|Leucaena leucocephala (Lam.) de Wit|
This thornless tree forms dense thickets, excluding all other plants. It is grown for fodder, but unless severely grazed or controlled, it spreads rampantly throughout adjacent areas. The seeds are not actively dispersed except occasionally by rodents and alien granivorous birds. It regenerates rapidly from basal shoots after fire. There is also a flush of new seedlings produced following fire, but whether this is the result of normal germination or breaking dormancy by fire is not known. In mature monotypic stands fire is suppressed because of the low fuel load. The potential for biological control has been evaluated by Gardner and Davis (1982), but no action is likely to be taken because of its use in agriculture and use of closely related species as fuel crops. In fact, the State Department of Agriculture may import parasites of the recently introduced Heteropsylla cf. incisa (Nakahara and Lai 1984) which has considerable potential as a control agent of koa haole.
Koa haole is found in dry to mesic habitats on all islands up to 700 m, having been deliberately broadcast over lowland habitats approximately 50 years ago. It is also present in severely disturbed wet areas but not as a dominant species.