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Pest Information

Spiny Sowthistle

Spiny Sowthistle

  • Latin Name: Sonchus Asper
  • Common Name: Spiny Sowthistle
  • Other Names: Prickly sowthistle, sowthistle, spiny-leaf sowthistle

Pest Details

Spiny Sowthistle
Spiny Sowthistle
Spiny Sowthistle

Origin:

Native to Europe and Asia, and now widely distributed throughout North America.

Biology:

An annual weed easily confused with Perennial sowthistle and Annual sowthistle. It is separated from Annual sowthistle by the very prickly leaves and presence of a taproot, and from Perennial sowthistle by the prickly leaves as well as the absence of the rhizomes and very large taproot of Perennial.

Identification:

Mature plants can reach 5 feet in height, and the plant grows generally as an upright plant, generally with several unbranched or slightly branched stems arising from the base. Stems are hollow and very large, and all plant parts will exude a milky sap when they are cut or crushed. The leaves are alternate and are most noticeable near the base, where they are up to 6 inches long and with strongly wavy or lobed margins, and with spiny prickles along the margins. Leaves are clasping around the upper stem but on short stalks along the lower stem. Leaves occur on the upper stem primarily at the junction of the stem branches. Flower heads occur on long stalks, either singly or in clusters at the ends of the stems. Flower heads are open and showy, with bright yellow ray and disc flowers. As the flowers dry and the seeds mature the enclosed bracts become widely vase-shaped, with a wide basal area tapering to a narrow tip. Seeds are equipped with a long, white pappus that aids in wind dispersal.

Characteristicts Important to Control:

Heavy seed production and wind dispersal of the seeds will spread the infestation of this plant quickly. Hand removal of individual weeds is effective in landscape, although the strong taproot may make it somewhat difficult.

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