Family: Asteraceae

Origin, Description & Uses
Picris hieracioides (hawkweed, hawkweed oxtongue) is a flowering plant native to temperate regions of Eurasia. It is an upright, branching herb in the daisy family with rough, hairy leaves and bright yellow dandelion-like flowers. The species commonly grows along roadsides, disturbed areas, pastures, and open fields. In some regions it has been used as a minor forage plant or grown unintentionally as part of wildflower mixtures, though it is generally regarded as a weed rather than an ornamental species. In Hawaiʻi, it has become naturalized on Kauaʻi, Molokaʻi, Lānaʻi, Maui, and Hawaiʻi Island.

Risks & Threats
This species is naturalized in Hawaiʻi and possesses traits that are cause for concern in tropical island ecosystems. Picris hieracioides produces numerous wind-dispersed seeds, can establish quickly in disturbed habitats, and may spread into pastures, roadsides, and natural areas where it can compete with desirable vegetation. Its ability to colonize open environments increases the risk of further spread and long-term persistence. Because invasive plants can negatively affect native biodiversity and ecosystem function, planting or intentionally spreading this species is not recommended.

High Risk Traits:

• Elevation range exceeds 3000 m, demonstrating environmental versatility
  
• Able to grow in temperate and tropical climates
  
• Naturalized on Hawaii, Maui, Lanai, and Molokai and widely naturalized elsewhere
  
• A weed of disturbed sites, and possible weed of agriculture
  
• Other Picris species have become invasive
  
• Unpalatable to grazing animals
  
• Host of olive pathogen
  
• Tolerates many soil types
  
• Reproduces by seeds
  
• Seeds dispersed by wind, water, animals (externally) and as a seed contaminant
  
• Prolific seed production
  
• Some seeds may persist in the soil for up to 5 years

Low Risk Traits:

• Unarmed (no spines, thorns, or burrs)
  
• Requires full sun
  
• Self-incompatible
  
• Not reported to spread vegetatively
  
• Herbicides may provide effective control
  
• Mechanical methods provide effective control