Perennial Sowthistle

PERENNIAL SOWTHISTLE

(Creeping sow-thistle, field sow-thistle, field milk thistle)

Habitat: Cultivated fields, meadows and roadsides

Description: Perennial Sowthistle is a creeping perennial with an extensive horizontal root system.  It is reproduced by seeds and underground roots.  The roots penetrate to a depth of 1.5 - 3 meters.  The stem, which can grow up to 1.2 meters, is hollow, smooth and branches at the top.  The plant also contains a milky substance inside the stem.  The leaves alternate with a slightly toothed edge.  Lower leaves have deep cut, backward pointing lobes.  Leaves are approximately 15 - 30 cm long with upper leaves being smaller.  The flowers are yellow in color; almost like a dandelion.  They are 1.3 - 5 cm across.  Seeds are small, brown, ridged and crowned with a tuft of fine hairs.

Control Practices: Tillage is the most effective way to control Perennial Sowthistle because it starves the root system.  Start tillage as soon as possible after harvest, preferably with a cultivator.  The next spring on of the following should be completed:

1. Start tillage early in spring and continue until freeze-up.  Green growth should not remain above ground for more than a week.

2. Start tillage when the buds are in their early stage as this is when the plant is the weakest.  Continue tillage until freeze-up.

3. Summerfallow until mid July to control other weeds.  Then leave the Prennial Sowthistle undistrubed.  When it reaches the early bud stage is should be sprayed with the appropiate chemical.

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