Family: Fabaceae

Origin, Description & Uses
Chamaecytisus proliferus subsp. palmensis, commonly known as broom, tagasaste, or tree-lucerne, is a fast-growing shrub or small tree native to the Canary Islands. It typically grows 10–20 feet tall and features soft, gray-green, three-part leaves and clusters of small white, pea-like flowers. As a legume, it fixes nitrogen in the soil, allowing it to grow in nutrient-poor and disturbed areas. Tagasaste has been widely planted in dry regions as a high-protein forage crop for livestock, as well as for windbreaks, erosion control, and soil improvement. Its drought tolerance and rapid growth have made it popular in agricultural and agroforestry systems.

Risks & Threats
In Hawaiʻi, tagasaste is naturalized on Maui and Hawaiʻi Island. Although useful in agricultural settings, this species possesses traits that are cause for concern, including fast growth, abundant seed production, and the ability to spread in dry, open habitats. Its nitrogen-fixing capacity can change soil conditions, potentially favoring invasive species and disadvantaging native plants adapted to low-nutrient soils. Dense stands may outcompete native vegetation and alter ecosystem processes, including increasing fire risk in dry landscapes. Because it is naturalized and could detrimentally impact tropical island ecosystems, Plant Pono recommends choosing a low-risk or native alternative for landscaping and restoration projects.

High Risk Traits:

• Grows in regions with Mediterranean to subtropical climates
  
• Naturalized on Maui and Hawaii islands, and elsewhere
  
• Environmental weed in Australia
  
• Other Cytisus species are invasive
  
• Seeds reported to be toxic
  
• Tolerates many soil types
  
• Reported to form dense stands in Australia
  
• Nitrogen fixing (may allow invasion by other weeds)
  
• Reproduces by seeds
  
• Self-compatible
  
• Reaches maturity in 3 years
  
• Seeds explosively released from pods
  
• Seeds also may be dispersed by ants, birds, dumped garden waste
  
• Forms a long-lived seed bank
  
• Able to resprout after cutting and browsing, tolerates fire

Low Risk Traits:

• Unarmed (no spines, thorns or burrs)
  
• Provides fodder for livestock (palatable despite reports of possible toxicity)
  
• Not reported to spread vegetatively
  
• Herbicides may provide effective control