Family: Asteraceae

Origin, Description & Uses
Sonchus arvensis (field sowthistle) is a perennial herb native to temperate regions of Eurasia and belongs to the sunflower family (Asteraceae). It produces upright stems, deeply lobed leaves, and bright yellow dandelion-like flowers that develop into wind-dispersed seeds. The species has been used as a leafy vegetable and forage plant in some regions, and young leaves are sometimes harvested for human consumption. It is also valued by some gardeners and beekeepers for its nectar and pollen resources that attract pollinators.

Risks & Threats
Although Sonchus arvensis is not currently known to be naturalized in the Hawaiian Islands, it possesses several traits that are cause for concern. This species reproduces both by abundant wind-dispersed seeds and by creeping underground roots, allowing it to spread rapidly and form dense colonies. In areas where it has become established outside its native range, it can invade agricultural lands, disturbed habitats, roadsides, and natural areas, competing with desirable vegetation and reducing biodiversity. Its ability to regenerate from root fragments makes it difficult to control once established. Because of these characteristics, S. arvensis has the potential to detrimentally impact tropical island ecosystems if introduced and allowed to spread. Plant Pono recommends choosing a low-risk or native alternative whenever suitable options are available.

High Risk Traits:

• A temperate herb capable of growing in regions with tropical climates (e.g. Fiji)
  
• Widely introduced and naturalized, but no evidence in the Hawaiian Island to date
  
• A disturbance-adapted weed that impacts several crops
  
• An environmental weed, impacting desert tortoise habitat
  
• Other Sonchus species are invasive
  
• May contain toxic levels of nitrates
  
• Host of several economically important plant pests and parasites
  
• Shade tolerant
  
• Tolerates many soil types
  
• Forms dense patches that can exclude other vegetation
  
• Reproduces by seeds and vegetatively by subterranean roots
  
• 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 up to 3 years
  
• Resistant to several herbicides
  
• Mechanical control measures may be ineffective at later stages of growth

Low Risk Traits:

• A temperate weed that may only be a threat at higher elevations
  
• Unarmed (no spines, thorns, or burrs)
  
• Palatable to livestock (in spite of possible nitrate toxicity)
  
• Largely self-incompatible
  
• Certain herbicides may provide effective control