[Mimosa leucocephala Lam.; Acacia glauca sensu Willd., non (L.) Moench; Leucaena glauca (L. ex Willd.) Benth.; Mimosa glauca sensu L. (1763), non L. (1753)]
(nat) Koa haole, ekoa, lilikoa
Shrubs or small trees usually up to 9 m tall (maximum size recorded 20 m tall). Leaves with (2)3-8 pairs of pinnae, leaflets (5—)7—17(—21) pairs per pinna, subopposite, obliquely narrowly ovate, 6-19 mm long,1.5-5mm wide, puberulent on margins and sometimes along midrib, apex acute. Flowers pale green or white, 4-5.5 mm long, in heads up to 13 mm in diameter in bud, peduncles 1-2 per leaf axil, 2-5 cm long; stamens ca. 7 mm long. Pods linear- oblong, 8-18(-20) cm long, (1.5—)2 cm wide, glabrous or puberulent, on a stipe up to 3 cm long. Seeds glossy brown, ellipsoid or ovoid, laterally flattened, 6-9 mm long, 3.5-5.5mm wide, 0.8-2 mm thick, with a pleurogram ca. 4 mm long and 1.5 mm wide. [2n = 36, 56, 104*.] Native to the Neotropics, cultivated for various purposes such as fodder, firewood, erosion control, soil improvement, shade trees for coffee or cocoa plantations, and seeds for necklaces, easily escaping and now widely naturalized throughout the tropics; in Hawaii naturalized and very common, sometimes forming the dominant element of the vegetation, in low elevation, dry, disturbed habitats, 0- 350 m, on Midway Atoll and all of the main islands. First collected on 0‘ahu or Kauai in 1837 (Barclay s.n., BM). A heavy infestation of a Caribbean psyllid insect [Heter- opsylla cubana (Crawford)], first observed in Hawaii in 1984, has caused much defoliation of koa haole (Beardsley, pers. comm.). —Plate 92.
This plant is rich in proteins (27-34% of dry weight). About 5 % of the protein of the leaflets consists of mimosine, an amino acid. When Leucaena makes up more than half of the diet of cattle for more than 6 months, general ill health and loss of hair may result. Other domestic animals are even less tolerant to mimosine.
The correct name for this species has had a complex history (de Wit, 1961, 1975; Gil- lis & Stearn, 1974; Polhill & Stearn, 1976). The binomial Mimosa glauca was used twice by Linnaeus, in 1753 and 1763, for 2 different plants. The 1753 usage is referable to Acacia glauca (L.) Moench, whereas the 1763 usage was the basis for binomials by Willdenow and Bentham; however, the epithet “glauca” can not be used because of the earlier 1753 usage. The earliest available epithet is that of Lamarck. The name Leucaena latisiliqua (L.) Gillis was applied to L. leucocephala briefly by Gillis and Stearn (1974); however, their typification was incorrect. The basionym Mimosa latisiliqua L. represents a species of Lysiloma, correctly called Lysiloma latisiliqua (L.) Benth.
The chromosome report of 2n = 56 for this species is almost certainly an error. It is probably based on an incorrect identification of voucher material.