Native to Asia, the Gunpowder Tree (Trema orientalis) was imported to Hawaiʻi before 1870. An estimated 31,000 trees were planted throughout the island chain, starting in 1925. It is a pest on all of the main Hawaiian Islands and is a very common sight in Hilo and Puna.
A fast-growing tree, the Gunpowder Tree reaches reproductive maturity in 2 to 3 years. It can grow from vegetative cuttings and by seed. Birds eat the fruit and are a significant disperser of seeds. It quickly colonizes disturbed areas, even in poor soil. It has an extensive root system that helps the tree in times of drought; unfortunately, that root system often grows into septic pipes, ruining the flow of the system.
- Naturalized on main Hawaiian Islands, Florida and possibly elsewhere
- A weed of disturbed forests and pastures
- A weedy tree of plantations and orchards
- Potentially allelopathic
- Host of pathogens
- Potentially causes eczema when handling
- Tolerates many soil types
- Reproduces by seeds
- Fast growth rate
- Seeds dispersed by birds and intentionally by people
- Coppices vigorously
- A tree growing up to 100 feet with slightly buttressed roots or swollen base
- Green leaves are alternately arranged, are ovate, are hairy, and have toothed margins
- Inconspicuous flowers are clustered at leaf nodes in dense bunches
Gunpowder Tree (Trema orientalis)
Photos (L-R): BIISC, Forest & Kim Starr, Forest & Kim Starr
Controlling Gunpowder Tree
Physical control: Physical removal is difficult. Gunpowder comes back vigorously after cutting. Cut mature trees and repeat as needed. Multiple stems will regrow from the stump. Dispose of green waste to prevent vegetative reproduction. Hire a licensed arborist for large trees.
Directions: Using a hatchet or machete, make incisions or ‘hacks’ at a 45-degree angle into the sapwood. At about waist high, make a hack every 2 inches around the trunk to make a circle. Apply .5 ml of undiluted herbicide into each hack. In BIISC’s herbicide trials, all three herbicides proved to be effective. Trees were 100% defoliated after 180 days after herbicide application.