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Mt Ainslie, ACT

Munghorn Gap, NSW

seedling

in flower

Natural populations

Acacia implexa is a widespread species in eastern Australia, extending from an outlier on the Atherton Tableland in north Queensland, south through southeastern Queensland and along the coast and tablelands of eastern New South Wales. It is widespread in Victoria and an outlier occurs on King Island, Tasmania. This species is a small to medium sized tree up to 15 m tall with a dbh up to 50 cm. It grows on a wide range of different sites and is commonly found on shallow, well-drained soils.

Flowering and seeds

Flowering in this species usually occurs during December to March, but may occur at other times of the year depending on seasonal conditions [1,2]. Seeds mature about 11 months later just prior to the next flowering event [2]. There are about 40 viable seeds per gram [2,3]. Nicking or boiling the seeds in water for a minute at 100°C is required to promote germination. The seeds start to germinate in about 5 days if grown at 25°C [3].

Cultivation and uses

Acacia implexa is a fast growing, nitrogen fixing tree that can be grown on a range of recharge sites [1,2]. Although best development will be on deeper soils, rocky, shallow soils could be targeted. From limited plantings to date it appears that this species exhibits considerable provenance variation, particularly for frost tolerance. Its wood has potential as craftwood and for speciality furniture timber, being similar in appearance to Blackwood (A. melanoxylon ), and its bark has a high tannin content [1,2]. This species is considered to be slightly salt tolerant [5].

Key descriptors:
Climate parameters
Mean annual rainfall: 500-2000 mm
Rainfall distribution pattern: summer, uniform or winter
Mean annual temperature: 9-22 °C
Mean max. temperature of the hottest month: 21-34 °C
Mean min. temperature of the coldest month: -2-10 °C
Frosts: frost free or more or less frost free, up to 20 or greater than 20
Frost intensity:  light to moderate (0 to -5°C) or heavy (greater than -5°C)
Altitude: 3-1320 metres
Tolerance of climate extremes
Drought: known to be moderately drought tolerant
Fire: regenerates foliage after damaging fire
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), loam, sandy loam, sandy clay loam or sand
Soil pH reaction: acidic (less than 6.5) or neutral (6.5-7.5)
Soil depth: skeletal to shallow (less than 30 cm)
Drainage: well-drained
Salinity: non-saline
Tolerance of adverse soils
Extremes in pH: acidity
Extremes in texture: clayey or sand
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 or tree 10-20 m tall, usually produces a clear trunk
Longevity: moderate to long lived (>15 years) or short-lived less than 15 years
Growth rate: fast
Coppicing ability: vigorous, responds to pruning, pollarding
Erosion control potential: excellent for clayey sites or excellent for sandy sites
Root system: moderate to deep, shallow and spreading, fixes nitrogen via root symbiot
Wood density: mod. to high (greater than 600 kg/cubic metre)
Carbon sequestration potential: moderate
Uses
Specialty products: pollen has value in apiculture, high tannin content in bark
Traditional Aboriginal uses: fish poison, implements/artefacts, medicinal, seeds/fruits eaten
Wood products: craftwood (for turnery etc.), flooring (including parquetry), high quality fuelwood, light construction, panelling, speciality timber for quality furniture
Potentially undesirable attributes
Growth habit: mod. to strong propensity to root sucker or shallow roots may outcompete adjacent plants
Weediness: high potential based on its biology

References

[1] 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.

[2] Boxshall B, Jenkyn T (2001) Lightwood, Acacia implexa, Farm Forestry Species Profile for North Central Victoria, Department of Primary Industries, Victoria (DPI).

[3] 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]

[4] Marcar NE, Crawford DF (2004) Trees for Saline Landscapes. RIRDC Publication Number 03/108, Canberra.

Internet links

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

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

World Wide Wattle: http://www.worldwidewattle.com/infogallery/utilisation/acaciasearch/pdf/implexa.pdf

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