Spiny sowthistle (Sonchus asper)

Synonyms: Sonchus asper ssp. asper, Sonchus asper ssp. glaucescens, Sonchus nymanii

Common Names: Perennial sowthistle, prickly sowthistle

Description: First observed in Michigan by the First Survey in 1838 in Lenawee County.

Habit: Annual or occasionally biennial herb that can reach a height of 2-4 feet.

Leaves: Upper leaves grow up to 6 inches long, have a rounded, widely lobed base and semi-clasping the stem. Lower leaves reach 10 inches long and 3.5 inches wide, spatula-shaped, deep lobes. Coarsely toothed, soft spines; upper surface is waxy and shiny.

Stems: Lined or grooved, green or reddish in color, usually hairless, stout, hollow, crisp but brittle, exude milky sap when broken.

Flowers: Small, loose, open clusters; dandelion-like, 1 inch wide, borne from leaf axils. Flower head is thick, barrel to vase shaped with tiny glandular hairs on the stalk just below flower clusters. Bracts are 3-4 layers sometimes with sparse glandular hairs.

Fruit and seeds: Finely fuzzy with bracts fully open. Brown in color, flattened, oval, 3-4 ribs per side, tuft of white hairs.

Habitat: Native to Europe, Africa and Asia. Can be found in roadsides, waste areas, fields, stream banks and gardens.

Reproduction: By seed. Capable of producing more than 20,000 seeds.

Monitoring and rapid response: Small infestations can be hand pulled while plants are young, prior to seed set, making sure to remove all of the taproot. Can be effectively controlled using any of several readily available general use herbicides such as 2,4-D, glyphosate and more.

Credits: The information provided in this factsheet was gathered from CABI: Invasive Species Compendium and Minnesota Wildflowers.

Individual species images that appear with a number in a black box are courtesy of the Bugwood.org network (http://www.invasive.org).Individual photo author credits may not be included due to the small display size of the images and subsequent difficulty of reading the provided text. All other images appear courtesy of Google (http://images.google.com).

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