Natural populations

Acacia leucoclada has two subspecies [1,2,3]:

Subsp. leucoclada is endemic to New South Wales extending from near Warialda in the north of the State, south along the western slopes of the Great Dividing Range to Wagga Wagga region and extends west to the Pilliga Scrub area. Sapling regrowth derived from root suckering often surrounds mature trees.
Subsp. argentifolia is a tree up to 10m tall and has a separate occurrence further north, extending from near Kingaroy in southeastern Queensland to the Koreelah region in northern New South Wales.

Acacia leucoclada grows on hilly undulating terrain or along creek banks and prefers gravelly, sandy clay loams and sandy loams [1,2,3].

Flowering and seeds

Flowers occur during July to September; mature pods are present during November to January [1,2,3,4,5]. There are about 50 viable seeds per gram [5]. Nicking or boiling the seeds in water for a minute at 100°C is required to induce germination. The seeds start to germinate in 4-5 days if grown at 25°C [5].

Cultivation and uses

Acacia leucoclada is a moderate to fast growing, frost tolerant species, with potential as a windbreak and for gully erosion control [2,3]. Provenance variation in A. leucoclada is poorly known but differences in performance of the two subspecies may be likely. The wood of this species has potential for posts, poles or rails, firewood or charcoal and pulpwood [1,2,3]. Some trees have the potential to form dense root suckering clumps which could be favourable attribute to remediate sites that have severe gully erosion but on other sites could pose a problem.

Key descriptors subsp. leucoclada:
Climate parameters
Mean annual rainfall: 500-850 mm
Rainfall distribution: pattern summer or uniform
Mean annual temperature: 8-23 °C
Mean max. temperature of the hottest month: 28-34 °C
Mean min. temperature of the coldest month: 0-3 °C
Frosts per year: up to 20
Frost intensity: light to moderate (0 to -5°C)
Altitude: 200-800 metres
Tolerance of climate extremes
Drought: known to be moderately drought tolerant
Fire: killed by damaging fire does not regenerate foliage
Frost: tolerates frosts in the 0° to -5°C range or tolerates heavy frosts colder than -5°C
Soil factors
Texture: clay loam, heavy clay (greater than 50% clay), light to medium clay (35-50% clay) or loam, sandy loam, sandy clay loam
Soil pH reaction: acidic (less than 6.5) or 2. neutral (6.5-7.5)
Soil depth: moderate to deep (30-100 cm or greater)
Drainage: well-drained
Salinity: non-saline
Tolerance of adverse soils
Extremes in pH: acidity
Salinity: nil - sensitive to saline soils
Soil waterlogging tolerance: nil - sensitive to waterlogged soils
Biological traits under cultivation
Habit: evergreen shrub or tree 5-10 m tall
Longevity: moderate to long lived (>15 years) or short-lived less than 15 years
Growth rate: moderate to fast
Coppicing ability: nil or negligible
Root system: moderate to deep, shallow and spreading, fixes nitrogen via root symbiot, forms root suckers
Erosion control potential: excellent for clayey sites or excellent for sandy sites
Shade tolerance: grows best in full sunlight
Wood density: low (less than 600 kg/cubic metre) or mod. to high (greater than 600 kg/cubic metre)
Carbon sequestration potential: moderate to high
Uses
Potential farm use: excellent windbreak, good for fence posts, good ornamental attributes or shelterbelt or shade for stock
Wood products: light construction or posts (including fencing)
Potentially undesirable attributes
Fire sensitivity: killed by severe fires (seeder)
Growth habit: mod. to strong propensity to root sucker or shallow roots may outcompete adjacent plants
Weediness: high potential based on its biology

Key descriptors subsp. argentifolia:
Climate parameters
Mean annual rainfall: 500-950 mm
Rainfall distribution pattern: summer
Mean annual temperature 8-24 °C
Mean max. temperature of the hottest month 26-32 °C
Mean min. temperature of the coldest month 0-4 °C
Frosts per year: up to 20
Frost intensity: light to moderate (0 to -5°C)
Altitude: 200-1000 metres
Tolerance of climate extremes
Drought: known to be moderately drought tolerant
Fire: killed by damaging fire does not regenerate foliage
Frost: tolerates frosts in the 0° to -5°C range or tolerates heavy frosts colder than -5°C
Soil factors
Texture: clay loam, heavy clay (greater than 50% clay), light to medium clay (35-50% clay) or loam, sandy loam, sandy clay loam
Soil pH reaction: acidic (less than 6.5) or 2. neutral (6.5-7.5)
Soil depth: moderate to deep (30-100 cm or greater)
Drainage: well-drained
Salinity: non-saline
Tolerance of adverse soils
Extremes in pH: acidity
Salinity: nil - sensitive to saline soils
Soil waterlogging tolerance: nil - sensitive to waterlogged soils
Biological traits under cultivation
Habit: evergreen tree 5-10 m tall
Longevity: moderate to long lived (>15 years)
Coppicing ability: nil or negligible
Root system: moderate to deep, shallow and spreading, fixes nitrogen via root symbiot, forms root suckers(?)
Erosion control potential: excellent for clayey sites or excellent for sandy sites
Shade tolerance: grows best in full sunlight
Wood density: low (less than 600 kg/cubic metre) or mod. to high (greater than 600 kg/cubic metre)
Carbon sequestration potential: moderate to high
Uses
Potential farm use: excellent windbreak, good for fence posts, good ornamental attributes, shelterbelt or shade for stock
Specialty products: pollen has value for apiculture, foliage, fruits have potential for floriculture
Urban use: good as an ornamental or amenity plant or suitable as a screen or hedge
Wood products: pulpwood (wood chips for paper pulp), light construction or posts (including fencing), wood composites, medium density fibreboard, oriented strand board, plywood
Potentially undesirable attributes
Fire sensitivity: killed by severe fires (seeder)
Growth habit: shallow roots may outcompete adjacent plants
Weediness: high potential based on its biology

References

[1] Boland DJ, Brooker MIH, Chippendale GM, Hall N, Hyland BPM, Johnson RD, Kleinig DA, McDonald MW, Turner JD (2006) Forest Trees of Australia. CSIRO Publishing, Collingwood.

[2] Doran JC, Turnbull JW (eds.) (1997) Australian Trees and Shrubs: species for land rehabilitation and farm planting in the tropics. Australian Centre for International Agricultural Research, Canberra [ACIAR books online: http://www.aciar.gov.au/publication/MN024].

[3] Maslin BR and McDonald MW (2004) AcaciaSearch-evaluation of Acacia as a woody crop option for southern Australia. Rural Industries Research Development Corporation Publication No. 03/017, Canberra.

[4] Cunningham GM, Mulham WE, Milthorpe PL, Leigh JH (1992) Plants of Western New South Wales, Inkata Press, Port Melbourne, Victoria.

[5] Gunn BV (2001) Australian Tree Seed Centre Operations Manual. Internal Publication, CSIRO Australian Tree Seed Centre, ACT. [Online at http://www.ensisjv.com/Portals/0/atsc-opmanualcomplete.pdf Accessed March 2008]

Internet links

Charles Sturt University's Virtual Herbarium: http://www.csu.edu.au/herbarium/acacleuc_sws.html

PlantNET National Herbarium of New South Wales: http://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Acacia~leucoclada

World Wide Wattle: http://www.worldwidewattle.com/speciesgallery/species-intro.php?id=23896; and http://www.worldwidewattle.com/infogallery/utilisation/acaciasearch/pdf/leucoclada.pdf

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