Acacia dealbata Link

  • 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 dealbata Link

  • Description

    Species Description - Unarmed shrub or tree to 15 m. Young twigs and leaf rachises velutinous, the branchlets glaucous as pubescence thins; leaflets puberulent beneath or on both surfaces. Leaves bipinnate, silvery-grayish to green, sometimes slightly golden when unfolding; rachis with glands between pairs of pinnae but interjugary glands lacking; pinnae (10-) 13-21 pairs; leaflets crowded, intervals less than width of leaflets, 28-40 pairs, slenderly oblong, (2-)2.6-3.5 mm long, .4-.5 mm wide, (4.5-)6-7 r. Flowers in shortly peduncled (ca 3 mm) bright yellow or orange-yellow heads, 6-7 mm diam, in axillary racemes or terminal panicles. Legume oblong, laterally compressed, (3-)5-8 cm long, 7-9(-12) mm wide; margins scarcely constricted; valves papery, glabrous, often glaucous, reddish brown or blackish. Funiculus extending ca 90° about seed, arillate.

  • Discussion

    A. decurrens var. dealbata (Link) F. Muell. A. decurrens var. mollis auct. pro parte A. decurrens auct. pro parte A. mollissima auct. pro parte CN 2n = 26 (Atchison, 1948). Acacia dealbata is enumerated in the usual listings, commonly as a variety of A. decurrens Willd. Riedel (1957) says its introduction into California dates back to 1860. Acacta dealbata, A. mearnsoi and A, decurrens are related and classically have been treated as varieties of the latter. The first two are much confused as to horticultural designations and in herbaria in the United States. Some material may be intermediate. Breeding investigations have shown them to be interfertile (Phillip & Sherry, 1949), and some horticultural forms have been said to be hybrids (Cheel, 1935). Contrariwise, Tindale (in litt.) states “The only two species of this group which hybridize to any extent here (Australia) are A. decurrens and A. baileyanna. They do not grow together otherwise and would not have any opportunity to hybridize.” However, physical isolation is eliminated in horticultural situations. My key characters distinguishing these species are similar to those of Tindale (1962), but American specimens show more overlap in leaflet number than her Australian ones. I note that the unfolding leaves of some material of A. dealbata are slightly tawny to pale lemon yellow; previous American authors have attributed this feature (golden hairs) only to A. mearnsii. Acacia dealbata is considerably the most common of this group in cismontane California. It is aggressive in cultivation, spreading and establishing itself. Jones (1933) observes that its roots readily clog drain pipes and that it is not a favorite street tree.

  • Distribution

    Cismontane, mostly urban California (one specimen from Florida). Cultivated ornamental, moderately escaped and even weedy. Jan.-March and sporadically throughout the year. Silver wattle. Native of Australia but established in warm areas in Asia and Africa.

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