Common Name: Milk Thistle

General Information

Silybum marianum is an annual to biennial plant producing a rosette of leaves in its first year of growth followed by a branched flowering stem that can be 50 - 200cm tall[, ].
The plant has a wide range of traditional uses as a food and a medicine - it is often harvested from the wild and has a history of cultivation as a minor crop for food, oil and, more commonly, as a medicine. Modern research has shown that the plant is a very effective medicine, especially in the treatment of liver conditions and poisoning. The plant is also sometimes grown as an ornamental.
Silybum marianum has been spread by human activity, especially through cultivation as a medicinal plant. It has become a seriously invasive weed in Australia, parts of the USA and South America, South Africa and in New Zealand. It invades pastures where, once established, it can eliminate most other plant species. It can also hinder movement of livestock and people. It is a weed of cultivated land as well as being a nuisance along roadsides and in waste areas. In addition to problems and injuries caused by its spiny thistles, it can, under certain conditions, accumulate nitrogen and become seriously toxic to livestock[].

Known Hazards

Under certain circumstances the plant can concentrate considerable amounts of nitrate in its foliage. This tends to be most serious when heavy rainfall follows a prolonged drought; when heavy dressings of fertiliser are applied to crops; or after plants have been treated with herbicide. The nitrate is microbially reduced to nitrite in the gut - this then reacts with haemoglobin in the blood, leading to a condition known as methaemoglobinaemia, which causes affected animals to stagger, vomit and have laboured breathing, resulting in death if not treated[].

Botanical References

, ,

Range

Macaronesia (Madeira), throughout the Mediterranean region and eastwards through Asia to southeastern Siberia, Afghanistan and northern India

Habitat

Roadsides, pastures and waste places, often close to the sea, especially if the ground is dry and rocky[, , , ].

Properties

Weed Potential	Yes
Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Biennial
Height	1.20 m
Growth Rate	Fast
Pollinators	Bees
Cultivation Status	Wild

Cultivation Details

Silybum marianum is a moderately cold-hardy plant, able to tolerate temperatures down to around -15°c when fully dormant[].
Succeeds in any well-drained fertile garden soil[, ]. Grows best if the soil is rich in itrogen[]. Prefers a calcareous soil[] and a sunny position[].
The blessed thistle is a very ornamental plant that was formerly cultivated as a vegetable crop[, , ].
Seed extracts are produced commercially in Europe[].
Young plants are prone to damage from snails and slugs[].
Plants will often self sow freely[].

Edible Uses

Root - raw or cooked[, , , , ]. A mild flavour and somewhat mucilaginous texture[]. When boiled, the roots resemble salsify (Tragopogon hispanicus)[, , ].

Leaves - raw or cooked[, , , , , ]. The very sharp leaf-spines must be removed first[, ], which is quite a fiddly operation[]. The leaves are quite thick and have a mild flavour when young, at this time they are quite an acceptable ingredient of mixed salads, though they can become bitter in hot dry weather[]. When cooked they make an acceptable spinach substitute[]. It is possible to have leaves available all year round from successional sowings[].

Flower buds - cooked[, ]. A globe artichoke substitute[, ], they are used before the flowers open. The flavour is mild and acceptable, but the buds are quite small and even more fiddly to use than globe artichokes[].

Stems - raw or cooked[, ]. They are best peeled and can be soaked to reduce the bitterness[, ]. Palatable and nutritious[, ], they can be used like asparagus or rhubarb[] or added to salads. They are best used in spring when they are young[].

A good quality oil is obtained from the seeds[].

The roasted seed is a coffee substitute[, , , ].

Medicinal

Blessed thistle has a long history of use in the West as a remedy for depression and liver problems[]. Recent research has confirmed that it has a remarkable ability to protect the liver from damage resulting from alcoholic and other types of poisoning[].

The whole plant is astringent, bitter, cholagogue, diaphoretic, diuretic, emetic, emmenagogue, hepatic, stimulant, stomachic and tonic[, , , , ]. It is used internally in the treatment of liver and gall bladder diseases, jaundice, cirrhosis, hepatitis and poisoning[].
The plant is harvested when in flower and dried for later use[].

Silymarin, an extract from the seed, acts on the membranes of the liver cells preventing the entry of virus toxins and other toxic compounds and thus preventing damage to the cells[]. It also dramatically improves liver regeneration in hepatitis, cirrhosis, mushroom poisoning and other diseases of the liver[, , ].
German research suggests that silybin (a flavonoid component of the seed) is clinically useful in the treatment of severe poisoning by Amanita mushrooms[].
Flavonoids in the seeds are now known to be effective as antidotes to severe liver breakdown resulting from ingesting Amanita spp. (Death Cap mushroom), being able to displace phalloidin from membrane receptors[].
Regeneration of the liver is particularly important in the treatment of cancer since this disease is always characterized by a severely compromised and often partially destroyed liver[].

A homeopathic remedy is obtained from equal parts of the root and the seed with its hulls still attached[]. It is used in the treatment of liver and abdominal disorders[].

Agroforestry Uses:

The flowers provide a valuable source of nectar for bees[].
The plant has been trialled as a potential biomass crop in Sardinia[].
A good green manure plant, producing a lot of bulk for incorporation into the soil[].

Other Uses

An oil is obtained from the seed[].

Propagation

Seed - if sown in situ during early spring or mid spring, the plant will usually flower in the summer and complete its life cycle in one growing season[]. The seed can also be sown from May to August when the plant will normally wait until the following year to flower and thus behave as a biennial[]. The best edible roots should be produced from a May/early summer sowing, whilst sowing the seed in the spring as well as the summer should ensure a supply of edible leaves all year round[].