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Milk Thistle

Silybum marianum

Plant Description

A broadleaved herbaceous annual or biennial thistle with distinctive green and white marbling on spiny-margined leaves. Solitary large purple flower surrounded by 1 to 2-inch spines.

Plant Details

Life Forms
ODA Listing
Soil and Moisture Conditions
Suggested Actions
Shade Preference
Mature Height 2 -6'
Distribution Found in the Americas, Europe, Australia, New Zealand and its native range.widespread in southwestern Oregon and Willamette Valley.
Control Keep milk thistle from establishing by planting competing vegetation. Hand pull small patches (carefully) and replant with native plants. Cut plant about one inch below soil surface to keep plants from resprouting. Clean equipment to keep from spreading this plant to new sites.
Reproduction and Spread Spreads by seed- one plant can produce 6000 seeds that remain viable for up to 9 years. Seeds are spread by wind, water, mud, equipment and vehicles and in seed packets.
Introduced Native to Middle East, India, North Africa and parts of Europe.
Look Alikes Other thistles including Italian, Canada and Bull Thistles.
Impact Harmful to livestock due to its spines and nitrate poisoning.
More Info
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