Coastal Invasive Species Committee

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Milk Thistle

Silybum marianum

 

ERADICATE

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      Family: Asteraceae

Other Common Names: Blessed milkthistle, spotted thistle, variegated thistle

Origin: Mediterranean region.

Growth Form/Reproduction: Biennial to short-lived perennial; seeds.

Legal Status: None.

Impacts:
Agricultural: Infests pastures and rangelands. Can cause nitrate poisoning in sheep and cattle
Ecological: Aggressive plant can replace native vegetation and reduce wildlife habitat.
Human: Ornamental and medicinal plant.

Habitat: Full sun to part shade; does best in disturbed soils. Moist to dry roadsides, ditches and disturbed waste places.

Status and Distribution: Rare in Nanaimo, Capital and Cowichan Valley Regional Districts. Not present elsewhere in the Coastal ISC area.

Management Strategy: Eradicate small populations before seed bank is established; seeds remain viable for up to 9 years so monitoring is required on treated sites. On small sites, plants can be pulled or excavated by hand, before seeds develop. Dense stands can be cleared with brush cutters, or loppers. Triclopyr, 2,4-D, aminopyralid, and glyphosate are effective herbicides. No biocontrols are available.

 

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