A key for weedy Acacias and similar native species
1. Adult leaves bipinnate (divided into small segments).
 2. Foliage green to dark green (lower surface sometimes paler).
  3. Leaflets 1.5-13 mm wide.
   4. Leaflets 3-10 mm long, oblong, straight and 1.5-3 mm wide. Inflorescence short or simple, of few flower heads.
    5. Whole leaf axis divided into 2-7 pairs of branches each further divided into small
     leaflets. Flower heads globular, 6-8 mm across....................................................................................A. pentadenia 
    5. Whole leaf axis divided into 8-10 pairs of branches each further divided into small (Karri Wattle)
     leaflets. Flower heads cylindric 30-60 mm long.........................................................................Paraserianthes lophantha
   4. Leaflets 10-60 mm long, narrowly egg shaped and often curved, 3-13 mm wide.  (Albizia)
    Inflorescence a large spray of many flower heads.....................................................................................*A. elata
  3. Leaflets 0.4-1 mm wide.      (Mountain Cedar Wattle)
   6. Leaflets 1-4 mm long, adult leaflets hairless on upper surface and densely hairy on lower surface. Flowers
    pale yellow to cream. Pods circular in cross section, hairy and deeply constricted between seeds..........*A. mearnsii
   6. Leaflets 5-15 mm long, adult leaflets hairless or with a few marginal hairs. Flowers (Mearns Black Wattle)
    golden yellow. Pods flat, hairless and only slightly constricted between seeds.........................................*A. decurrens
 2.Foliage silvery or blue-grey at least when young.   (Early Black Wattle)
  7. Whole leaf axis 1-2.5(3) cm long and with 2-6 pairs of branches. Leaflets hairless,
   5-8 mm long and 0.7-1.6 mm wide.................................................................................................................* A. baileyana
  7. Whole leaf axis (1)4-12 cm long and with 6-30 pairs of branches.(Cootamundra Wattle)
   Leaflets 1.5-6 mm long and 0.4-1 mm wide, with hairs on the lower or both surfaces.................................*A. dealbata
                  (Silver Wattle)
1. Adult 'leaves' (phyllodes) undivided.
 8. Phyllodes with 2-5 prominent longitudinal veins.
  9. Flower heads cylindric, 20-50 mm long, each flower with 4 sepals and 4 petals............................................*A. longifolia
  9. Flower heads globular, 5-7 mm across, the each flower with 5 sepals and 5 petals.(Sydney Golden Wattle)
   10. Tree with fissured bark. Phyllodes usually curved. Inflorescence of 3-5 cream flower heads per axil.....*A. melanoxylon
   10. Shrub, rarely a tree with smooth bark. Phyllodes usually straight.  (Blackwood) 
    Inflorescence of 2 golden yellow heads per axil........................................................................................A. cyclops
 8. Phyllodes with only 1 prominent longitudinal vein (midrib). (Red-eyed Wattle)
  11. Spines present, 2 at base of each phyllode. Inflorescence reduced to only 1 flower head per axil..............*A paradoxa
  11. Spines absent. Inflorescence with 2-20 flower heads. (Kangaroo Thorn)
   12. Foliage silvery, phyllodes quite broad. Branchlets and also usually the phyllodes hairy..........................*A. podalyriifolia
 12. Foliage not silvery. Branchlets and phyllodes hairless. (Queensland Silver Wattle)
  13. Branchlets and young shoots reddish. Phyllodes not pendulous. Flower heads with few
   flowers (2-5 per head), each flower with only 4 sepals and 4 petals..............................................................A. myrtifolia
  13. Branchlets and young shoots not red. Phyllodes often pendulous. Flower heads with many  (Myrtle Wattle)
   flowers (12-80 per head), flowers each with 5 sepals and 5 petals.
   14. Phyllodes narrow, 3.5-8 mm wide, not curved. Flower heads enclosed by conspicuous bracts
    when young. Flowers pale to lemon yellow................................................................................................*A. iteaphylla
   14. Phyllodes 4-35 mm wide, usually curved. Flower heads golden yellow without conspicuous bracts. (Flinders Ranges Wattle)
    15. Phyllodes tipped by sharp point, leaf stalk 1-3 mm long. Flower heads 2-10 per spray,
     each head on a slender stalk 5-15 mm long.........................................................................................A. saligna
    15. Phyllodes with blunt tip, leaf stalk 5-8 mm long. Flower heads 6-20 per spray, each head on a (Golden Wreath Wattle)
                 thick stalk 3-6 mm long.....................*A. pycnantha
                  (Golden Wattle)
                  * = Introduced species
Courtesy J. Wheeler, Southern Weeds.

Acknowledgments:

Collated by HerbiGuide. Phone 08 98444064 or www.herbiguide.com.au for more information.