Family: Arecaceae

Origin, Description & Uses
Ptychosperma propinquum (cluster palm, hurricane palm, Macarthur palm) is a slender, clustering palm native to New Guinea and northern Australia. It is valued as an ornamental landscape plant because of its graceful form, smooth ringed trunks, feathery fronds, and ability to create a lush tropical appearance in gardens and urban plantings. This species is commonly used as a screening or accent palm in warm climates and performs well in moist, tropical environments. Its attractive growth habit and relatively fast growth have contributed to its popularity in cultivation throughout the tropics, including Hawaiʻi.

Risks & Threats
This species is naturalized on Oʻahu and possibly Kauaʻi, indicating that it is capable of spreading beyond cultivation in the Hawaiian Islands. Ptychosperma propinquum possesses traits that are cause for concern, including prolific seed production and the ability to establish in shaded, moist habitats. These characteristics could allow it to spread into natural areas where it may compete with native vegetation and detrimentally impact tropical island ecosystems. Because this palm is already established in parts of Hawaiʻi, planting should be managed carefully and avoided near forests, streams, and other sensitive habitats to help minimize further spread. When possible, choosing a low risk or native alternative is recommended to reduce the risk of additional environmental impacts.

High Risk Traits:

• Thrives in tropical climates
  
• Naturalized on Oahu, and possibly Kauai (Hawaiian Islands) and elsewhere
  
• Regarded as weedy and potentially invasive in a number of tropical locations (although impacts have not been described)
  
• Host of palm pests and pathogens
  
• Fruit an irritant and may cause dermatitis
  
• Shade tolerant
  
• Tolerates many soil types
  
• Reproduces by seeds
  
• Reaches maturity in 2-3 years
  
• Seeds dispersed by birds, possibly by water, and intentionally by people
  
• Prolific seedling production in some areas where naturalized

Low Risk Traits:

• Despite naturalization, negative impacts have yet to be documented
  
• Unarmed (no spines, thorns, or burrs)
  
• Not reported to spread vegetatively