This section is from the book "Wayside And Woodland Blossoms", by Edward Step. Also available from Amazon: Wayside And Woodland Blossoms: A Guide To British Wild-Flowers.
An upland cornfield in June with Charlock between the short corn-plants is a beautiful sight for the rambler, but the farmer may be pardoned if he fails to take the aesthetic view; for all that vegetable gold must be laboriously hand-picked, or "cleaned," as he would probably express it. Charlock is a weed that keeps close to the farmer; that likes the comparatively light and dry soil of the ploughed field.
It is a hairy annual belonging to the cabbage tribe, which is a branch of the Cruciferae or Cross-worts, so-called from the four petals being arranged cross-wise. In this and the two following species the petals are bright yellow. To make the flower symmetrical there should be four or eight stamens; there are six, and it has been suggested that there were eight, but two have been suppressed. The fruit is an angular pod, with a straight beak, not persistent, and two hairy valves, but containing only one row of dark-brown seeds. Flowers from May to August.
There are many species of Brassica, two of which may be confounded with B. sinapisj they are:
I. Black Mustard (B. nigrum). Stem bristly, upper leaves very narrow, lance-shaped, smooth, with entire or toothed margins. Pods awl-shaped, quadrangular. Beak short and slender, containing no seeds. Valves keeled. Seeds reddish-brown, oblong. Flowers June to September in hedges and wastes.
II. White Mustard (B. alba). Hairy, like B. sinapis, but the hairs pointing downwards. The upper leaves deeply lobed, lyre-shaped, the lobes being again cut and lobed. Stem marked with longitudinal incised lines. Pod short, no longer than the flat thin, or sword-shaped, ribbed beak. Seeds larger than the last, more globose, yellow. Flowers June and July in cultivated ground.
The genus bears the Latin name for the Cabbage, the wild form of which is B. oleracea, a wild plant on the sea-cliffs of South-west England and Wales, from which have arisen the cultivated varieties known as Scotch-kail, cow-cabbage, savoys, brussels sprouts, red cabbage, white cabbage, cauliflower and broccoli.