Key to Acacia

View taxon page for Acacia

(For a list of species in Acacia, use the above link.)

Jepson Manual glossary definitions can be seen by moving your cursor over words underlined with dots.

1. Leaves 2-pinnate

2. 1° leaflets 2–5 pairs ..... A. baileyana

2' 1° leaflets generally > 6 pairs (3–13)

3. Twigs winged; 2° leaflets >= 10 mm ..... [A. decurrens]

3' Twigs angled; 2° leaflets < 7 mm

4. Leaf main axis with raised glands at each 1° 

leaflet 

A leaf-like unit of a compound leaf; distinguished from a leaf by the absence in its axil of a bud, branch, thorn, or flower; lacking lateral, basal appendages (stipules); either simple (leaf 1-compound, with primary leaflets) or compound (leaf 2-compound, with primary and secondary leaflets; 3-compound, with primary, secondary, and tertiary leaflets, etc).

pair; fruit glabrous, silver-blue ..... A. dealbata

4' Leaf main axis with raised glands at most 1° leaflet pairs and generally between; fruit ± hairy, dark brown ..... [A. mearnsii]

1' Leaves 

simple 

Composed of a single part; undivided; unbranched.

5. Leaf < 40 mm

6. Stipular spines present; heads 1 ..... [A. paradoxa]

6' Stipular spines 0; heads in racemes

7. Leaf > 4 mm wide, tip not spine-like ..... [A. podalyriifolia]

7' Leaf <= 1.5 mm wide, tip spine-like ..... [A. verticillata]

5' Leaf generally > 40 mm

8. Leaf with 1 prominent midvein

9. Petiole base 4–8 mm; 

raceme 

In flowering plants excluding Asteraceae, Cyperaceae, Poaceae, and some other groups, an unbranched inflorescence in which the flowers are borne on pedicels and nearly always open from the bottom to the top of the inflorescence. 2. In Asteraceae, Cyperaceae, Poaceae, and some other groups, a raceme-like inflorescence is one in which the inflorescence units (e.g., heads in Asteraceae; spikelets in Cyperaceae and Poaceae), instead of individual flowers, are stalked and attached directly to the main axis of the inflorescence, not to branches, and in which floral development may or may not proceed as in 1.

, occasionally 

panicle 

1. In flowering plants excluding Asteraceae, Cyperaceae, Poaceae, and some other groups, a branched inflorescence in which the basal or lateral flowers (or some of them) open before the terminal or central flowers on any axis. 2. In Asteraceae, Cyperaceae, Poaceae, and some other groups, a panicle-like inflorescence is one in which at least some of the inflorescence units (e.g., heads in Asteraceae; spikelets in Cyperaceae and Poaceae), instead of individual flowers, are attached (stalked or unstalked) to branches and not directly to the main axis of the inflorescence and in which floral development may or may not proceed as in 1.

of 10–30 heads ..... [A. pycnantha]

9' Petiole base <= 4 mm; raceme of 2–9 heads

10. Leaf narrowly 

lanceolate 

Narrowly elongate, widest in the basal half, often tapered to an acute tip.

; 

head 

1. A dense, often spheric inflorescence of sessile or subsessile flowers.
2. In Asteraceae and some other groups, a head-like inflorescence is one in which sessile or subsessile inflorescence units (e.g., heads in Asteraceae, umbels enclosed by involucres in Eriogonum), instead of individual flowers, are attached in a short dense cluster without an evident axis or branches.

5–7 mm wide; gland above 

petiole 

Leaf stalk, connecting leaf blade to stem; sometimes more or less indistinct.

base not obvious, < 1 mm wide ..... [A. retinodes]

10' Leaf 

linear 

Elongate, with nearly parallel sides; narrower than elliptic or oblong.

to narrowly 

elliptic 

In the shape of a flattened circle or ellipse; wider than linear

; head 8–12 mm wide; gland above petiole base obvious, 1–2 mm wide ..... A. saligna

8' Leaf with >= 2 ± prominent longitudinal veins

11. Flowers in spikes ..... A. longifolia

11' Flowers in heads, these 1 or in racemes or 

panicles 

1. In flowering plants excluding Asteraceae, Cyperaceae, Poaceae, and some other groups, a branched inflorescence in which the basal or lateral flowers (or some of them) open before the terminal or central flowers on any axis. 2. In Asteraceae, Cyperaceae, Poaceae, and some other groups, a panicle-like inflorescence is one in which at least some of the inflorescence units (e.g., heads in Asteraceae; spikelets in Cyperaceae and Poaceae), instead of individual flowers, are attached (stalked or unstalked) to branches and not directly to the main axis of the inflorescence and in which floral development may or may not proceed as in 1.

12. Leaves, stems resinous, vanilla-scented when crushed ..... A. redolens

12' Leaves, stems not resinous, not vanilla-scented when crushed

13. Shrub, branches dense, 

spreading 

Oriented more or less perpendicularly to the axis of attachment; often, more or less horizontal.

from base; 

leaf 

Organ arising from a stem, generally composed of a stalk (petiole) and a flat, expanded, green, photosynthetic area (blade); distinguished from a leaflet by the presence in its axil of a bud, branch, thorn, or flower; sometimes with lateral, basal appendages (stipules); either simple (toothed, lobed, or dissected but not divided into leaflets) or compound (divided into leaflets).

narrowly 

oblong 

Longer than wide, with nearly parallel sides; wider than linear.

to obovate, generally 4–15 mm wide ..... A. cyclops

13' Tree, generally with 1 trunk; leaf (except juvenile) lanceolate to oblanceolate, generally 6–30 mm wide ..... A. melanoxylon

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