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A Beautiful Plant Called Milk Thistle!

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By: Aysel Akdeniz

I have been hiking regularly with friends over the weekends. During our hikes we come across many different plants and animals that made me always wonder about the story behind them.

On a recent hike over the weekend we went to a local county park and saw this very captivating purple color flower on a green plant.

Silybum marianum has other common names including Cardus marianus, milk thistle, blessed milk thistle, Marian thistle, Mary thistle, Saint Mary's thistle, Mediterranean milk thistle, variegated thistle, and Scotch thistle (though not to be confused with Onopordum acanthium). This species is an annual or biennial plant of the family Asteraceae. This typical thistle has red to purple flowers and shiny pale green leaves with white veins. Originally a native of Southern Europe through to Asia, it is now found throughout the world.

Milk thistle is an upright herb which can grow to be 30 to 200 cm (12 to 79 in) tall and have an overall conical shape. The approximate maximum base diameter is 160 cm (63 in). The stem is grooved and may be covered in a light cottony fuzz. The largest specimens have hollow stems.

The leaves are oblong to lanceolate and 15–60 cm long and typically pinnately lobed, with spiny edges like most thistles. They are hairless, shiny green, with milk-white veins.

The flower heads are 4 to 12 cm long and wide, of red-purple color. They flower from June to August in the North or December to February in the Southern Hemisphere (summer through autumn). The flower head is surround by bracts which are hairless, with triangular, spine-edged appendages, tipped with a stout yellow spine. The fruits are black achenes with a simple long white pappus, surrounded by a yellow basal ring. A long pappus acts as a “parachute”, supporting seed dispersal by wind.

Distribution and Habitat

S. marianum is native to the Mediterranean region of Europe including Greece (mostly in Crete), east into Iran and Afghanistan. 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, Colombia where it is considered an invasive weed.


  1. BSBI List 2007 (xls). Botanical Society of Britain and Ireland. Archived from the original (xls) on 2015-06-26. Retrieved 2014-10-17.

  2. “Silphium marianum”. Natural Resources Conservation Service Plants Database. USDA. Retrieved 15 November2015.

  3. Flora of North America Editorial Committee (ed.). “Silybum marianum”. Flora of North America North of Mexico (FNA). New York and Oxford-via, Missouri Botanical Garden, St. Louis, MO & Harvard University Herbaria, Cambridge, MA.

  4. Flora of Australia Volume 37: Asteraceae. Melbourne: CSIRO Publishing. 2015 ISBN 9781486304158. Retrieved 9 August 2020.

  5. Rose, Francis (1981). The Wildflower Key. Frederick Warne.pp.388-9. ISBN 978-0-7232-2419-8.

  6. “Milk Thistle”. Fraser Valley Invasive Species Society. Retrieved 24 January 2021.

  7. Jahn, Ralf; Schoenfelder, Peter (1995). Exkursionsflora fur Kreta.E. Ulmer. ISBN 978-3800134786.

  8. Bernal; Gradstein; Celis (2019). Catalogo de plantas y liquenes de Colombia. Bogota: Instituto de Ciencias Naturales, Universidad Nacional de Colombia.

  9. “Silybum marianum”. Plantpono. Retrieved 9 August 2020.

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