This is a straggly shrub to 3 m high with pendulous branches.
It is naturally found in NSW in a scattered distribution over the upper Blue Mountains: from the north, near Mount Monundilla; to the south around the Megalong Valley; as far west as the Cox River; extending to the east as far as the Watagan Range and Bucketty.
It usually grows in gravelly sandy loam soils that have originated from sandstone.
The phyllodes (modified leaves) are green to grey-green or blue-green and slightly asymmetric and flat or sometimes convex or broadly elliptic in shape. They have undulate (wavy) margins. The phyllodes are to 25 mm long and to 16 mm wide.
Flowers are produced between October and November, in solitary globular heads, with each head containing up to 30 flowers. The heads are about 8 mm diameter, hence each flower is very small.
The sub-glossy to blackish seed pods have an oblong shape and are quite straight with a length to 80 mm and about 25 mm wide.
A hardy garden plant and recommended for its long flowering period, it grows best in a sunny, reasonably well drained position in most soils.
Acacias can suffer from a number of pests, including borers, scale, galls and leaf miners. Growing plants suitable to your local environment minimises these occurring.
Propagation is easy from scarified seed by covering with boiling water for 24 hours and discarding any seeds still floating on the surface.
It may be confused with Acacia piligera which has larger yellow flower heads.
Most wattles regenerate from seed after fire.
Acacia – from Greek acis, a thorn.
undulifolia – is in reference to the undulating (wavy and not flat) phyllodes, which is particularly noticeable on new growth.
Not known to be at risk in the wild.