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Cirsium vulgare (spear thistle) is listed in the United States (where as a non-native invasive species it has been renamed "bull thistle") as a noxious weed in nine states. [6] Some species in particular are cultivated in gardens and wildflower plantings for their aesthetic value and/or to support pollinators such as bees and butterflies.
Cirsium silvaticum Tausch Cirsium vulgare , the spear thistle , bull thistle , or common thistle , is a species of the Asteraceae genus Cirsium , native throughout most of Europe (north to 66°N, locally 68°N), Western Asia (east to the Yenisei Valley), and northwestern Africa ( Atlas Mountains ).
Typically, an involucre with a clasping shape similar to a cup or urn subtends each of a thistle's flower heads. The typically feathery pappus of a ripe thistle flower is known as thistle-down. [1] The spininess varies considerably by species. For example, Cirsium heterophyllum has very soft spines while Cirsium spinosissimum is the opposite. [2]
The flowers are usually dioecious, but not invariably so, with some plants bearing hermaphrodite flowers. [20] The seeds are 4–5 mm long, with a feathery pappus which assists in wind dispersal. [ 26 ] [ 27 ] [ 28 ] One to 5 flower heads occur per branch, with plants in very favourable conditions producing up to 100 heads per shoot. [ 14 ]
Cirsium erisithales can reach a height of 50–150 millimetres (2.0–5.9 in). The stems are erect, almost hairless. This plant has just a few leaves, with tooth-shaped lobes. Flower heads are lemon yellow, solitary or in groups (up to 5), with a diameter of 25–30 millimetres (0.98–1.18 in). [4]
Cirsium horridulum, called bristly thistle, purple thistle, or yellow thistle is a North American species of plants in the tribe Cardueae within the family Asteraceae. It is an annual or biennial . [ 2 ]
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This thistle's occurrence is linked to the spread of human agriculture from the mid-Holocene era or before. [9] It is a constant plant of several fen-meadow plant associations, including the Juncus subnodulosus-Cirsium palustre fen-meadow. [9] The flowers are visited by a wide variety of insects, featuring a generalised pollination syndrome. [10]