Family: Fabaceae

Origin, Description & Uses
Spanish broom (Spartium junceum) is a large, fast-growing shrub native to the Azores and the Mediterranean region of southern Europe. It is characterized by slender green stems, sparse leaves, and abundant, fragrant bright yellow flowers that bloom over a long season. Spanish broom is widely cultivated as an ornamental plant for its showy floral display and drought tolerance. It has also been used for erosion control, landscaping in dry environments, and historically as a source of fiber for cordage and textiles.

Risks & Threats
Spanish broom is potentially naturalized on Kaua’i and possesses traits that are cause for concern in tropical island ecosystems. It produces large numbers of seeds, can form dense stands, and is well adapted to dry, disturbed habitats where it may outcompete native vegetation and alter natural plant communities. Its ability to establish and spread beyond cultivation increases the risk of invasion, particularly in open or degraded areas. Because of these characteristics, Spanish broom could detrimentally impact biodiversity and ecosystem function. Where possible, gardeners and land managers are encouraged to select low-risk or native alternatives. In areas where Spanish broom is already established, efforts should focus on preventing further planting and limiting its spread into new locations to minimize additional environmental impacts.

High Risk Traits:

• Naturalized extensively beyond native range (Mediterranean, California, Hawaii, Britain).
  
• Potentially naturalizing on Kaua'i
  
• History of repeated introductions for ornamental and practical use.
  
• Classified as an environmental weed and noxious weed in several regions.
  
• Reaches reproductive maturity in 2–3 years.
  
• Prolific seed production (up to 10,000 seeds/plant/season).
  
• Forms persistent seed bank (viability ≥ 5 years).
  
• Forms dense, fire-prone thickets that displace native vegetation.
  
• Seeds dispersed by water, ants, machinery, contaminated soil, and intentional human planting.
  
• Tolerates a wide range of soil types and drought.
  
• Resprouts vigorously after cutting, mowing, or root damage.
  
• Capable of natural hybridization with related broom species.
  
• Toxic to humans (especially seeds; affects central nervous system).

Low Risk Traits:

• No vegetative reproduction (spreads only by seed).
  
• Not toxic to animals.
  
• Not unpalatable to all grazers (eaten by sheep/goats).
  
• Well-controlled with glyphosate and other herbicides.