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Silybum marianum
Also called Milk Thistle, Blessed Milk Thistle, Variegated Thistle, Holy Thistle, St. Mary's Thistle, Bull Thistle, Gundagai Thistle
Silybum marianum is an upright thistle, usually grown as an annual, with shiny green leaves veined in white and red-purple flower heads. The sources describe the species, not a genus; it is grown mainly for its seeds, which yield silymarin.
Silybum marianum is a species of thistle. It has various common names including milk thistle, blessed milkthistle, Marian thistle, Mary thistle, Saint Mary's thistle, Mediterranean milk thistle, variegated thistle and Scotch thistle (not to be confused with Onopordum acanthium or Cirsium vulgare). This species is an annual or biennial plant of the family Asteraceae. This fairly typical thistle has red to purple flowers and shiny pale green leaves with white veins. Once native from Southern Europe through Asia, it has spread throughout the world.
Milk thistle is an adaptive crop with low requirements. It is mainly cultivated as a medicinal plant but it is also sometimes used as a food source. It's mainly cultivated in Europe but also in Asia and North America. Milk thistle is a biennial plant, it is normally grown as an annual plant, which simplifies cultivation. When the main requirements of the plant are met, then the milk thistle will blossom in the first year.
Milk thistle has low soil nutrient requirements and is drought resistant. The optimal pH ranges from 5.5 to 7.6, but a wide range is acceptable. The seeds are directly sown into the soil with a sowing depth of 1 to 1.5 cm. For germination, a minimal temperature of 2 °C (36 °F) is needed. Sowing can be done in Autumn or in Spring, depending on the climate conditions. Row spacing is between 40 and 75 cm with a plant space of about 25 cm in the rows. Fertilization is not necessarily needed because of the low nutrient requirements.
Traditional milk thistle extract is made from the seeds (technically the whole fruit), which contain approximately 4–6% silymarin. The extract consists of about 65–80% silymarin (a flavonolignan complex) and 20–35% fatty acids, including linoleic acid. In the water-soaked fruit, 41% of the mass is of the pericarp and 52% the mass is of the kernel (actual seed). Almost all of the flavolignan content is found in the pericarp.
Silymarin is a complex mixture of polyphenolic molecules, including seven closely related flavonolignans (silybin A, silybin B, isosilybin A, isosilybin B, silychristin, isosilychristin, silydianin) and one flavonoid (taxifolin). Silibinin, a semipurified fraction of silymarin, is primarily a mixture of 2 diastereoisomers, silybin A and silybin B, in a roughly 1:1 ratio. More complete extraction of flavonolignans from the fruit is a topic of ongoing research.
Silybum marianum is native from around the Mediterranean and much of Europe to Central Asia and India; in Africa it reaches as far south as Ethiopia. It is possibly native near the coast of southeast England. S. marianum has been widely introduced outside its natural range, for example into North America, Hawaii, Australia, New Zealand, and Colombia where it is considered an invasive weed. It also spreads invasively in almost all of Europe as a consequence of field cultivation.
Although potentially allergenic, the leaves and stems can be gathered ahead of bloom, the spines removed, and boiled with salt. The roots are edible raw or roasted and the flower head can be cooked like globe artichoke.
Text excerpted from the Wikipedia article Silybum marianum by its contributors, under CC BY-SA 4.0; the excerpts and the care summary drawn from them are shared under the same licence.
The care summary was written by AI (Claude, Anthropic) from the sources on this page, with general growing knowledge where they are silent. Check before relying on it.
Life form, climate and native range: World Checklist of Vascular Plants, Royal Botanic Gardens, Kew (CC BY 3.0), reformatted; see Plants of the World Online.
