Acacia cincinnata F. Muell

A. cincinnata grows up to 25 m tall and 40 cm diameter in moist parts in the tropics, but on drier sites of its natural range, it is a small tree less than 10 m in height. Bark compact, moderately hard, longitudinally fissured, grey-brown showing red-brown in the fissures. Young shoots covered with silky, golden yellow hairs, spines absent. Mature phyllodes bright green, oblong lanceolate or falcate, 10-16 cm long and 1.5-3 cm wide with 3 prominent longitudinal veins running into each other on the lower margin near the base. There is a prominent raised gland at the base of the phyllode. Flowers axillary spikes, 3-4 cm long, almost white to pale yellow and very faintly perfumed. Pods linear, spirally and tightly coiled and glaucous when immature. Seeds longitudinal in the pod, 3-5 mm long, 2-3 mm wide. The aril is large and open, and a rather fine yellow funicle encircles the seed. The generic name ‘acacia’ comes from the Greek word ‘akis’, meaning point or barb. The specific name is from the Latin ‘cincinnatus’, meaning ‘with curls’, and refers to the pods, which are spirally coiled. Its nearest relative is probably A. spirobis ssp. solandri. It is also closely related to A. polystachya, A. mangium and possibly A. auriculiformis.

Floral buds have been observed as early as 26 months in field trials near Gympie, Queensland. The tree is a hermaphrodite, pollinated by a wide range of insects including Coleoptera, Diptera, Hemiptera, Hymenoptera and Lepidoptera.

A. cincinnata is highly productive under acid (pH 4-5) and high aluminium soil conditions. The soils are usually red and yellow podzolics, or yellow and red earths derived from sediments, schists, granite and volcanics. It is also found on deep, well-drained siliceous sands, peaty sands, soils associated with seasonal swamps and leached kranozems. The well-drained soils are of low to moderate fertility.

A. cincinnata is adapted to the humid tropics and subtropics. The trees grows best on lowlands and foothills but extends to the somewhat hilly tablelands and can withstand seasonal waterlogging. It is intolerant to frost and drought. Throughout much of its range, this acacia grows with fringing rainforest or as a constituent of rainforest regrowth areas. Confined to the east coast of Queensland in 2 main areas, in northern Queensland from Cairns to Mackay and in the south from Fraser Island to Brisbane. There are isolated occurrences on the lower slopes of the moister coastal ranges, such as the Eungella Range, between the main areas of distribution. In northern Queensland on some sites, A. cincinnata is codominant with A. aulacocarpa, A. mangium, A. polystachya and closed forest trees such as Alstonia muellerana. On other sites, it occurs with Acacia crassicarpa, A. flavescens, Eucalyptus intermedia, E. pellita, E. tereticornis and E. torelliana. In the south of its range, A. cincinnata is a component of open forest or tall open forest of eucalypts including Eucalyptus intermedia, E. microcorys, E. pilularis and E. resinifera. It is also recorded as a shrub occurring in the drier parts of swamps dominated by Melaleuca spp.

During the period of 1982-1995 provenance trials for A. cincinnata were carried out by the Forest Science Institute of Vietnam and growth was found to be poor. Trials have also been established in several other countries: between 1985 and 1995 in Sri Lanka and in March 1984, in the southwest Pacific with very poor growth. Screening trials of the species were also performed in December 1987 to January 1988 by the South Africa Development Coordination Conference (SADCC) jointly with the ICRAF agroforestry project that operates in Tumbi, near Tabora, Tanzania.

Trees are easily propagated from seed. Seeds require pretreatment with concentrated sulphuric acid for 0.5-2 hours, or are immersed into boiling water for 30 seconds, followed by draining and soaking in tap water for 24 hours. Germination rate averages 80%. A nursery phase of 3-4 months is suitable, and the seedlings are transplanted at the 3-leaf stage into containers, or are amenable to direct sowing in the field if weeds are controlled initially. Early growth and crown development are less than for other acacia species, and a greater attention to weed control is necessary for the 1st few years. Superior individual trees of this species have potential for vegetative reproduction.

Saplings may be coppiced at higher cutting heights (about 0.5 m) but show limited regrowth if cut near ground level. Trees are site sensitive, being prone to premature senescence, gummosis and crown thinning if planted off site. The stem form can vary markedly in field trials, from specimens with a straight, tapering bole and small, horizontal branches to a bushy shrub, indicating the importance of species site matching and screening of provenances before embarking on broad-scale plantings. Best performance is achieved on deep, loamy soils and a short dry season. Trees have shown good wind resistance to tropical cyclones and typhoons. Growth rate is moderate in the early years, typically 1.5-2.5 m/year. Height growth and a dbh of 1-2.5 cm/year are recorded in humid parts of Southeast Asia. The most rapid growth has been recorded from an ex-forest site in Sabah, Malaysia, where annual height growth increment was 4.1m/year and dbh increment of 3 cm/year. On favourable sites, the rotation period for sawn timber is expected to be about 25 years.

No serious pests or diseases have been reported.

A. cincinnata is easily propagated from seed, which has an orthodox storage behaviour. There are about 82,000 viable seeds/kg and germination rate is about 80% .

Erosion control: A. cincinnata has been successfully employed to restore land that has been degraded by slash-and-burn agriculture in Laos; also suitable for reforestation on poor soils. Shade or shelter: It is suitable as a shade tree for cardamom and cocoa. Nitrogen fixing: A. cincinnata nodulates and is nitrogen fixing. Boundary or barrier or support: Trees are suitable as supports for passion fruit and yams. Intercropping: It has been grown infrequently as an exotic but appears to have excellent potential for agroforestry purposes when planted on suitable sites, for example in southern China.

Fodder: Young trees resprout well following cutting and have potential for production of animal fodder, if palatability and nutrient levels are satisfactory. Fuel: A dense wood that burns well when dry. Fibre: The wood may be a suitable source of kraft pulp with high screened pulp yield (77%), high pulpwood productivity (308 kg/cubic m) and acceptable bleaching characteristics. It has excellent potential as a source for fibre pulp in papermaking industries. Timber: Wood is dark brown, attractively marked, close-grained, hard, tough, with a basic density of 510-580 kg/cubic m; it is somewhat greasy in nature. It is used for decorative purposes including cabinet work and turnery, and is also suitable for poles and posts. The wood is reportedly resistant to the teredo marine borer and may be useful for some marine purposes.