Common Forest Trees of (Native and Introduced)

Silk- log. Suitable for face veneer as well as paper pulp. It has very long fibers for a hardwood. In Hawaii, the wood has robusta A. Cunn. been utilized for furniture, cabinetmaking, paneling, inte- riors, and in one entire house including the framing. family () The trees are propagated readily from the great quan- Post-Cook introduction tities of seeds, grow rapidly, and are drought resistant. Along the road to Kokee State Park, Kauai, trees are unhealthy Silk-oak, a handsome Australian tree planted for shade, with ragged crowns. Elsewhere, trees have full crowns. ornament, and reforestation, also widely naturalized, is Introduced into Hawaii about 1880 from Australia, it recognized by the pinnate and deeply lobed fernlike leaves, is now seen as a shade tree and street tree through the is- dark green above, silky with whitish or ash-colored hairs lands from sea level to 4000 ft (1219 m). This species is beneath, by the showy yellowish flowers clustered on I the second most commonly planted tree in Hawaii after side of slender stiff axes, and by black curved podlike fruits robusta eucalyptus, Eucalyptus robusta. It is hardy in dry with slender stalks and styles. soils, quick growing and pest-free. Although it has been Medium-sized to large deciduous tree 40Ð70 ft (12Ð planted mostly in drier areas, it does best where planted in 21 m) high and 1Ð3 ft (0.3Ð0.9 m) in trunk diameter with moist sites with 60Ð80 inches (1524Ð2032 mm) rainfall. straight axis and many branches, reported to reach 100 ft The trees scatter their winged seeds and have become un- (30 m) or more where native. Bark light gray, rough and desirable weeds in some pastures and rangelands of Ha- thick with many deep furrows, on branches gray and waii, requiring eradication. There are extensive natural- smooth. Inner bark with brownish layer and whitish within, ized stands on Kapapala Ranch in Ka‘u and Huehue Ranch fibrous, slightly bitter. Twigs stout, angled, with fine gray in North Kona. Hawaii has 3 million board feet of sawtim- pressed hairs. ber and Oahu 2.5 million, mostly in the Honouliuli Forest Leaves alternate pinnate, fernlike, 6Ð12 inches (15Ð Reserve. 30 cm) long, almost bipinnate, with 11Ð21 side axes (pin- In some countries, the trees have served as coffee shade. 1 1 nae) 1 ⁄2Ð3 ⁄2 inches (4Ð9 cm) long, deeply divided into nar- Some were planted for this purpose in Kona in the early 1 1 row long-pointed lobes ⁄4Ð ⁄2 inch (6Ð13 mm) wide, with part of the century. This species is classed as a honey . borders turned under, shiny and hairless above, slightly Planted for ornament and shade in central and southern thickened. Florida, where it is persistent but not naturalized. There it is Flower clusters (racemes) 3Ð7 inches (7.5Ð18 cm) long, recommended as a fast-growing flowering tree for well- unbranched, arise mostly from trunk, along twigs back of drained and sandy soils, being both cold hardy and drought leaves, and at leaf bases. Flowers numerous with long slen- resistant. Formerly planted in Puerto Rico, but now not used 3 3 der stalks ⁄8Ð ⁄4 inch (1Ð2 cm) long, crowded on one side because of susceptibility to scale insects. Introduced also in of axis. They are composed of four narrow yellowish se- southern Arizona and California. Northward in temperate 1 pals almost ⁄2 inch (13 mm) long, curved downward; no climates, as in continental United States, the fernlike petals; four stalkless inserted on sepals and oppo- are grown indoors in pots. site them; and pistil with stalk, ovary, long slender curved style, and enlarged stigma. Special areas: Waimea Arboretum, Kalopa, Tantalus Fruits podlike (follicles) are broad, slightly flattened, Champion leathery, with long slender curved style, splitting open on 1 3 1 Height 90 ft (27.4 m) c.b.h. 10.6 ft (3.2 m), spread 47 ft side, remaining attached. Seeds one or two, ⁄8Ð ⁄2 inch (10Ð (14.3 m). State Forestry Arboretum, Hilo, Hawaii (1968). 13 mm) long, elliptical, flattened, winged, brown. Flower- ing from April to autumn, but predominantly AprilÐMay. Range The pale pinkish brown wood is attractive because of Native of Australia but widely introduced and naturalized the prominent rays, resembling oak, as the common name in tropical and subtropical regions of the world. suggests. This was the former “lacewood” of world trade until it became scarce in Australia. It is of moderate den- Other common names sity (sp. gr. 0.57), has low radial but high tangential shrink- silver-oak, ‘oka kilika, ha‘iku ke‘oke’o (Hawaii); roble de age in drying and is one of the best woods in all-around seda, roble australiano (Puerto Rico); grevilea (Spanish) machinability ever tested by the Forest Products Labora- Botanical synonym tory. Sawdust causes dermatitis to fairskinned people. The Stylurus robusta (A. Cunn.) Deg. wood is not resistant to decay or termites, and sapwood is Grevillea was dedicated to Charles Francis Greville highly susceptible to ambrosia beetle attack while in the (1749Ð1809), British horticulturist.

This information is from Agriculture Handbook no. 679 by Elbert L. Little Jr. and Roger G. Skolmen, published by the Forest Service, U.S. Dept. of Agriculture, in 1989. Its present format is that of a reprint version published by the College of Tropical Agriculture and Human Resources, University of Hawaii at Manoa, 2003. Common Forest Trees of Hawaii (Native and Introduced)

Silk-oak Grevillea robusta A. Cunn. 1 Flowering twig, ⁄2 X; flowers (lower left) and 2 fruit and seeds (lower right), ⁄3 X (P.R. v. 2).

This information is from Agriculture Handbook no. 679 by Elbert L. Little Jr. and Roger G. Skolmen, published by the Forest Service, U.S. Dept. of Agriculture, in 1989. Its present format is that of a reprint version published by the College of Tropical Agriculture and Human Resources, University of Hawaii at Manoa, 2003.