Russian Thistle

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Biology

Russian thistle is an annual weed, reproducing by seeds. The stems are up to 1.2 m tall, red striped, and spread as much or more horizontally as vertically. The leaves are alternate, long, 2-5 cm, narrow, dark green, and fleshy. The later leaves are shorter, broader, and are tipped with stiff spines. The flowers are small, 2 mm wide, green or pinkish, inconspicuous, and occur in the axils of upper leaves. Two spiny-tipped bracts accompany each flower. The seeds are a cone shaped coiled utricle, 2 mm in diameter, dull brown to grey in colour.

Russian thistle can produce up to 200,000 seeds per plant. When mature it acts as a tumbleweed, rolling along with the wind spreading seeds as it travels. This weed is a high user of nitrogen and this can indirectly affect the growth of desirable plant species.

Scouting Techniques

Take a minimum of 20 weed counts across the field.

Effects On Crop Quality

Nitrates and soluble oxalates accumulate in the plants photosynthetic parts at levels poisonous to sheep.

Control Tips

• Group 22 herbicide application in non-crop areas
• mowing
• cultivation
• Groups 9 &10 in herbicide tolerant crops