Annual Sowthistle Illustration

Annual Sowthistle

Sonchus oleraceus

Annual Sowthistle is a winter annual broadleaf weed that is also referred to as Common Sowthistle, Hare's Lettuce, Colewort or Milk Thistle or by its scientific name, Sonchus oleraceus.

Identify

Rosette

Rosette

Lobed

Lobed

Pinnatifid

Pinnatifid

Annual Sowthistle is an annual broadleaf weed that can be identified by its unbranched growth habit with smooth, vertically growing stems. Its stems and foliage appear succulent and waxy and are whitish or bluish in color. It also has leaf margins that are slightly prickly, but no other spines are present. The lobes at the base of the petiole clasp the stem. The weed has a short taproot, and its leaves, stems, and roots exude a white sap when broken or cut. Blooming from late spring to mid-summer, this broadleaf weed produces small clusters of flower heads that bloom during the morning and close around noon. Each flower head consists of numerous yellow ray florets and no disk florets, similar in appearance to the Dandelion.

Life Cycle

This broadleaf weed prefers to grow in soils that are disturbed by construction and civilization. For this reason, Annual Sowthistle can often be found in fields, gardens, residential lawns, open pastures and along roadsides and the edges of buildings throughout much of North America.

Life Cycle Image

Control

Sonchus oleraceus can grow quite quickly under the right conditions and in a wide range of areas. This weed rarely invades natural areas and is usually found in poorly maintained areas near homes, lawns and gardens. Cultural weed control methods, such as good mowing and watering practices, are typically not effective for complete removal, and professionally applied broadleaf weed killers are often necessary.

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