Invasive Species Council of Manitoba

Perennial Sow Thistle

Sonchus arvensis

Native to western Asia and Europe Perennial Sow Thistle was introduced as a seed contamiant. It is adapted to a wide range of conditions including the ability to grow in saline soils. It is also capable of invading native and disturbed sites such as pastures, cultivated fields, roadsides, gardens and woodlands. Sow Thistle does pest in most soils where there is full sunlight and can become a serious problem in riparian areas. Decaying plants secretes chemicals that prevent the seeds of other plants from germinating.

Branching stems have a leafy base and can grow 2 m tall. Stems also produce a milky sap when cut. Leaves are alternate and have prickled edges. Small yellow flowers that are dandelion-like in appearance are grouped in loose clusters, there can be 20 flowers per plant but they all don't bloom at the same time.

This plant is able to reproduce with wind born seeds and by rhizomes; a small root fragment can form a new plant. New infestations must be controlled before an extensive root system develops.

Information provided byÂ Alberta Invasive Plant Council

Resources

2011 Rural Municipality Distribution Map

2010 Rural Municipality Distribution Map

Sow Thistle MWSA 2009 Survey Map

Alberta Invasive Plant Council Fact Sheet

Back to Terrestrial Invasive Species List

Invasive Species Council of Manitoba

Perennial Sow Thistle

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