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Eucalyptus robusta Sm.

Myrtaceae
Swamp mahogany, Iron bark

Source: James A. Duke. 1983. Handbook of Energy Crops. unpublished.


  1. Uses
  2. Folk Medicine
  3. Chemistry
  4. Description
  5. Germplasm
  6. Distribution
  7. Ecology
  8. Cultivation
  9. Harvesting
  10. Yields and Economics
  11. Energy
  12. References

Uses

One of the most widely planted eucalypts, this has moderately hard and heavy wood (sp. grav. 0.51) which is strong but brittle and stiff, elastic, coarse-textured, and fairly straight-grained but with some interlocking. Difficult to season and split, it works well and takes a good polish, and is durable in contact with the ground. The wood is employed in general construction, for underground piling, utility poles, fenceposts, and firewood. An attractive ornamental honey-producing tree, it is also planted as a windbreak. The plant is used as an insecticide in China (Perry, 1980).

Folk Medicine

Reported to be preventitive, swamp mahogany is a folk remedy for abscesses, boils, cellulitis, colds, dysentery, encephalitis, enteritis, erysipelas, flu, gangrene, mastitis, and sores (Duke and Wain, 1981).

Chemistry

The kino contains the antibiotic citriodorol. Leaves and fruits were positive for flavonoids, sterols, and tannins. The bark contains only 1.4% tannin, while the leaves may contain 12% (Watt and Breyer-Brandwijk, 1962). Leaves contain 0.16% essential oil, with aromadendren (or aromadendral) and pinene.

Description

Evergreen tree 24–40 m with relatively large, short, straight, trunk 1–1.2 m in diam. ca half the height of the tree. Trunk may have air roots. Bark gray or brown, reddish brown beneath surface, very thick, rough, deeply furrowed, fibrous. Leaves alternate, blades broadly lanceolate, 10–18 cm long, 3–6 cm wide, acuminate, acute at base and often with curved, unequal sides, glabrous, thick, leathery, stiff, shiny or dull dark green upper surface, dull light green beneath. Petiole to 25 mm, umbels single at leaf base, to 6 cm long, peduncle 2–3 cm. Flowers 5–10, equally short-stalked, large, 3 cm across. Buds pyriform, 12–20 mm long, 7–10 mm wide. Stamens many, threadlike, spreading, white or cream-colored, ca 12 mm long, anthers oblong with large oblong gland. Pistil with inferior 3–4-celled ovary and straight, stout style. Capsules several in rounded cluster, stalked, 12–15 mm long, 10–12 mm wide. Seeds tiny, dull light brown, 1–2 mm long (Little, 1983).

Germplasm

The hybrid with E. grandis is regarded as having better firewood potential.

Distribution

Native to southeastern Australia on a very narrow coastal strip (0–100 m elev.), but now widely introduced in tropical and subtropical areas. According to Little (1983), it is the best adapted species to Puerto Rico. Cultivated, for example, in Angola, Argentina, Arizona, Brazil, California, Cameroon, China, Congo, Costa Rica, Florida, Ghana, India, Indonesia, Israel, Ivory Coast, Malagasy, Malaysia, Mauritus, New Hebrides, Nigeria, Peru, Philippines, Puerto Rico, Sri Lanka, Tanzania, and Vietnam.

Ecology

Estimated to range from Tropical Dry to Moist through Frostfree Subtropical Very Dry to Moist Forest Life Zones, swamp mahogany is estimated to tolerate annual precipitation of 8 to 15 dm, annual temperature of 18 to 25°C, and pH of 5 to 7.5. Where native, this species is found mainly in swamps and at the edge of brackish estuaries. It grows better on slopes, but doesn't compete as well as the mixed forest species (Little, 1983).

Cultivation

Out of a gram of seed, about 100 germinate. Seed is usually sown, immediately after collecting and sundrying.

Harvesting

In Malaysia, it starts fruiting as early as year 4. Fruits take two years to ripen in China. Fruits are collected when the capsules start to turn black.

Yields and Economics

In Argentina, 5 year old stands 9 m tall (1,583 trees/ha) had a basal area of 10 m2 and a volume of 89 m3 for an average of 18 m3/ha/yr. Webb et al. (1980) report wood yields of 14–28 m3/ha/yr. In Malaysia, the MAI was 4 cm planted under shade, 6 planted in slash/burn situation, and 11 planted in an abandoned vegetable garden (Fenton et al., 1977).

Energy

Little (1983) mentions the use of the species for fuel, but it was not recommended by NAS (1980a). Planted for fuel reserves at 1,000–2,000 m elevation in Sri Lanka (MacMillan, 1925). Comparing potential energy trees for Panama, Curtis and Duke (1982) cite Puerto Rico studies showing green weight of 14,556 kg/ha for Eucalyptus robusta, 8,922 for Albizia procera, 6,932 for Casuarina equisetifolia, 4,360 for Leucaena (K-8), 599 kg only for native Leucaena, and only 402 for Cassia siamea. The data from Puerto Rico were provided by a team promoting energy grasses as energy sources. They concluded that energy grasses will produce 6–7.5 times more green biomass. They cited 53 MT for sordan, 82 for napier grass, and 84 MT/ha DM for sugarcane (in 12 months). Perhaps the data of Smith and Dowd, in Florida, are equally reliable. They projected only ca 6 MT/ha for Eucalyptus (perhaps E. grandis, robusta, or viminalis) with ca 60 for napier grass, 32–54 for sugarcane, and 16–37 for sorghum, only 22 for sordan. Both the Puerto Rican and Florida tabulations suggest that the energy grasses may be 10 times as productive of DM as Eucalyptus. Eucalyptus scored lower than Melaleuca on yield (ca 6 MT/ha/yr) and nothing has as high a heating value as the bark of Melaleuca (>25,000 kj/kg). The stemwood (density 0.53 g/cm3) ofi E. robusta had a heat value of 19,628 kj/kg, the stembark (0.22 g/cm3), 18,074 (Wang et al., 1982).

References

Complete list of references for Duke, Handbook of Energy Crops
Last update Tuesday, January 6, 1998 by aw