Acacia melanoxylon R.Br.

  • Authority

    Isley, Duane. 1973. Leguminosae of the United States: I. Subfamily. Mimosoideae. Mem. New York Bot. Gard. 25 (1): 1-152.

  • Family

    Mimosaceae

  • Scientific Name

    Acacia melanoxylon R.Br.

  • Description

    Species Description - Unarmed trees to 16 m. Twig tips and unfolding leaves canescent, but quickly glabrous; young twigs with light-colored flanges. Leaves simple, broadly ovate-elliptic to oblanceolate, (6-)8-15 cm long, (.5-) 1-2.5 cm wide, straight to asymmetric, 3-5 nerved and reticulate between, coriaceous, vaguely mucronulate or not. "Reversion" leaves not infrequent on young growth, these bipinnate with 6-8 pairs pinnae and 10-15 pairs leaflets. Flowers in cream-yellow heads 5-8 cm diam on peduncles 3-5 mm, 2-5 in short, axillary racemes. Legumes narrowly oblong, compressed but turgid, mostly curved through 180°-360°, 5-10 cm long, 5-6(-8) mm wide; valves coriaceous, brownish, separating and contorting at maturity. Funiculus red (pale orange on dried material), double-plicate on both sides of seed, thus partially or completely encircling it.

  • Discussion

    CN 2n = 26 (Tjio, 1948). The blackwood acacia becomes a larger tree than most others introduced in this country. Most herbarium specimens are from parks, but I have frequently seen the species in San Diego, Los Angeles and Santa Barbara in yards and along streets. Riedel (1957) questions its desirability in this role: “Too often used as a street tree . . . the tree is too greedy for use on any city property and can be only recommended for use in the far background . . . suckers will spring up one hundred feet from where the tree stood ... it is safest to avoid this tree.” Graham (1941) states that it is also grown in California for its wood “which makes excellent fuel and furniture” and that it is planted in erosion control programs. Although the blackwood acacia in life is a rather distinctive species, herbarium specimens are frequently marked under other names. The following key distinguishes A. melanoxylon and species with which it is confused in the United States (as to material I have seen).

  • Distribution

    Urban California; occasional in Florida and elsewhere in conservatories. Cultivated as a street tree, slightly escaped. Nov.-March. Blackwood acacia. Native of Australia.

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