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DESCRIPTION:
Russian thistle is a common annual broadleaf weed. It is found in saline areas. It occurs throughout the western states, usually more often in drier areas. The cotyledons (seed leaves) and first true leaves are long and thin, like pine needles. Leaves alternate along the stem, but may appear to oppose one another because of the short length between stem joints. Subsequent leaves are soft, fleshy, with small spines at the tips. Stems are thin, flexible, and often have reddish-purple striations.
Mature plants are spherical bushes up to about 3 feet or more (1 m) tall. Stems are striated purple or green, rigid, and typically curve upward. Leaves are more or less bluish-green, fleshy to leathery, hairless or covered with stiff short hairs. Leaf tips are sharp-pointed to spine-tipped. Flowers are borne in the junctions between the leaves and the stem. Although they lack petals, they have winglike appendages that look like petals. After they turn grayish brown, the plants break away from the roots at the soil line, becoming tumbleweeds that scatter their seeds. Seeds are flattened-round to somewhat conical, gray to brown, have a thin seed coat, and a dark greenish-brown coiled embryo inside. It is a preferred host of the beet leafhopper. The common soil-applied herbicides generally provide good control of this weed, but the seeds germinate deeper than most, so control may be poor where incorporation is shallow.
See UC IPM's Russian Thistle
Pest Note for more information.
Broadleaf ID illustration.
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