The Black Knapweed or Hardhead (Centaurea nigra) is a very common flower of meadows and pastures, flowering from June to September. Its stem is erect, tough, branched, from a few inches to three feet in height. The leaves are long and narrow; the upper ones entire or nearly so, and clasping the stem; and the lower coarsely toothed or divided into lobes. The flower-head has somewhat the appearance of a purple thistle, but the involucre is not prickly. The latter consists of an almost globular mass of closely-overlapping bracts, the visible portions of which are dark brown or black fringes. The florets are generally all equal, but the outer ones are sometimes larger than the others, and sterile.
The Meadow Thistle.
The Great Knapweed (Centaurea Scabiosa) is a somewhat similar plant, but usually larger, its stout, branched stem being generally two or three feet high. It may be easily distinguished by its larger flower-heads, the outer, neuter florets of which are considerably enlarged. As a rule the florets are all purple, but occasionally all are white, or the outer ones white and the others purple. The bracts of the involucre are broad, with a green centre and a dark, downy margin. The fruit is surmounted by a pappus of stiff, bristly hairs of about its own length. This plant is common in the south of Britain, and flowers during July and August.
Two species of Fleabane have to be noticed. They belong to the genus Inula, and are distinguished by a distinct division of the flower-head into disc and ray, and also by two minute 'tails' at the bottom of the anthers.
One of these is the Common Fleabane (I. dysenterica)—a woolly plant, abundant in the moist pastures of the southern counties, flowering from July to September. Its erect stem is loosely branched, from six inches to two feet high. The leaves are oblong and wavy—the lower ones stalked, and the upper clasping the stem with rounded lobes at the base. The flower-heads are yellow, about three-quarters of an inch in diameter, arranged singly on the tips of the branches, or on stalks arising from the axils of the upper leaves. The florets of the ray are spreading, and much longer than those of the disc; and the fruits have a minute cup at the top, from the inside of which spring the hairs of the pappus. The smoke arising from the burning Fleabanes was supposed to kill fleas and other vermin; and the specific name dysenterica is due to the fact that this species has been used as a medicine in cases of dysentery.
The Black Knapweed.
The Great Knapweed.