Description: Annual or perennial herbs, shrubs [or trees], variously hairy and conspicuously gland-dotted.
Leaves alternate, mostly 3-foliolate with terminal leaflet largest, sometimes pinnately or palmately 5–11-foliolate [or rarely 1-foliolate]; margins entire or toothed; long-petiolate; stipules 1–11-veined.
Inflorescences of 1-few raceme-like, spike-like or umbelloid in leaf axils; bracts subtending 1–3 flowers, commonly caducous; cupulum absent; peduncle and rachis often elongating after flowering. Flowers cleistogamous (remaining closed and self-pollinating) or chasmogamous (open at pollination); subsessile or pedicellate. Calyx tubular or urceolate-campanulate, teeth ± equal or lower one largest and upper 2 united for most of their length, persistent in fruit. Petals either white and yellow and/or blue to purple. Standard obovate to circular; wing and keel petals adhering above the claw, wings longer than keel. Stamens diadelphous; anthers uniform. Ovary short-stipitate; ovules 1; style gently reflexed; stigma capitate.
Pods reniform-elliptic, indehiscent and adhering to the seed; seed 1, aril absent.
Distribution and occurrence: World: 32 spp., Aust., Malesiana, Asia, Medit., Afr. Aust: 32 spp. (24 spp. endemic), all States.
Species in this genus were previously included in Psoralea. Key based on Grimes (1997).
Text by G.J. Harden & L. Murray
Taxon concept:
| | Key to the species | |
| 1 | At least some leaves with more than 3 leaflets | Cullen tenax |
| Leaves 3-foliolate | 2 |
| 2 | Terminal leaflet more or less sessile and close to the lateral ones; margins of leaflets entire | 3 |
| Terminal leaflets petiolulate and distant from the lateral ones; margins of leaflets toothed
Back to 1 | 4 |
| 3 | Leaflets usually less than 5 mm wide, but always less than 10 mm wide; mostly more than 4 times as long as wide | Cullen tenax |
| Leaflets usually more than 10 mm wide; mostly less than 4 times as long as wide
Back to 2 | Cullen microcephalum |
| 4 | Calyx 2–3 mm long, open in fruit; pod protruding from calyx | Cullen cinereum |
| Calyx 3–10 mm long, not open in fruit; pod enclosed within calyx
Back to 2 | 5 |
| 5 | Small shrubs; stems 0.5–2.5 m high, erect; inflorescences interrupted; plants of heavy soils | Cullen australasicum |
| Herbs; stems usually less than 0.5 m long, usually prostrate or ascending; inflorescences continuous, dense; plants of sandy soils
Back to 4 | 6 |
| 6 | Petals protruding before and after anthesis for at least 1 mm; stems ascending then decumbent | Cullen pallidum |
| Petals enclosed before anthesis and not visible; stems prostrate
Back to 5 | 7 |
| 7 | Calyx silky, visible under long stout spreading hairs, gland-dotted | Cullen graveolens |
| Calyx villous, hidden by dense appressed white hairs; glands on the calyx concealed or lacking
Back to 6 | Cullen patens |
|
