Family: Fabaceae
An invasive tree, native to Taiwan and the Philippine islands. Due to catastrophic erosion in the early 1900s, Acacia confusa was imported to stabilize the soil. The Sugar Planters Association, along with the Board of Agriculture, planted 300,000 trees. Acacia confusa is widely naturalized in dry areas on all the main Hawaiian Islands.
The Division of Forestry and Wildlife of the Hawaiʻi Department of Land and Natural Resources has designated this species as one of “Hawaiʻi’s Most Invasive Horticultural Plants.”
Description and Dispersal:
- A branched tree 20 - 50 ft tall, resembles the native Acacia koa
- Somewhat sickle shaped narrow leaves (4 in long by 1/3 in wide)
- Flower clusters of yellow balls (1/2 in); flat linear seed pods are green to brown (4 in long by 1/2 in wide)
- Spreads by seeds
High Risk Traits:
- Widely naturalized in Hawaiʻi and other tropical/subtropical regions
- Considered a serious environmental weed in Hawaiʻi; shades out native vegetation
- Forms monotypic stands and can dominate disturbed to mesic habitats
- Exhibits allelopathic effects – soil and leaf extracts inhibit germination of other plants
- Toxic compounds present (including alkaloids like DMT) – unsafe for consumption
- Unpalatable to livestock and not suitable as fodder
- Nitrogen-fixing tree, which can alter soil chemistry and favor further spread
- Produces hard-coated seeds that persist in the soil for years and germinate after fire
- Resprouts vigorously after fire or cutting, making management difficult
- Propagated and spread intentionally by people for ornamental and reforestation purposes
- Hosts a wide range of fungal pathogens (potential plant health risk)
Low Risk Traits:
- Does not produce spines, thorns, or burrs
- Not fire-promoting; stands are generally fire resistant
- Does not appear to be dispersed by wind, water, or animals (seeds are passively dispersed)
- Seed production is not extremely prolific (<1000/m²)
- Populations in some locations have been successfully controlled with herbicides
