From Common Forest Trees of Hawaii

Black Wattle
Acacia mearnsii
Pea family (Fabaceae)

Post-Cook introduction

This is a small, handsome, introduced tree with a thin spreading of finely divided leaves, flowers in small light yellow balls, and narrow flattened beadlike pods. To 40 ft (12 ) tall and 10 inches (25 ) in trunk diameter. Bark brown to gray, smooth to finely fissured. Inner bark is light yellow with brown steaks, bitter. Twigs brownish, finely angled, with tiny hairs.


©2013 J. B. Friday
Leaves finely divided, twice (), 3–6 inches (7.5–15 ) long, with tiny hairs and slender angled axis. Side axes 4–15 pairs, very slender, with dot-like at base of each pair. are very numerous, 30–80 crowded featherlike on each axis, not paired, stalkless, very narrow (linear), 3⁄16–3⁄8 inch (5–10 ) long, gray green to dark green.

Flower clusters of light yellow balls (heads) 1⁄4 inch (6 ) in diameter, several on short stalks at leaf bases and shorter than leaves. Flowers fragrant, tiny, numerous stalkless in balls, 1⁄8 inch (3 ) long, with tiny five- and and many spreading threadlike separate ending in dot

(pods) are several clustered, 2–4 inches (5–10 ) long, 1⁄4 inch (6 ) wide, flattened, gray brown to blackish, finely hairy, slightly narrowed between seeds, splitting open. Seeds are several, beanlike, 1⁄8 inch (3 ) long, elliptical, dull black.

The wood is light brown with reddish streaks resembling pale koa. It is heavy ( gr. 0.55), hard, and relatively difficult to work. It is not resistant to decay. Elsewhere, the wood is used in turnery and for fuel, and the bark for tanning. It is not used in Hawaii.

Considered a weed in most places in Hawaii, particularly in Kula, Maui, where it is very prolific. Propagated from seeds and easily established. Short-lived, but new sprouts are produced by roots. The Division of Forestry has planted 65,000 trees in the Forest Reserves, primarily at Mokuleia, Oahu and Kula, Maul. The trees at the Kula Forest Reserve were mostly planted in 1938 and 1939 and may be the progenitors of the escapes. Also at Kamuela, Hawaii. Introduced as an ornamental in southern California and other subtropical regions.

Special areas
Kokee, Kula, Tantalus

Range
Native of Australia

Other common names
green-wattle acacia, blackwattle, green-wattle

This species was formerly called Acacia decurrens (Wendl.) Willd.

An evergreen tree retains a large portion of its green leaves all year.

stamen -- the pollen-producing reproductive organ of a flower; The stamen consists of an anther supported by a filament.

corolla -- The name for all the petals of a flower taken together.

cm -- A centimeter which is about 0.4 inches.

mm -- millimeter. About 1/25th of an inch.

alternate -- leaves alternate along the main stem and are attached singly.

calyx -- the sepals of a flower, typically forming a whorl that encloses the petals and forms a protective layer around a flower in bud.

m -- A meter is about 10% larger than a yard.

A noxious weed is considered to be harmful to the environment or animals. Often a governing body designates plants as noxious.

Glands are plant structures that secrete liquids, salts or other substances. Glands often appear as hairs with a drop of liquid at the end.

Like the teeth on a saw, leaves and other surfaces can have toothed edges.

fruit -- any seed-bearing structure in flowering plants. It is formed from the ovary after flowering.

pinnate -- A compound leaf with two rows of leaflets.

The anther is a pad at the end of the stamen that holds the pollen.

sp. -- The abbreviation for "species". The plural is "spp". When used it sometimes means that the exact species is unknown. For example, "Aster sp" would mean some species within the Aster genus but the writer may not know exactly which species.

canopy -- The foliage of a tree; the crown. Also the upper layer of a forest.

leaflets -- Each little leaf-like thing in a compound leaf is a leaflet.

Bipinnate -- A compound leaf with two rows of leaflets where those leaflets are again compound with two rows of leafelets.