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 (Karri Wattle)
                5. Whole leaf axis divided into 8-10 pairs of branches each further divided into small
                        leaflets. Flower heads cylindric 30-60 mm long.........................................................Paraserianthes lophantha (Albizia)
            4. Leaflets 10-60 mm long, narrowly egg shaped and often curved, 3-13 mm wide.
                    Inflorescence a large spray of many flower heads.........................................................*A. elata (Mountain Cedar Wattle)
        3. Leaflets 0.4-1 mm wide.
            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 (Mearns Black Wattle)
            6. Leaflets 5-15 mm long, adult leaflets hairless or with a few marginal hairs. Flowers
                    golden yellow. Pods flat, hairless and only slightly constricted between seeds..............*A. decurrens (Early Black Wattle)
    2. Foliage silvery or blue-grey at least when young.
        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 (Cootamundra Wattle)
        7. Whole leaf axis (1)4-12 cm long and with 6-30 pairs of branches.
                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 (Sydney Golden Wattle)
        9. Flower heads globular, 5-7 mm across, the each flower with 5 sepals and 5 petals.
            10. Tree with fissured bark. Phyllodes usually curved. Inflorescence of 3-5 cream flower heads per axil...*A. melanoxylon (Blackwood)
            10. Shrub, rarely a tree with smooth bark. Phyllodes usually straight.
                    Inflorescence of 2 golden yellow heads per axil...............................................................A. cyclops (Red-eyed Wattle)
    8. Phyllodes with only 1 prominent longitudinal vein (midrib).
        11. Spines present, 2 at base of each phyllode. Inflorescence reduced to only 1 flower head per axil..*A paradoxa (Kangaroo Thorn)
        11. Spines absent. Inflorescence with 2-20 flower heads.
            12. Foliage silvery, phyllodes quite broad. Branchlets and also usually the phyllodes hairy…*A. podalyriifolia (Queensland Silver Wattle)
            12. Foliage not silvery. Branchlets and phyllodes hairless.
                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 (Myrtle Wattle)
                13. Branchlets and young shoots not red. Phyllodes often pendulous. Flower heads with many
                        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 (Flinders Ranges Wattle)
                    14. Phyllodes 4-35 mm wide, usually curved. Flower heads golden yellow without conspicuous bracts.
                        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 (Golden Wreath Wattle)
                        15. Phyllodes with blunt tip, leaf stalk 5-8 mm long. Flower heads 6-20 per spray,
                            each head on a thick stalk 3-6 mm long……………………………………………….*A. pycnantha (Golden Wattle)
* = Introduced species in WA.
Courtesy J. Wheeler, Southern Weeds.

Acknowledgments:

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