Family: Ulmaceae

Origin, Description & Uses
Ulmus pumila, commonly known as Siberian elm, is a fast-growing deciduous tree native to Central Asia, southern Siberia, Mongolia, northern China, and Korea. It is highly adaptable and tolerates drought, poor soils, wind, temperature extremes, and urban conditions, making it a popular choice for windbreaks, shelterbelts, erosion control, shade, and landscaping in many parts of the world. Siberian elm typically reaches 30–70 feet (9–21 m) in height and has an open, rounded crown with small, serrated leaves, rough gray bark, and clusters of papery winged seeds that are produced in abundance each spring.

Risks & Threats
Although Ulmus pumila is not currently known to be naturalized in the Hawaiian Islands, it possesses several traits that are cause for concern. This species grows rapidly, begins producing large quantities of wind-dispersed seeds at a young age, readily establishes in disturbed habitats, and can also spread by stump sprouts and root suckers. In many regions outside its native range, it has escaped cultivation and formed dense stands that outcompete native vegetation, alter plant communities, and invade grasslands, riparian areas, and other open habitats. Because these characteristics could allow it to spread and negatively impact tropical island ecosystems if introduced more widely, Plant Pono recommends choosing a low-risk or native alternative whenever suitable options are available.

High Risk Traits:

• Broad climate tolerance (zones 4–9; 50–2400 m elevation)
  
• Repeated introductions outside native range
  
• Naturalized in the U.S.
  
• Agricultural weed – forms dense thickets, reduces forage
  
• Environmental weed – invades prairies, stream banks; noxious in New Mexico
  
• Congeneric weeds exist (Ulmus spp.)
  
• Forms dense thickets
  
• Creates fire hazard (brittle branches, litter buildup)
  
• Tolerates poor, dry, and heavy soils
  
• Produces viable seed with high germination
  
• Hybridizes with native elms
  
• Self-compatible (hermaphroditic, wind-pollinated)
  
• Intentionally spread by humans (ornamental, windbreaks, lumber)
  
• Wind-dispersed seeds
  
• Prolific seed output (>1000 seeds/m²)
  
• Resprouts after cutting or damage

Low Risk Traits:

• Not tropical/subtropical native
  
• No spines, thorns, or burrs
  
• Not allelopathic or parasitic
  
• Non-toxic to animals and humans
  
• No major economic pest/pathogen issues
  
• Not shade-tolerant (requires full sun)
  
• No vegetative spread
  
• No water, bird, or animal dispersal
  
• No persistent seed bank (<1 year viability)
  
• Well-controlled by herbicides