Sonchus asper

History of Spread

Sonchus asper (Spiny Sow-Thistle) is a native of Eurasia, and is now widespread in North and South America, South Africa, Australia, and New Zealand (Swedish Natural History Musem 2001). Early occurrences in North America may have been overlooked, due to confusion with the similar, also introduced, S. oleracea (Smooth Sow-Thistle). Sonchus asper had been regarded as a variety of the latter species by some botanists (Torrey 1843). The earliest record which we have found is 'salt marshes' near New York (Torrey 1826). This plant is a widespread agricultural weed, but could also be transported by dry ballast, since S. arvensis (Field Sow-Thistle) was found in ballast piles in New York (Brown 1878). Sonchus asper is now a widespread weed of 'waste places, roadsides, etc.' (Fernald 1950) and cultivated ground, and is found in all 50 U.S. states (Agricultural Research Service 1971; Natural Resources Conservation Service 2001).

In the Chesapeake Bay region, the first record of Sonchus asper which we have is a collection from the 'Potomac Flats' in Washington DC in 1874 (Potomac-Side Naturalists' Club 1876; U.S. National Herbarium collections). This plant now occurs throughout MD (Brown and Brown 1984) and in most VA counties (Harvill et al. 1992). Most available records are terrestrial, but Tatnall (1946) described the habitat as: “fields, waste ground, and sands of the seashore'. Sonchus asper was common, at the upper edge of brackish marshes and strandlines in Shady Side and on strandlines at Rose Haven MD, in October 2000 (Fofonoff, personal observations).

References- Agricultural Research Service 1971; Brown 1878; Brown and Brown 1984; Fernald 1950; Fofonoff, personal observations; Harvill et al. 1992; Potomac-Side Naturalists' Club 1876; Swedish Natural History Musem 2001; Tatnall 1946; Torrey 1826; Torrey 1843; Natural Resources Conservation Service 2001; U.S. National Herbarium collections

Invasion Comments