Leaves alternate or opposite, simple or compound, lamina with oil dots that are usually aromatic when crushed; stipules usually absent but gland-like stipules present in some species of Eriostemon and Philotheca.
Inflorescences terminal or axillary, sometimes ramiflorous, umbellate or cymose clusters of 1–many flowers. Flowers actinomorphic and mostly bisexual, commonly 4- or 5-merous. Sepals usually 4 or 5, ± fused at the base or united in a cup. Petals mostly 4 or 5, imbricate or valvate, usually free but fused in most species of Correa. Stamens either same number as the petals or twice as many or rarely more numerous; filaments free or cohering in bundles; anthers 2-locular and often apiculate; dehiscence introrse or lateral by longitudinal slits. Nectariferous disk mostly present. Gynoecium superior, carpels usually 4 or 5, 1-locular carpels; carpels either fused completely or free and ± coherent towards their bases and united above by their simple styles; styles free or fused; ovules 2–several per loculus.
Fruit various, often of 1–5 cocci (sometimes called follicles) which usually dehisce along their inner and apical edge, occasionally a berry, drupe, capsule or 1–5 samaras; seeds sometimes winged.
This family is important for a large number of ornamental and food plants. Many varieties of Citrus are extensively cultivated including oranges, lemons, grapefruit, mandarins, tangarines and limes. Many natives are cultivated as ornamentals, particularly species of Boronia, Crowea, Eriostemon, Phebalium and Correa. Timber is obtained from a number of the rainforest species, such as Halfordia and Flindersia. The fruit of Citrus australis and C. australasica are used for making jam.
Taxa not yet included in identification key
Coatesia,
Microcybe
| | Key to the genera | |
| 1 | Leaves all 1-foliolate or simple. | 2 |
| At least some leaves pinnate, 2- or 3-foliolate, or bipinnate. | 19 |
| 2 | Branches of young plants bearing solitary or paired spines in the leaf axils; fruit a berry containing juice sacs. | Citrus |
| Branches never bearing axillary spines; fruit dehiscent or drupaceous.
Back to 1 | 3 |
| 3 | Flowers 4-merous, petals and sepals 4. | 4 |
| Flowers usually 5-merous and petals and sepals 5, rarely flowers 6-merous.
Back to 2 | 9 |
| 4 | Leaves alternate (P. virgata). | Philotheca |
| Leaves opposite.
Back to 3 | 5 |
| 5 | Petals united into a tubular or campanulate corolla, sometimes separating as the flower expands. | Correa |
| Petals free.
Back to 4 | 6 |
| 6 | Fruit a drupe; ovary with carpels fused into a unit; stamens divergent. | 7 |
| Fruit composed of 1–4 basally fused, dehiscent cocci; ovary with carpels ± free; stamens pyramidally arranged and incurved over the ovary.
Back to 5 | 8 |
| 7 | Flowers unisexual; petals persistent in fruit; stigma (in functionally female flowers) broadly 4-lobed. | Sarcomelicope |
| Flowers bisexual; petals not persistent in fruit, rarely semi-persistent; stigma scarcely differentiated from the style.
Back to 6 | Acronychia |
| 8 | Styles terminal or subterminal; leaves usually <8 cm long and <1 cm wide; petals <2 cm long, pink, mauve, white, or bluish; shrubs in open communities. | Boronia |
| Styles inserted above the middle of each carpel, but not terminal; leaves 8–15 cm long and >1.5 cm wide; petals c. 1.5–2 cm long, creamish; rainforest tree.
Back to 6 | Medicosma |
| 9 | Leaves opposite or nearly so. | 10 |
| Leaves alternate.
Back to 3 | 11 |
| 10 | Fruit a 5-valved, 5-locular capsule; seeds winged; buds naked; fertile stamens 5 (opposite the sepals) with alternate stamens reduced to staminodes. | Flindersia |
| Fruit composed of 1–5 dehiscent cocci; seeds not winged; buds with scales completely enclosing the leaf and floral primordia; fertile stamens 10.
Back to 9 | Bosistoa |
| 11 | Stamens 5; seeds blue-black, shining, held in dehiscent cocci by the persistent funiculus. | Geijera |
| Stamens 10; seeds either held in a drupaceous fruit or released from dehiscent cocci.
Back to 9 | 12 |
| 12 | Ovary with carpels fused into a unit; carpels united at maturity; fruit a drupe; rainforest trees. | Halfordia |
| Ovary with carpels ± free; carpels ± separate at maturity; fruit consisting of 1–5 basally fused, dehiscent cocci; shrubs or occasionally small trees, rarely in rainforest.
Back to 11 | 13 |
| 13 | Calyx minute, hidden among hairs and inconspicuous; petals valvate in bud, stellate-tomentose outside. | Asterolasia |
| Calyx conspicuous, or if small then petals imbricate in bud.
Back to 12 | 14 |
| 14 | Petals c. 5-veined from base and densely stellate-scaly outside; leaves 3-veined from base; peduncle with several prominent, rounded imbricate bracts. | Eriostemon |
| Petals 1-veined at base, glabrous, simple or stellate hairy or scaly outside; leaves 1-veined from base; peduncle without prominent bracts, or if present basal.
Back to 13 | 15 |
| 15 | Plants stellate-scaly, especially on young growth. | 16 |
| Plants glabrous or with simple or stellate hairs.
Back to 14 | 17 |
| 16 | Anthers basifixed, apex with a prominent spherical gland; bracteoles basal to pedicel and insignificant. | Phebalium |
| Anthers versatile, without an apical gland; bracteoles medial or supra-medial on pedicel.
Back to 15 | Nematolepis |
| 17 | Anthers with a sterile white apiculum (sometimes minute), stamens usually pyramidally arranged and incurved over the ovary. | 18 |
| Anthers without a sterile apiculum, although occasionally with a terminal gland, stamens divergent.
Back to 15 | Leionema |
| 18 | Anther and apiculum glabrous. | Philotheca |
| Anther and apiculum pilose.
Back to 17 | Crowea |
| 19 | Leaves pinnate with the leaflets alternately arranged on the rachis; fruit an indehiscent berry. | 20 |
| Leaves 2- or 3-foliolate to pinnate, or bipinnate with lateral leaflets in opposite pairs on the rachis; fruit either dehiscent or indehiscent (drupe, samara or individual carpels).
Back to 1 | 21 |
| 20 | Petals <5 mm long, valvate in bud; ovary loculi not twisted; cotyledons thin, folded. | Micromelum |
| Petals >8 mm long, imbricate in bud; ovary loculi twisted; cotyledons thick, not folded.
Back to 19 | Murraya |
| 21 | Rachis of leaves and stems prickly. | Zanthoxylum |
| Rachis of leaves and stems not prickly.
Back to 19 | 22 |
| 22 | Flowers 4-merous with 4 petals and 4 sepals. | 23 |
| Flowers usually 5-merous, with 5 petals and 5 sepals.
Back to 21 | 29 |
| 23 | Fruit an indehiscent drupe, with or without septicidal fissures; ovary with carpels fused into a unit. | Acronychia |
| Fruit of 2–4 ± free follicles or cocci, dehiscent or rarely indehiscent; ovary with carpels ± free.
Back to 22 | 24 |
| 24 | Stamens 4. | 25 |
| Stamens 8.
Back to 23 | 26 |
| 25 | Seeds black and shining, held in dehiscent cocci by the persistent funiculus; rainforest trees with leaflets 2.5–20 cm long. | Melicope |
| Seeds dull or shiny, ejected from dehiscent cocci; shrubs or small tree chiefly in sclerophyll forest and heath, leaflets 0.2–10 cm long.
Back to 24 | Zieria |
| 26 | Ovules 6–8 per carpel; cocci transversely ridged, 6–10 mm long. | Bouchardatia |
| Ovules 2 per carpel; cocci not transversely ridged, usually <6 mm long.
Back to 24 | 27 |
| 27 | Individual carpels indehiscent in fruit; leaflets usually 8–22 cm long (A. octandra). | Acronychia |
| Individual carpels dehiscent in fruit; leaflets usually 0.2–10 cm long.
Back to 26 | 28 |
| 28 | Fruit subfleshy, orange to red; leaves usually 3-foliolate and leaflets 2.5–10 cm long; tree of dry rainforest, restricted to the headwaters of the Clarence and Richmond Rivers (NC). | Dinosperma |
| Fruit not fleshy, brown to blackish; leaves 3–11-foliolate or rarely bipinnate, leaflets 0.2–6 cm long; shrubs of heath, woodland and sclerophyll forests; however, if either leaflets >2.5 cm long or plants growing in rainforest, then not in the NC north of Grafton.
Back to 27 | Boronia |
| 29 | Fruit a 5-valved, 5-locular capsule or a schizocarp-capsule; fertile stamens 5 (opposite the sepals), alternate stamens reduced to staminodes. | Flindersia |
| Fruit either an indehiscent samara or composed of 1–5 dehiscent cocci; fertile stamens 10.
Back to 22 | 30 |
| 30 | Leaves alternate; fruit an indehiscent samara, surrounded by a broad, flat, membranous wing when mature. | Pentaceras |
| Leaves opposite; fruit dehiscent; mature cocci not surrounded by a membranous wing.
Back to 29 | 31 |
| 31 | Ovules 2 per carpel; buds naked; each carpel with a prominent upper abaxial gland. | Acradenia |
| Ovules 4–6 per carpel; buds with scales completely enclosing the leaf and floral primordia; carpel glands absent.
Back to 30 | Bosistoa |
