This section is from the book "British Wild Flowers - In Their Natural Haunts Vol2-4", by A. R. Horwood. Also available from Amazon: A British Wild Flowers In Their Natural Haunts.
Though usually connected with corn-growing, and so modern, this plant can claim some antiquity, having been found in Lacustrine deposits of Neolithic age. To-day it is found in Arctic Europe, North Africa, Temperate Asia, and India. In North America it is an introduction. In Great Britain it is found in every part of the country except N. Ebudes, as far north as the Shetlands. In Northumberland it is found at 1000 ft. It occurs in Ireland and the Channel Islands.
Common Sow-Thistle is a frequent cornfield plant, growing in numbers amid the ripening grain, and as it is one of those plants that are especially sensitive to light it turns its head to the sun, being heliotropic in this respect, as are the leaves and flowers of many other plants. This plant grows also on waste ground, and is essentially a follower of man and the plough.
The root is milky, spreading, and difficult to dislodge. The stem is tall, simple, with radical leaves divided, with lobes enlarged upwards the lobes turned back, heart-shaped at the base, the leaves being" alternate, clasping, smooth, pale below, dark-green above. The edges are lined with prickles. Some leaves are linear-acute higher up.
The flowers are yellow, borne on flower-stalks which are highly glandular, with black or brown hairs, and in a sort of umbel also like the leaf-like organs, which are unequal, keeled, very hairy, and glandular. The fruit is rough and transversely downy, not beaked. The pappus is stalkless, the hairs numerous.
The plant is 1 1/2 ft. high. Flowers are to be seen in July and August. The plant is perennial.
The flowers are as conspicuous as those of the Dandelion, and built upon much the same plan, attracting many insects, though hidden, or rather appearing just above the corn before it is ripe. The corolla is yellow, like that of most hermaphrodite florets in Compositae. Each floret is tubular, with a white tube, which is narrow and beset with hairs above, to preserve the honey at the base of the stigmas, and the limb is yellow, as long as the tube, with edges rolled from the back inwards.
The stamens unite to form a cylinder, the two threadlike stigmas are bent inwards, and the style is hairy above, with slender lobes. Thus cross-pollination is rendered possible by the sweeping of the pollen out of the tube away from the stigma. The plant is visited by the Honey Bee, Bombus, Panurgus, Halictus, Nomada, Megachile, Osmia, Syrphidae, Eristalis, Cheilosia, Conopidae. Sicus, Lepidoptera, Hesperia, Coleoptera, Curculionidae, Spermophagus cardui, Malacoder-mata, Malachius.
Photo. B. Hanley - Corn Sow-Thistle (Sonchus arvensis. L.)
The many rows of silky pappus or hair assist in the dispersal of the achenes by the wind.
Corn Sow-Thistle is a sand plant, fond of sand soil or sandy loam, growing on the sandy portions of the Triassic and Liassic formations, etc.
The fungi Puccinia sonchi, Coleosporitim sonchi, Aecidium sonchi, Bremia lactucae all attack it.
The three moths, Hecatera serena, July Chi (Polia chi), Shark (Cucullia umbratica), and two flies, Eusina sonchi, Tephritis tessellata, are found on it.
The name Sonchus, of Theophrastus, is from the Greek name of the plant, sonchos, and said to be from the Greek soos, safe, and echein, to have, because it yields a health-giving juice. The second Latin name proclaims its preference for cultivated ground.
The names Dindle, Gutweed, Hogweed, Rosemary, Swine Thistle, Tree Sow Thistle are also given to Corn Sow-Thistle. Gutweed is applied to it because of its long creeping roots, which wind about.
In Russia they say the plant belongs to the Devil. Like the Evil Spirit in northern mythology it is spoken of sometimes as sowing weeds amongst the good seed, from whence has originated, it is said, the popular saying, "Sowing one's wild oats". It was believed to reveal hidden treasure when appealed to, possibly because of its golden flowers and heliotropic property. Rabbits and hares are especially fond of it, hence their occurrence in cornfields. Goats, sheep, and pigs eat it.
The young tender leaves are eaten as greens and as spinach.
Essential Specific Characters: 184. Sonchus arvensis, L. - Stem tall, simple, leaves runcinate, toothed, upper entire, long, flowerheads large, yellow, in corymb, peduncles and involucres glandular, hairy.