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.
The distribution of Milk Thistle is limited to Europe from Holland southwards. It is unknown in early deposits. It is, moreover, not a native of Britain, and in Scotland and Ireland is quite rare.
The Milk Thistle is really only an introduction. It is found on waste ground, or in gardens where it has been sown with garden seed, or dispersed in the same way as weeds, such as Mallow, Tansy, Wormwood, Chicory, Borage, Mullein, and other casuals.
The stems are thick at the base, branched, rather tall, with cottony down, ribbed, furrowed, and leafless above. The radical leaves are spreading and prostrate, tripinnate, sinuate, shining, with spinose margin, and with white, net-like veins, the stem-leaves clasping the stem.
The flowerheads, which are large and solitary, are purple and globose. The phyllaries are leaf-like below, closely associated, then spreading and bent back, spinous at the margin, leathery, broad, and with one long ter-minal spine. The receptacle is fleshy and hairy. The fruit is oblong, transversely wrinkled, black, with white pappus, growing obliquely. The seeds contain oil for emulsion and are used as bird-seed.
The plant grows to a height of 5 ft. The flowers open in July. Like Cotton Thistle it is a herbaceous triennial, and may be reproduced by seed. It is worth cultivating.
The flowers contain honey, and the tube is long and slender but enlarged above. The flower-head is like Carduus, rather large, rose-colour, with anther-stalks united into a sheath. Being of casual occurrence, observations on the number of visitors are wanting.
The achenes are large and provided with a pappus, which enables them to be dispersed by aid of the wind.
Milk Thistle is more or less a sand-loving plant or addicted to a sand soil or sand loam.
Silybum, Dioscorides, is the Greek name for an edible thistle; marianus, Linnaeus, is from the Virgin Mary, and refers to a legend that drops of her milk fell on the leaves and caused the spotting. Milk Thistle is a common name for it, in allusion to the markings (white veins or spots) of the leaves and the milky juice. From its numerous sharp prickles it was recommended for "stitch" or pain in the side. The achenes are large and contain oil, formerly used for emulsion, and have also been used as food for goldfinches and other birds.
Photo. A. R. Horwood
Mllk Thistle (Silybum Marianum)
The plant was formerly cultivated, the young leaves being used as a salad in spring, or boiled. The young stalks were peeled, and soaked in water to make them less bitter. The second spring the root is eaten like salsify, and the receptacle is pulpy, tasting (and being-eaten) like artichokes.
Essential Specific Characters:173. Silybum marianum, Gaertn. - Stem stout, rigid, branched, leaves oblong, wavy, amplexicaul, with white veins, sessile, glabrous, flowerheads purple, involucral spines recurved, appressed below.