The name refers to the branchlets, which when young are flattened and more or less zigzagged and smooth, with green wings along the edges. Older branches lose the wings and are more cylindrical.
The leaves (like most wattles) are actually phyllodes (flattened petioles). They are straight, elliptical, with 5-9 obvious veins running length-ways. There is a small volcano-like gland on the upper edge of the phyllode stalk.

Foliage. Photo: Robert Whyte
Flowers
Aboriginal people used the wood for boomerangs, shields and clubs. The inner bark was stripped away and used for twine. (Queensland Museum).
Sometimes grows in thickets and can regrow from underground after fire, rather than by seed.
Food for Squirrel Gliders and Pale Head Rosellas (gum and seeds).

Foliage. Photo: Robert Whyte
Useful garden plant
Acacia from Greek acis, a thorn, complanata from Latin complano, ‘flattened’, referring to the stems.
Flat-stem wattle often occurs in open forest dominated by scribbly gum (Eucalyptus racemosa) or spotted gum (Corymbia citriodora). More common in bushland between Brisbane and the Sunshine Coast than in other places.
Propagate with scarified seed covered with boiling water and left to sit overnight.
Type specimens were collected by A Cunningham & C Fraser separately in 1829.
A relatively distinctive species with some similarity to A. homoclada, which usually has narrower and more elongated phyllodes.

Foliage. Photo: Robert Whyte