Cirsium and Carduus species - Thistles

Cirsium arvense Creeping Thistle has grooved, ±spineless stems which are not cottony. There is no basal rosette, and the stem leaves are grey-green above and cobwebby below. There are many small lilac flowers with a bulbous flower base, egg-shaped bracts, tightly pressed and outer spine tipped bracts spreading outwards.

Cirsium vulgare Spear Thistle has a grooved stem, with interrupted spiny wings and cottony. The basal rosette leaves are ovate and ±not lobed in first year. The upper surface is bullate and more lobed in second year with spear-shaped, lobed leaves ending in a stout spine and petioles are less spiny towards the base. One or two larger flowers in each head and the bracts at flower base are narrow, spreading and spine tipped.

Cirsium palustre Marsh Thistle has cottony stems with continuous spiny wings. The leaves are hairy above, narrowly lobed and spine tipped, often with purple borders. The basal leaves more deeply lobed than C. vulgare and the petioles are armed with spines all the way to the base. Smaller crowded leafy clusters of flowers with bracts pointed, but not spine tipped.

Cirsium heterophyllum Melancholy Thistle has an obliquely ascending, pale green stem usually with few stem leaves and 1 (-3) capitula. 25-30mm across. The stem is not winged or spiny and usually arachnoid hairy (cobweb). Basal leaves are broadly lanceolate, acute at the tip with spinulose-serrate teeth and grey beneath. Stem leaves are thinner and amplexicaul. Phyllaries are lanceolate with a weak, spiny, dark tip.

Carduus nutans Musk Thistle has discontinuously spiney wings along the hairy stem which stop on the petioles below the solitary, large capitula (30-65mm across excluding the flowers). The outer phyllaries are strongly reflexed and the capitula is pendant to 90º

Carduus crispus Welted Thistle has a continuously winged cottony stem nearly up to capitula which is in clusters of 2-4, each 15-20 mm across excluding the flowers. The phyllaries stick out. The stem leaves have broader side lobes than Cirsium palustre or C. vulgare.

Stace, Poland, Crewe, Streeter Nov25