Leaves opposite, alternate or occasionally whorled; laminas simple, usually with entire margins, venation usually pinnate (triplinerved in a few genera), very commonly dotted with conspicuous, translucent oil glands; stipule-like emergences minute or absent.
Inflorescences variable; flowers solitary or in umbel-like or raceme-like inflorescences or from dichasia to many-flowered panicles; sometimes aggregated into conflorescences that are head- or spike-like. Flowers actinomorphic, bisexual, mostly 4- or 5-, rarely 6-merous. Perianth segments usually free but sometimes forming various kinds of calyptra. Sepals usually 4 or 5, often reduced as lobes on edge of hypanthium, often persistent in fruit. Petals as many as calyx lobes, usually free and falling after anthesis, occasionally absent. Stamens usually perigynous, to almost epigynous, 5–numerous, free or grouped into 5 bundles opposite the petals; anthers versatile or adnate. Ovary usually half-inferior (varying from almost inferior to almost superior), 1- to multi-locular; style simple.
| | Key to the genera | |
| 1 | Fruit succulent. | 2 |
| Fruit dry. | 18 |
| 2 | Inflorescences usually terminal and many-flowered; seed relatively large, usually solitary. | 3 |
| Inflorescences axillary, 1 or few-flowered; seed usually small, mostly >1 per fruit, or sometimes only 1.
Back to 1 | 5 |
| 3 | Seeds with a papery testa and separate, green cotyledons. | Syzygium |
| Seeds with no obvious testa, cotyledons fused with a conspicuous dark inclusion spreading through the centre.
Back to 2 | 4 |
| 4 | Fruit apex topped by the persistent, cylindrical, unexpanded free portion of the hypanthium; intercotyledonary inclusion spreading from the base of the fruit. | Waterhousea |
| Fruit apex topped by the circular remnant of the hypanthium rim; intercotyledonary inclusion spreading from the summit of the fruit.
Back to 3 | Acmena |
| 5 | Leaves usually <10 mm wide; flowers solitary in leaf axils; plants of sclerophyll forest, rainforest, heath and scrubland. | 6 |
| Most leaves >10 mm wide; flowers either solitary, clustered or in axillary raceme-like or panicle-like inflorescences; plants of rainforests, sometimes on their margins or in sclerophyll forest.
Back to 2 | 7 |
| 6 | Mature fruit white to greyish or bluish green, often with darker spots; spreading or bushy shrubs to 2 m high; coastal districts and adjacent ranges north from the Sydney district. | Austromyrtus |
| Mature fruit green turning red or black; shrubs or small trees to 12 m high; rare, only on the McPherson and Nightcap Ranges.
Back to 5 | Uromyrtus |
| 7 | Mature fruit yellow, orange or red. | 8 |
| Mature fruit purple or black.
Back to 5 | 13 |
| 8 | Fruit vertically ribbed, bright red. | Eugenia |
| Fruit not vertically ribbed, usually yellow to orange, sometimes red.
Back to 7 | 9 |
| 9 | Sepals and petals mostly 4. | 10 |
| Sepals and petals mostly 5, or occasionally some 4.
Back to 8 | 11 |
| 10 | Leaves 3-veined from base; fruit red turning blackish when mature. | Rhodamnia |
| Leaves not 3-veined from base; fruit yellow to orange.
Back to 9 | Gossia |
| 11 | Mature fruit >2 cm diam.; sepals cohering in the bud, splitting longitudinally at flowering. | Psidium |
| Mature fruit <2 cm diam.; sepals free in the bud.
Back to 9 | 12 |
| 12 | Leaves 1–3 cm wide; ovary 3-locular; mature fruit 5–7 mm diam., topped by erect persistent sepals; petals 4–6 mm long. | Archirhodomyrtus |
| Leaves 2.5–6.5 cm wide; ovary 4-locular , becoming multi-locular by development of false septa; mature fruit 10–15 mm diam. with persistent sepals reflexed; petals 7–10 mm long.
Back to 11 | Rhodomyrtus |
| 13 | Sepals and petals 4. | 14 |
| Sepals and petals 5.
Back to 7 | 15 |
| 14 | Leaves 3-veined from base. | Rhodamnia |
| Leaves not 3-veined from base.
Back to 13 | Lenwebbia |
| 15 | Fruit vertically lobed; ovary 4- or 5-locular. | Decaspermum |
| Fruit not vertically lobed; ovary 2- or 3-locular.
Back to 13 | 16 |
| 16 | Petals 2–5 mm long; testa hard and bony. | 17 |
| Petals 5–7 mm long; testa membranous to papery.
Back to 15 | Pilidiostigma |
| 17 | Anthers with a conspicuous apical appendage; flowers and fruit usually solitary, pendent. | Uromyrtus |
| Anthers topped only by a small apical gland; flowers and fruit occasionally solitary, but usually >1, not pendent.
Back to 16 | Gossia |
| 18 | Flower buds covered with a calyptra formed from the fused perianth segments. | 19 |
| Flower buds not covered with a calyptra.
Back to 1 | 20 |
| 19 | Inflorescences compound, terminal or axillary and anthers versatile and opening by parallel slits and disc steeply depressed in fruit. | Corymbia |
| Inflorescences, anthers and fruit not a combination of the above characters.
Back to 18 | Eucalyptus |
| 20 | Stamens grouped (usually distinctly fused) into 5 bundles opposite the petals | 21 |
| Stamens not in 5 bundles, usually free but occasionally fused into a short tube at the base.
Back to 18 | 24 |
| 21 | Fruit included in the hypanthium or barely exserted; seeds linear. | 22 |
| Fruit exserted from the hypanthium; seeds flat, winged.
Back to 20 | Tristaniopsis |
| 22 | Flowers sessile, aggregated into head- or spike-like conflorescences. | Melaleuca |
| Flowers pedicellate, inflorescences cymose.
Back to 21 | 23 |
| 23 | Leaves opposite and decussate; oil ducts absent from the petioles. | Tristania |
| Leaves alternate along branchlets but clustered in false whorls at the end of the branchlets; oil ducts, containing milky oil, present in the petioles.
Back to 22 | Lophostemon |
| 24 | Leaves opposite. | 25 |
| Leaves alternate.
Back to 20 | 41 |
| 25 | Most leaves >5 mm wide. | 26 |
| Most leaves <5 mm wide.
Back to 24 | 29 |
| 26 | Fruit indehiscent; hypanthium papery to leathery | 27 |
| Fruit a loculicidal capsule; hypanthium woody
Back to 25 | 28 |
| 27 | Leaves with a strong aniseed smell when crushed, margins undulating. | Anetholea |
| Leaves not strongly smelling of when crushed, margins ± flat.
Back to 26 | Backhousia |
| 28 | Flowers sessile, 7 per inflorescence; capsules fused in a woody syncarp. | Syncarpia |
| Flowers pedicellate, numerous; capsules usually ribbed.
Back to 26 | Angophora |
| 29 | Ovary and fruit 2- or 3-locular. | 30 |
| Ovary and fruit 1-locular.
Back to 25 | 38 |
| 30 | Stamens exceeding the petals. | Kunzea |
| Stamens shorter than the petals.
Back to 29 | 31 |
| 31 | Ovary and fruit 2-locular. | Baeckea |
| Ovary and fruit 3-locular.
Back to 30 | 32 |
| 32 | Anthers adnate to filament, dehiscing by pores or short parallel slits. | 33 |
| Anthers versatile, dehiscing by long parallel slits.
Back to 31 | 35 |
| 33 | Inflorescence usually of solitary flowers; bracteoles 2; peduncles generally shorter than pedicels | 34 |
| Inflorescence usually of (2–)3 or more flowers; bracteoles 4–many, clustered at the apex of the peduncle; peduncles generally longer than pedicels
Back to 32 | Sannantha |
| 34 | Sepals ‘compound’, the dorsal lobe often acute; summit of fruit slightly exserted from the fruiting hypanthium; leaves acute to obtuse | Kardomia |
| Sepals simple, obtuse; summit of fruit at or within the rim of the fruiting hypanthium; leaves with a small, recurved mucro
Back to 33 | Harmogia |
| 35 | Ovules and seeds D-shaped, angular. | Baeckea |
| Ovules and seeds ± reniform, not angular.
Back to 32 | 36 |
| 36 | Some stamens opposite centre of petals | 44 |
| No stamens opposite centre of petals.
Back to 35 | 37 |
| 37 | Stamens 5–8; ovules 2 per loculus. | Ochrosperma |
| Stamens 14–18; ovules 8–13 per loculus.
Back to 36 | Triplarina |
| 38 | Stamens 10, twice as many petals, alternating with 10 staminodes; style long-exserted. | 39 |
| Stamens 5–12, up to twice as many as petals, staminodes lacking; style included or very shortly exserted.
Back to 29 | 40 |
| 39 | Sepals terminating in one or more slender processes. | Homoranthus |
| Sepals lacking slender processes, entire or shortly ciliate.
Back to 38 | Darwinia |
| 40 | Stamens <10, usually opposite the sepals; anther connective gland prominent, clavate or ± urceolate. | Thryptomene |
| Stamens 10 or 12 or if 5 then opposite the petals; anther connective gland small, subglobose.
Back to 38 | Micromyrtus |
| 41 | Ovary 1-locular; sepals persistent, membranous, terminating in a long, slender awn. | Calytrix |
| Ovary >1-locular; sepals persistent or not persistent, never ending in an awn.
Back to 24 | 42 |
| 42 | Stamens considerably longer than the petals. | 43 |
| Stamens shorter, or scarcely longer, than the petals.
Back to 41 | Leptospermum |
| 43 | Sepals not persistent, flowers aggregated into spike-like conflorescences. | Callistemon |
| Sepals persistent, flowers in heads or solitary in the leaf axils.
Back to 42 | Kunzea |
| 44 | Shrubs; pedicels shorter than, or as long as, the leaves; bracteoles not persistent. | Rinzia |
| Prostrate plants; pedicels longer than the leaves; bracteoles persistent.
Back to 36 | Euryomyrtus |
