliate or rarely with expanded, fringed appendages, spines straight, weak, 1–3 mm; apices of inner red to purple, straight or rarely twisted, long, flat, entire. Corollas red to reddish purple, 30–45 mm, tubes 10–20 mm, throats 10–16 mm, lobes 9–11 mm; style tips 3.5–5 mm. Cypselae brown, 6–7 mm, apical collars narrow; pappi 25–40 mm. 2n = 32, 64.

Cnicus andersonii A. Gray, Proc. Amer. Acad. Arts 10: 44. 1874

Cirsium andersonii is a North American species of thistle known by the common names Anderson's thistle and rose thistle. It is native to California, Oregon, and Nevada, where it grows in the woodlands and forest openings of the local high mountain ranges, including the Sierra Nevada and the southern Cascade Range. It has also been reported from Idaho.

This native thistle is a perennial herb growing erect to a maximum height approaching 100 cm (39 in). It produces one to multiple stems, simple or branching, which may be hairless to quite woolly. The deeply lobed and sharply cut leaves are borne on spiny-winged petioles, the longest toward the base of the plant reaching over 30 centimetres (12 inches) long. The inflorescence bears one or more flower heads, each up to 5 centimeters long by 4 wide at the largest. The head is lined with spiny, purple-tipped phyllaries which curve outward. The head contains many red, purplish, or rose pink flowers, each up to 4.5 centimeters long. The fruit is an achene with a brown body 6 or 7 millimeters long topped with a pappus which may be 4 centimeters in length. The flower heads attract hummingbirds.

It was originally named Cnicus andersonii after Charles Lewis Anderson by Asa Gray; its name was later changed to Cirsium andersonii by Petrak.