Milk thistle

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iMilk Thistle

Silybum marianum

Scientific classification

Kingdom:	Plantae
Division:	Magnoliophyta
Class:	Magnoliopsida
Order:	Asterales
Family:	Asteraceae
Subfamily:	Lactucoideae
Tribe:	Cardueae
Genus:	Silybum Adans.

Species

Silybum eburneum
Silybum marianum
Silybum × gonzaloi

This is an article about the true milk thistles. For another plant that is sometimes referred to as a milk thistle, see sow thistle.

Milk thistles are thistles of the genus Silybum Adans., flowering plants of the daisy family (Asteraceae). They are native to the Mediterranean regions of Europe, North Africa and the Middle East.

Thistle Flower

Members of this genus grow as annual or biennial plants. The erect stem is tall, branched and furrowed but not spiny. The large, alternate leaves are waxy-lobed, toothed and thorny, as in other genera of thistle. The lower leaves are cauline (= attached to the stem without petiole). The upper leaves have a clasping base. They have large, disc-shaped pink-to-purple, rarely white, solitary flower heads at the end of the stem. The flowers consist of tubular florets. The phyllaries under the flowers occur in many rows, with the outer row with spine-tipped lobes and apical spines. The fruit is a black achene with a white pappus.

Only two species are currently classified in this genus:

Silybum eburneum Coss. & Dur., known as the Silver Milk Thistle, Elephant Thistle, or Ivory Thistle
- Silybum eburneum Coss. & Dur. var. hispanicum
Silybum marianum (L.) Gaertner, the Blessed Milk Thistle, which has a large number of other common names, such as Variegated Thistle.

The two species hybridise naturally, the hybrid being known as Silybum × gonzaloi Cantó , Sánchez Mata & Rivas Mart. (S. eburneum var. hispanicum x S. marianum)

A number of other plants have been classified in this genus in the past but have since been relocated elsewhere in the light of additional research.

S. marianum is by far the more widely known species. It is believed to give some remedy for liver diseases(e.g. viral hepatitis) and an extract, silymarin, is used in medicine. The adverse effect of the medicinal use of milk thistle is loose stools.