Gardening Magazine

Plant of the Week: Silybum Marianum

By Davis Landscape Architecture @DavisLandArch
Silybum marianum Flower (05/05/2012, Kew, London)

Silybum marianum Flower (05/05/2012, Kew, London)

Position: Full sun

Flowering period: Late Spring to summer

Soil: Moist, well drained

Eventual Height: 2m

Eventual Spread: 1.6m

Hardiness: 5a – 9b

Family: Asteraceae

Silybum marianum is a fast growing biennial plant. Its shiny green leaves are either lobate or pinnate, with spiny edges, with white veins and up to 1m long. The flower stem is grooved, becoming hollow with age. Its bright purple flowers are up to 12 cm across and give rise to spiny, hairless bracts. Its fruit is a black achene, with a simple long white pappus, surrounded by a yellow basal ring. 

Silybum marianum (05/05/2012, Kew, London)

Silybum marianum (05/05/2012, Kew, London)

Silybum marianum, commonly known as Milk Thistle, Blessed Milk Thistle, Marian Thistle, Saint Marys Thistle, Scotch Thistle and Mediterranean Milk Thistle, is native to Southern Europe through to Asia. It is possibly native near the coast of the south east of England. It has been globally introduced outside its natural range. Due to its ability to self seed readily  it is considered an invasive weed in a number of countries. It has a long history as a medicinal plant, and is currently farmed to produce herbal remedies.

The etymological root of the binomial name Silybum is the name applied by Discorides to some edible thistle like plants. Marianum is derived from the story that white marks on the leafs resulted from drops of milk shed by Mary when she nursed Christ.

Silybum marianum Detail (05/05/2012, Kew, London)

Silybum marianum Detail (05/05/2012, Kew, London)

The landscape architect may find Silybum marianum useful as a dramatic biennial accent plant in wildlife gardens. Caution should be exercised in specifying this plant as it readily self seeds when conditions are suitable.

Ecologically, S. marianum is attractive to bees and pollinating insects. Its leaves are a food for a number of caterpillars.

S. marianum prefers moist, fertile, well-drained soils. It tolerates most pH of soil, it will tolerate very alkali soils.

Silybum marianum requires little maintenance. Unwanted self seeded seedlings should be removed whilst young.

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