Milk thistle, Silybum marianum (syn. Carduus marianus), is also known as blessed thistle, blessed milk thistle, gundagai thistle, holy thistle, lady’s thistle, Marian thistle, Mary thistle, St Mary’s thistle, Mediterranean milk thistle and variegated thistle. It shares the names blessed thistle and holy thistle with St Benedict’s thistle.
The name milk thistle comes from the white pattern on the leaves (inset), said to be caused by the Virgin Mary’s milk having been spilt on them in the mythic past. It does make them easy to recognize, though.
A native of Southern Europe, North Africa and Western Asia, milk thistle has been introduced successfully into many other parts of the world, so much so that it is considered an invasive weed in North America, Australia, and New Zealand. For this reason, it’s best to check local laws before starting to grow it.
Milk thistle is quite a large plant which can reach a height of 4 feet (120cm) and a spread of 3 feet + (1m). It is a biennial and will need to be sown every year, but cannot be harvested for use in remedies until the seeds have ripened in August-October of the second year. The seeds are important, medicinally speaking. Milk thistle is not fussy about soil, so long as it is well drained, and will cope with very alkaline soil and exposure to strong winds (not sea winds), but not full shade.
Milk thistle used to be grown as a vegetable; flower buds, leaves (after removal of the thorns), young stems (usually soaked and peeled before use) and roots are all edible by humans*, though they are poisonous to ruminants (eg. cows, sheep, goats and other animals which chew the cud). *If you intend to use milk thistle for food, avoid growing it on rich soil, as it tends to concentrate nitrates in the leaves in these circumstances and it is perfectly happy in poor soil.
According to Wikipedia, an extract is used in Rockstar energy drink.
The seeds are the part usually used medicinally, particularly useful in treating or preventing liver damage, being prescribed for liver regeneration. They have a long history of use to treat disorders of the liver including cirrhosis and hepatitis (jaundice), and are also used for gall bladder diseases, to boost the immune system and to treat poisoning. German research confirmed by an American study shows that a chemical in the seed can protect against liver damage caused by eating Amanita muscaria (the fly agaric).
To treat these conditions, make a standard infusion of seeds using 30g (1 ounce) of seed to 600ml (2.5 US cups, 1 UK pint) of boiling water. Steep for from 15 minutes to 4 hours, then strain off the seeds and discard. The dosage is up to 375ml (1.5 US cups, 12 fl oz) per day, in single mouthfuls.
A standard infusion of leaves, made with similar quantities of leaves and water as given in the recipe for seeds above, is used to treat depression, lack of appetite and indigestion. The dosage is up to 250ml (1 US cup, 8 fl oz) per day, split into 3 doses.
As with all herbs grown for medicinal use, milk thistle should be grown organically to avoid corruption of its active constituents by foreign chemicals. As it will grow happily in poor soil and is not generally subject to attack by pathogenic organisms, this should be easy enough. To find out more about growing organic milk thistle visit the Gardenzone.