Acacia from the Greek 'akakia' and derived from '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 for the Egyptian thorn tree, Acacia arabica. Merrallii named in honour of Edwin Merrall (1844-1913), a botanical collector in Victoria and Western Australia.
Distribution and status
Found in or near coastal areas in the Nullarbor region, eastwards across Eyre Peninsula, with a small occurrence on Yorke Peninsula; mainly in open scrub vegetation associated with Eucalyptus socialis and E. gracilis, in brown calcareous soils and grey-brown calcareous loams. Also found in Western Australia. Native. Common in South Australia. Common in Western Australia.
Herbarium regions: Nullarbor, Eyre Peninsula, Yorke Peninsula
NRM regions: Alinytjara Wilurara, Eyre Peninsula, Northern and Yorke
AVH map: SA distribution map (external link)
Small, rigid, spreading, procumbent shrubs to 1.5 m high and usually wider than its height. Branches hoary-pubescent slightly angular greyish-brown with grey bark. Phyllodes obliquely ovate-orbicular or obovate to 20 mm long and 15 mm wide; flat, rigid, grey-green, hoary-pubescent when young. Inflorescences simple and axillary, solitary or twin with globular, yellow flower-heads. Flowering between August and October. Fruits are dark brown linear but curved or loosely coiled pod to 60 mm long and 3 mm wide with margins slightly contracted between seeds. Seeds are hard, dark brown to black semi-flat seed to 3 mm long and 2 mm wide with a large fleshy bright-yellow conical aril which is at least half the size of the seed and often broader. Seed embryo type is investing.
Seed collection and propagation
Collect seeds between November and January. Collect mature pods that are turning brown, with hard, dark seeds inside. Place the pods in a tray and leave to dry for 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. This species has physical dormancy that needs to be overcome for the seed to germinate (e.g. nicking or softening the seed coat).