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.
Australian Wattles at least, can be broadly placed into 1 of 3 recognisable groups:
This wattle belongs to Group 1.
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.
Very small staminate 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; pale-yellow in colour.
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.
Prune after flowering to encourage a denser habit. Check with local native nurseries for availability.
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 will die in a fire and regenerate from seed. Some species exhibit suckering from basal parts and roots.
Acacia is a highly diverse genus, with over 1500 recognised species (placing it in the top-10 most-diverse plant genera) occurring in most continents except for Europe. Australia has about 970 spp., most of which are endemic. There are also about 10 exotic species. NSW has about 235 recognised species. Some species have become weeds in other states outside of their natural range (e.g., wattles from Western Australia into NSW and vice versa).
Acacia – from Greek Akakia – which refers to an Ancient Greek preparation made from one of the many species; the name of which derives from akis, meaning “thorn” – referring to the thorns of species in Africa.
undulifolia – Latin – in reference to the undulating (wavy and not flat) phyllodes, which is particularly noticeable on new growth.
This species is not known to be at risk of extinction in the wild.
Wattle – Acacias of Australia – Acacia undulifolia profile page https://apps.lucidcentral.org/wattle/text/entities/acacia_undulifolia.htm
NSW Flora Online (PlantNET) – Acacia undulifolia profile page https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=wattle&lvl=sp&name=Acacia~undulifolia
Acacia undulifolia profile page https://en.wikipedia.org/wiki/Acacia_undulifolia