Family: Urticaceae

An invasive tree that is native to Central America, Mexico, and South America, Cecropia obtusifolia, commonly known as trumpet tree, is invasive in other Pacific islands and parts of West Africa. The trumpet tree was likely imported for forestry plantings due to its fast growth and prolific seed production.

It’s unknown exactly when trumpet trees were introduced to Hawaii. The first naturalization record was in 1926, indicating the species had been reproducing here for years. Trumpet tree seedlings were planted, starting in 1927, in forest reserves throughout Hawai’i. Seeds were dispersed aerially over Panaewa in 1928 to reforest the area devastated by a big fire.  Today, there is a significant invasion of trumpet trees in the Puna and Hilo. The trumpet tree has naturalized on all the main Hawaiian Islands except Maui.

Considered a pioneer species in its homeland, the trumpet tree aggressively colonizes disturbed sites.  Each female tree can produce nearly one million seeds per season! Many animals help disperse the seeds, including insects, reptiles, birds, and mammals. The seeds attach externally to animals and survive passage through the gut. It forms monotypic stands preventing the establishment of native and other more desirable species. The tree is weak and easily breaks in storms, a common problem in fast-growing trees. Trees that break easily can close off roads, damage power lines, and be dangerous for humans in general. For all these reasons, trumpet tree is considered one of the worst 100 invasive trees worldwide.

 

Description and Dispersal:

• A short-lived softwood tree reaching heights of up to 30 feet
  
• Hollow trunk and stems are visibility segmented, much like bamboo
  
• Leaves are dull green on top and white/grey underneath, split into deeply palmate lobes (like a hand)
  
• Wind-pollinated small flowers are crowded on a stalk which grows from the axillary stem
  
• Dangling, finger-like fruit hangs below the leaf axil and is bird-dispersed

High Risk Traits:

• Broad climate adaptability – grows in varied tropical/subtropical conditions.
  
• Established invasive – naturalized in Hawaii and invasive on Rarotonga.
  
• Aggressive colonizer – quickly occupies disturbed areas.
  
• High seed production – up to ~900,000 seeds per tree.
  
• Animal-dispersed – seeds spread by birds, bats, and mammals.
  
• Forms thickets – can create monotypic stands.
  
• Related species invasive – congener (C. peltata) is invasive.

Low Risk Traits:

• Not toxic or allelopathic – safe for animals and humans.
  
• Shade-intolerant – requires open, high-light conditions.
  
• Dioecious – requires separate male and female trees.
  
• Seed-dependent – no vegetative reproduction.
  
• Short-lived seed bank – seed viability lasts only about 1 year.