Family: Fabaceae

Origin, Description & Uses:
Lysiloma watsonii, commonly known as lysiloma, is a small to medium-sized tree native to southern Arizona and northern Mexico. A member of the legume family, it features an airy, spreading canopy with delicate, fern-like foliage that provides light, dappled shade. The tree produces small, cream-colored, puffball-like flowers that attract pollinators, followed by slender seed pods. Well adapted to warm, dry climates, Lysiloma watsonii is commonly used as an ornamental or shade tree in xeriscaping and low-water landscapes. It is especially valued for its drought tolerance, graceful form, and ability to improve soil fertility through nitrogen fixation.

Risks & Threats:
Lysiloma watsonii is considered a low-risk species, with no significant evidence of invasiveness or ecological harm where it is grown. It does not typically spread aggressively, and its growth and reproduction are generally manageable in cultivated settings. While any introduced species should be monitored for unexpected spread, this species has not shown a tendency to naturalize widely or disrupt native ecosystems. When planted thoughtfully, lysiloma is a safe and attractive option for landscaping, with minimal risk to surrounding environments.

High Risk Traits:

• Nitrogen-fixing (can alter soil nutrients)
  
• Tolerates poor soils
  
• Produces viable seed
  
• Seeds have physical dormancy (hard seed coat, persistent seed bank)
  
• Intentionally dispersed by people (ornamental planting)
  
• Fast growth with water (minimum generative time ~3 years)

Low Risk Traits:

• No evidence of naturalization beyond native range
  
• No reports as a weed (environmental, agricultural, or garden)
  
• No spines, thorns, or burrs
  
• No evidence of toxicity to humans or animals
  
• Not shade tolerant (requires full sun)
  
• No vegetative fragmentation
  
• Large pods and seeds (not easily dispersed by wind, water, or externally by animals)
  
• Not bird-dispersed
  
• No evidence of dense thicket formation