Family: Caprifoliaceae

Origin, Description & Uses
Leycesteria formosa (Himalaya honeysuckle) is a fast-growing shrub native to mountainous regions from northeastern Pakistan through south-central China and northern Myanmar. It is recognized for its arching, bamboo-like hollow stems, lush green foliage, and distinctive drooping clusters of white to purple bracts that surround small flowers, followed by dark purple to black berries. Commonly grown as an ornamental plant, it is valued in temperate gardens for its unusual flowers, wildlife appeal (especially to birds), and ability to quickly establish in a variety of soil conditions.

Risks & Threats
Although Leycesteria formosa is currently not known to be naturalized in the Hawaiian Islands, it possesses traits that are cause for concern in tropical island ecosystems. It produces abundant, bird-dispersed seeds and can grow rapidly, allowing it to form dense thickets that may compete with and displace native vegetation, particularly in disturbed or riparian areas. Its adaptability and shade tolerance increase its potential to spread if introduced. Because of these characteristics, this species could negatively impact native biodiversity if it becomes established. For planting in Hawaiʻi, it is recommended to choose a low-risk or native alternative that supports local ecosystems and reduces the chance of future invasiveness.

High Risk Traits:

• Environmental weed in New Zealand, Tasmania, Macaronesia (top 100)
  
• Broad climate tolerance (native to 1100–3500m; naturalized worldwide)
  
• Forms dense, impenetrable thickets
  
• Shade tolerant
  
• Wide soil tolerance (sandy, clay, poor, alkaline, etc.)
  
• Prolific seed production (hundreds to seeds/plant; ~71 seeds/fruit)
  
• Vegetative reproduction (stem layering, root fragments, stem pieces)
  
• Reproduces within 2 years
  
• Dispersed by birds, water, deer, foxes, machinery, soil, garden waste
  
• Seeds survive gut passage (birds, mice, rats, possums, deer)
  
• Intentionally cultivated as ornamental
  
• Tolerates mutilation/cutting (regrows from rootstock)

Low Risk Traits:

• No spines, thorns, or burrs
  
• No evidence of allelopathy, parasitism, or toxicity to animals/humans
  
• Not wind-dispersed (berries)
  
• No external animal dispersal (endozoochory only)