Family: Asteraceae

Origin, Description & Uses
The sunflower (Helianthus annuus) is native to North America and is widely recognized for its large, bright yellow flower heads and tall, sturdy stems. It is an annual plant that can grow several feet tall, producing seeds that are harvested for food, oil, and bird feed. Sunflowers are also popular in gardens and landscapes for their striking appearance and ability to attract pollinators, making them both a functional and ornamental plant.

Risks & Threats
Sunflowers are naturalized on Maui and Hawai‘i, sunflowers possess traits that raise concern for tropical island ecosystems. They can spread easily from cultivation, potentially competing with native plants and altering habitats. Because sunflowers are a valued crop, it is important to manage them carefully to minimize escape and prevent uncontrolled spread. Gardeners and farmers are encouraged to monitor plantings closely and prevent seeds from dispersing into natural areas.

High Risk Traits:

• Naturalized outside native range
  
• Known as a weed of agriculture, pastures, and disturbed areas (reduces crop yields)
  
• Noxious weed in several U.S. states
  
• Congeneric species are weedy
  
• Allelopathic (inhibits other plants)
  
• Forms dense stands
  
• Hybridizes naturally with other species
  
• Prolific seed production (1,000–4,000 seeds per head)
  
• Seeds dispersed by birds, animals, and water; also a produce contaminant
  
• Tolerates a wide range of conditions (drought, poor soil, many soil pH levels)

Low Risk Traits:

• No spines, thorns, or burrs
  
• Palatable to grazing animals
  
• Not shade tolerant
  
• Intolerant of acidic or waterlogged soils
  
• Primarily self-incompatible (requires cross-pollination)
  
• No vegetative reproduction
  
• Limited wind dispersal (seeds heavy)
  
• Seeds do not survive gut passage (mostly eaten)
  
• Effective natural enemies present (e.g., birds)