From Common Forest Trees of Hawaii

Blackwood Acacia
Acacia melanoxylon
Pea family (Fabaceae)

Post-Cook introduction

Blackwood acacia, or Australian blackwood, is an tree introduced in forestry tests and as an ornamental. It differs from the native koa, Acacia koa, in that its “leaves” are shorter and less curved, and its pods are narrow and curved. Mimosa subfamily (Mimosoideae).


©2010 Anthony Valois and the National Park Service
Medium-sized tree 40 ft (12 ) high and 1 ft (0.3 ) in trunk diameter. In southeastern Australia, where it is native, this acacia is a large tree to 80–110 ft (24–30 ) in height and 2½–4 ft (0.8–1.2 ) in diameter. With straight axis, erect branches, and narrow of dense foliage. Bark gray, rough, finely furrowed. Twigs slender, slightly angled, with tiny pressed hairs, brownish.

Leaves modified as sickle-shaped flattened leaf-stalks or (phyllodes) narrowly sickle-shaped or lance-shaped, slightly curved, 2½–4½ inches (6–12 ) long and 3⁄8–3⁄4 inch (1–2 ) wide, thickened and leathery, hairless, long-pointed at both ends, with dot-like near almost stalkless base, with 3–6 fine parallel veins from base, dull green. Leaves of young plants (juvenile) are (), to 5 inches (13 ) long, with 4–10 pairs of branches, each with 15–20 pairs of oblong thin dull green 3⁄8–1⁄2 inch (10–13 ) by 1⁄8 inch (3 ).

Flower clusters () of 3–5 short-stalked light yellow balls (heads) 3⁄8–1⁄2 inch (10–13 ) in diameter at the leaf base. Flowers tiny, 30–50 stalkless in ball, consisting of cup-shaped 5- to 5 narrow petals united in lower part, many spreading thread like separate 1⁄4–5⁄16 inch (6–8 ) long, ending in dot and narrow with hairy one-celled and threadlike

(pods) are oblong, narrow, 3–5 inches (7.5–13 ) long and less than 3⁄8 inch (1 ) broad, flat with thick borders, reddish brown, curved and twisted. Seeds 6–10, beanlike elliptical, 3⁄16 inch (5 ) long, shiny black, hanging and encircled by red ringlike stalks.

The wood is golden brown to dark brown, sometimes tinged or streaked with red, with a beautiful figure very similar to koa. It is hard, moderately heavy, moderately strong and durable, works easily, turns well, and takes a high polish. The wood has been compared with black walnut, as has koa.

Known as blackwood or “hickory,” this species is one of the most ornamental Australian timbers, used principally for cabinet work, paneling, also veneer, split staves, and furniture. Wood of five trees grown at Kokee, Kauai, was tested in 1966 and found to be similar in density and appearance to koa, but with a somewhat higher shrinkage in drying.

Propagated from seed, also by root sprouts. Relatively slow growing. Elsewhere planted as a street tree and ornamental, though not recommended for Hawaii for these purposes because of the root suckering problem. Introduced also in California where it grows very well as a street tree. A total of 17,000 trees were planted in the Forest Reserves before 1960. Since 1960 several large plantings have been made in the Waiakea Forest Reserve on Hawaii, but the trees there are slow growing.

Special area
Kokee

Champion
Height 78 ft (23.8 ), c.b.h. 8.2 ft (2.5 ), spread 57 ft (17.4 ). Kokee State Park, Kauai (1968).

Range
Native of southeastern Australia

Other common names
Australia blackwood, blackwood, black acacia

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

cm -- A centimeter which is about 0.4 inches.

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

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

petiole -- the stalk of a leaf.

style -- This is a long and thread-like structure that connects the stigma with the ovary. A flower may have a single style, or several of them.

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

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

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

A raceme is an unbranched, indeterminate type of inflorescence bearing flowers having short floral stalks along its axis.

A pistil is the female structure of many flowers. It contains one or more carpels. Each carpel contins an ovary, style and stigma. The stigma receives the pollen which grows thru the style to reach the ovary.

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

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

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

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

A leaf is compound when multiple leaflets are on the same stem.

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.

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

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

In regular flowers all parts of the flower are similar in size and arrangement. Symeteric.

An ovary is a part of the female reproductive organ of the flower. Above the ovary is the style and the stigma, which is where the pollen lands and germinates to grow down through the style to the ovary.