Botanical art
Common names
Creek Wattle
Silver Wattle
Etymology
Acacia rom the Greek 'akakia' and derived rom 'ake' or 'akis' meaning a sharp point or thorn and 'akazo' meaning to sharpen. Dioscorides, the Greek physician and botanist used the word in the 1st century AD or Egyptian thorn tree, Acacia arabica. Rivalis rom the Latin 'rivalis' meaning growing by streams.
Distribution and status
Endemic to South Australia and is confined to northern Flinders Ranges, growing in tall shrubland on ridges and rocky shaly hillsides or along watercourses. Native. Common in South Australia.
Herbarium regions: Lake Eyre, Gairdner-Torrens, Flinders Ranges, Eastern
AVH map: SA distribution map (external link)
Plant description
Small, parachute-shaped trees or shrubs to 4 m high with a dense domed canopy, branching near the ground, or with a single trunk for more or less 1 m before dividing into a number branches. Branchlets reddish and slightly angular. Leaves linear lanceolate to 14 cm long and 5 mm wide; falcate, narrowed towards the base, glabrous and shiny when fresh, with prominent central vein to a short curved apex. Small glands on upper margin at least 15mm above the base. Inflorescences axillary racemes, solitary with small, globular yellow lower-heads. Flowering between May and November. Fruits are smooth, brown, linear pod to 12 cm long and 5 mm wide, straight or curved. Seeds are hard, black, semi-flat, ellipsoid seed to 7 mm long and 4 mm wide. Seed embryo type is investing.
Seed collection and propagation
Collect seeds between November and December. Collect mature pods that are turning brown, with hard, dark seeds inside. Place the pods in a tray and leave to dry or 1-2 weeks or until the pods begin to split. Then rub the dried pods to dislodge the seeds. Use a sieve to separate any unwanted material. Store the seeds with a desiccant such as dried silica beads or dry rice, in an air tight container in a cool and dry place. From one collection, the seed viability was high, at 85%. This species has physical dormancy that needs to be overcome or the seed to germinate (e.g. nicking or softening the seed oat).
| Location | No. of seeds (weight grams) | Number of plants | Date collected | Collection number Collection location | Date stored | % Viability | Storage temperature |
|---|---|---|---|---|---|---|---|
| BGA | 860 (24.96 g) | 200 | 23-Nov-2009 | KHB318 Flinders Ranges | 1-Jun-2010 | 85% | -18°C |
| BGA | 2,750 (49.4 g) | 50+ | 7-Dec-2011 | KHB628 Flinders Ranges | 1-Nov-2012 | 40% | -18°C |
| BGA MSB | 9,500 (281.12 g) 9,500 (281.12 g) | 20+ | 1-Dec-2016 | DJD3598 Flinders Ranges | 1-Nov-2017 | 60% | -18°C |
Number of plants: This is the number of plants from which the seeds were collected.
Collection location: The Herbarium of South Australia's region name.
% Viability: Percentage of filled healthy seeds determined by a cut test or x-ray.