Family: Asteraceae

Origin, Description & Uses
Sonchus asper (spiny sowthistle) is an annual or short-lived perennial herb native to temperate Eurasia, North Africa, the Sahel region, and Somalia. It is characterized by its glossy, deeply lobed leaves with sharp, spiny margins that clasp the stem, and by its bright yellow, dandelion-like flowers that produce abundant wind-dispersed seeds. The species thrives in disturbed habitats, roadsides, agricultural fields, gardens, and open areas. In some regions, young leaves have been used as a cooked green, and the plant has been utilized in traditional herbal practices. Sonchus asper is currently naturalized on Maui and Hawaiʻi Island and is considered potentially naturalizing on Lānaʻi.

Risks & Threats
Sonchus asper is naturalized in Hawaiʻi and possesses several traits that are cause for concern, including rapid growth, prolific seed production, efficient wind dispersal, and an ability to colonize disturbed sites. These characteristics allow it to spread quickly and compete with native vegetation and desirable crops, particularly in open or recently disturbed environments. Although it is most commonly associated with human-altered habitats, its continued expansion could contribute to the degradation of tropical island ecosystems by displacing native plants and increasing weed management challenges. Because of these risks, low-risk or native alternatives are recommended when available. In areas where S. asper is already widespread, landowners and gardeners should avoid intentionally planting or spreading it and should manage existing populations, especially near natural areas and regions where the species is not yet well established, to help minimize further ecological impacts.

High Risk Traits:

• Broad climate suitability and elevation range
  
• Grows in temperate and tropical climates
  
• Widely naturalized worldwide, including the Hawaiian Islands of Maui and Hawaii
  
• A disturbance-adapted weed that impacts several crops
  
• Categorized as an environmental weed in Australia (but not currently recognized as a serious weed of natural areas in the Hawaiian Islands)
  
• Other Sonchus species are invasive
  
• Prickly leaves
  
• Potentially allelopathic
  
• Host of several economically important plant pests and parasites
  
• Tolerates many soil types
  
• Reproduces by seeds
  
• Self-compatible
  
• An annual, able to reach maturity in one growing season
  
• Seeds dispersed by wind, water, by adhering to animals, vehicles, other machinery, as a produce contaminant, and internally by animals
  
• Capable of prolific seed production
  
• Seeds may persist in the soil for one year in the field, and possibly longer
  
• Difficult to control mechanically due to taproot

Low Risk Traits:

• Typically invades disturbed or degraded habitats rather than intact native ecosystems
  
• Palatable to livestock
  
• Probably shade intolerant; thrives in areas with full sun
  
• Certain herbicides may provide effective control