Family: Fabaceae
An ornamental tree that spreads from original plantings. Native to the wet tropical forests of Central America, Calliandra houstoniana var. calothyrsus thrives on the windward sides of the island chain. It is currently invading parts of Kauaʻi, Lanai, Maui, and Hawaiʻi Island. The weedy shrub aggressively colonizes disturbed areas, forming monotypic stands that both shade out and outcompete with native and more desirable plants. An alarming characteristic, as Calliandra houstoniana var. calothyrsus is in the horticultural trade and is used in landscaping statewide.
Propagules are spread short distances by ballistic explosions of seeds and by the wind. The nitrogen-fixing tree can be self-compatible, needing only one plant to reproduce successfully, and it reaches reproductive maturity in one year.
Description and Dispersal:
- Large shrub to small tree consisting of multiple stems
- Leaves are composed of smooth, green leaflets-typical of the Fabaceae family
- Red flowers, composed of showy stamens, are feathery in appearance
- Fruits are flattened, long brown pods containing 3 to 15 dark brown seeds
High Risk Traits:
- Thrives in tropical climates
- Elevation range exceeds 1000 m
- Naturalized on Kauai, Lanai, Maui, Hawaii and elsewhere
- An agricultural and disturbance-adapted weed
- Potentially allelopathic
- Shade tolerant
- Tolerates many soil types
- Can from dense monocultures
- Hybridizes naturally
- Limited self-compatibility
- Able to reach maturity in 1 year
- Seeds dispersed by explosive dehiscence of pods, and moved further by water and people
- Tolerates repeated cutting and browsing, and coppices vigorously
Low Risk Traits:
- Unarmed (no spines or thorns)
- Palatable to animals and an important fodder plant
- Seed set may be pollinator-limited
