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Natural populations

Acacia rubida is widespread on the tablelands of the Great Dividing Range of mainland south-eastern Australia [1,2,3]. Its main area of occurrence is from north east Victoria, such as on the Black Range, north to near Stanthorpe in south-eastern Queensland. Its apparent disjunction between the Armidale-Ebor area and Capertee of New South Wales requires validation. This species is usually a shrub that may attain up to 5 m in height. It grows on hilly terrain across a wide range of soils, including skeletal types at high elevations and alluvial soils associated with watercourses [1,2,3]. 

Flowering and seeds

Flowering in this species usually occurs during late winter to spring, but may occur later depending on seasonal conditions [2,3]. Pods mature during summer and there are about 50 viable seeds per gram [4]. Nicking or boiling the seeds in water for a minute at 100°C is required to induce germination. The seeds start to germinate in about 5 days if grown at 25°C [4].

Cultivation and uses

Acacia rubida is a hardy, cold tolerant, relatively fast growing, nitrogen-fixing shrub. It can tolerate relatively shallow skeletal soils and natural occurrences play a valuable role in catchment protection. It is particularly well suited to skeletal soils on cold, high altitude sites.

Key descriptors:
Climate parameters
Mean annual rainfall: 540-1800 mm
Rainfall distribution pattern uniform or winter
Mean annual temperature: 6-15 °C
Mean max. temperature of the hottest month: 18-30 °C
Mean min. temperature of the coldest month: -4-5 °C
Frosts per year: up to 20 or greater than 20
Frost intensity: light to moderate (0 to -5°C) or heavy (greater than -5°C)
Altitude: 120-1550 metres
Tolerance of climate extremes
Drought: known to be drought sensitive(?) or 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), 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) or moderate to deep (30-100 cm or greater)
Drainage: well-drained
Salinity: non-saline
Tolerance of adverse soils
Extremes in pH: acidity
Extremes in texture: clayey
Salinity: nil - sensitive to saline soils
Soil waterlogging tolerance: nil - sensitive to waterlogged soils
Biological traits under cultivation
Habit: evergreen, multi-stemmed from or near ground level, shrub less than 2 m tall or shrub or small tree less than 5 m tall
Longevity: short-lived less than 15 years
Growth rate: fast or moderate
Coppicing ability: nil or negligible
Root system: shallow and spreading, fixes nitrogen via root symbiot, forms root suckers
Erosion control potential: excellent for clayey sites
Carbon sequestration potential: low
Uses
Specialty products: pollen has value for apiculture
Urban use: good as an ornamental or amenity plant or suitable as a screen or hedge
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

References

[1] Maslin BR (2001) Acacia rubida. Flora of Australia, 11A: 400-01.

[2] Costermans LF (1983) Native trees and shrubs of south-east Australia. Rigby.

[3] Tame T (1992) Acacias of New South Wales. Kangaroo Press, Sydney.

[4] 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/acacrubi_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~rubida

World Wide Wattle: http://www.worldwidewattle.com/speciesgallery/species-intro.php?id=23817

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