Leaves opposite [or rarely subopposite or whorled], simple or 1-foliolate, palmately 3-foliolate or pinnately 3–19[-41]-foliolate or bipinnate; leaflets with margins entire or toothed, or rarely 3-lobed; lateral leaflets opposite.
Inflorescences axillary or terminal, cymose or paniculate or reduced to single flowers. Flowers bisexual, 4- or rarely 5-merous. Sepals usually 4, free. Petals usually 4, valvate or imbricate, free, persistent or not persistent in fruit. Stamens mostly 8, free, erect or pyramidally arranged. Carpels 4 [or rarely 5], ± free, lacking a sterile apex; styles fused, arising terminally or subterminally from the carpels; stigma scarcely differentiated from style or capitate or grossly swollen and almost sessile; ovules 2 in each carpel.
Fruit of 1–4 cocci; cocci not transversely ridged, with rounded apices; seeds released forcibly from dehiscing cocci, dull or shiny, black.
| | Key to the species | |
| 1 | Hairs stellate; petals valvate, midvein of petal prominently raised on the outer surface. | 3 |
| Hairs simple or absent; petals imbricate (except in B. algida), midvein of petal not prominently raised (except in B. barkeriana). | 2 |
| 2 | Leaves 1-foliolate. | 18 |
| Leaves pinnate with 3 or more leaflets.
Back to 1 | 26 |
| 3 | At least some leaves pinnate with 3–11 leaflets. | 4 |
| All leaves simple or 1-foliolate.
Back to 1 | 13 |
| 4 | Leaflets strongly discolorous, indumentum of the lower surface dense and concealing the epidermis. | 5 |
| Leaflets slightly discolorous or concolourous, indumentum of the lower surface not dense and not concealing the epidermis.
Back to 3 | 7 |
| 5 | Sepals narrow-deltate, at least 2.5 times as long as broad, the apex acute; leaves mostly 3–11-foliolate, rarely some leaves 1-foliolate. | 6 |
| Sepals ovate, 1.5–2 times as long as broad, the apex acute or acuminate; leaves 1-foliolate or 3–7-foliolate.
Back to 4 | Boronia ledifolia |
| 6 | Largest terminal leaflet >20 mm long; largest lateral leaflets >18 mm long; all leaflets 10–15 mm wide; petals 7–8 mm long; coastal ranges north from Coffs Harbour (NC). | Boronia umbellata |
| Largest terminal leaflet <25 mm long, largest lateral leaflets <18 mm long; all leaflets 2–7 mm wide; petals 3–12 mm long; chiefly from Bylong to Denman, W part of the Nandewar Ra. and Gibraltar Ra. N.P. (NT, NWS, CWS)
Back to 5 | Boronia angustisepala |
| 7 | Midrib not raised on the lower surface of the leaflets. | 8 |
| Midrib raised on the lower surface of the leaflets.
Back to 4 | 12 |
| 8 | Sepals narrowly ovate to deltate, at least twice as long as broad. | 9 |
| Sepals ovate to deltate, less than twice as long as broad.
Back to 7 | 10 |
| 9 | Leaves with sparse to moderately dense indumentum; stellate hairs sometimes stalked, grey to white, rays of stellate hairs to 0.5 mm long, flexuous and dull; chiefly on the Western Slopes and adjacent ranges, north from Inverell district (NT, NWS). | Boronia granitica |
| Leaves glabrescent or with a sparse indumentum; stellate hairs not stalked, yellowish; rays of stellate hairs <0.25 mm long, ± straight, shiny; confined to Bolivia Hill (NT).
Back to 8 | Boronia boliviensis |
| 10 | Broadest leaflets >3 mm wide; peduncle 2–10 mm long; leaves sometimes 3-foliolate or 1-foliolate; mature cocci glabrous or hirsute; at Woodsreef (NWS) and from Lees Pinch to Berrima (CC, CT, CWS). | 11 |
| Broadest leaflets <3 mm wide; peduncle <3 mm long; leaves rarely 1- or 3-foliolate and then at first few nodes of branch only; in the Coonabarabran to Warrumbungle Ra. district (NWS).
Back to 8 | Boronia warrumbunglensis |
| 11 | Leaves dorsiventral with lower surface paler than upper surface; from Lees Pinch to Berrima (CC, CT, CWS). | Boronia rubiginosa |
| Leaves isobilateral with lower surface similar colour to upper surface; confined to Woodsreef (NWS).
Back to 10 | Boronia ruppii |
| 12 | Leaves with a moderately dense indumentum; rays of stellate hairs 0.1–1 mm long; | Boronia mollis |
| Leaves glabrous or glabrescent; rays of stellate hairs to 0.25 mm long;
Back to 7 | Boronia fraseri |
| 13 | Leaves sessile. | 14 |
| Leaves petiolate or base so attenuate so as to appear petiolate.
Back to 3 | 16 |
| 14 | Margins of leaves glandular-warty; sepals narrowly ovate to deltate, at least twice as long as broad; rays of stellate hairs usually dull and flexuous. | Boronia repanda |
| Margins of leaves smooth; sepals ovate to deltate, less than twice as long as broad; rays of stellate hairs shiny and usually ± straight.
Back to 13 | 15 |
| 15 | Leaves slightly discolorous, usually glabrescent or rarely with a dense minute indumentum on both surfaces (hirsute Pilliga form); fruit hirsute; Western Slopes (NWS, CWS, NWP). | Boronia glabra |
| Leaves strongly discolorous, upper surface of leaves glabrous and shiny, lower surface with a dense stellate indumentum: fruit glabrous; coastal areas north from Woolgoolga district (NC).
Back to 14 | Boronia rosmarinifolia |
| 16 | Leaves glabrous or glabrescent, only slightly discolorous. | Boronia ruppii |
| Leaves with a dense indumentum (epidermis not visible) on the lower surface (except in some juvenile leaves), adult leaves strongly discolorous.
Back to 13 | 17 |
| 17 | Leaves with upper surface glandular-warty, margins glandular-toothed; leaves papery when dry, not firm. | Boronia chartacea |
| Leaves with upper surface and margins smooth; leaves firm.
Back to 16 | Boronia ledifolia |
| 18 | Leaves broad-obovate to circular. | 19 |
| Leaves narrower, ± linear or terete to elliptic or obovate.
Back to 2 | 20 |
| 19 | Margins of leaves finely toothed; swollen apex of staminal filaments hairy; style vestigial, obscured by the massively swollen globose stigma. | Boronia serrulata |
| Margins of leaves entire; swollen tips of staminal filaments glabrous; style terete; stigma about as wide as style.
Back to 18 | Boronia rhomboidea |
| 20 | Leaves terete to semi-terete. | 21 |
| Leaves ± flat.
Back to 18 | 23 |
| 21 | Staminal filaments glabrous; inflorescences terminal (though often on short axillary shoots). | Boronia deanei |
| Staminal filaments ciliate; inflorescences axillary or axillary and terminal.
Back to 20 | 22 |
| 22 | Leaves 2–8 mm long, obtuse; petals tipped with a small but distinct incurved hook, white to bluish mauve, persistent in fruit. | Boronia coerulescens |
| Leaves 8–25 mm long, acuminate; petals lacking an incurved hook, bright pink, not persistent in fruit.
Back to 21 | Boronia falcifolia |
| 23 | Inflorescences axillary; petals tipped with a small but distinct incurved hook, persistent in fruit; bracts persistent; seeds dull, finely wrinkled. | 24 |
| Inflorescences terminal; petals lacking an incurved hook, not persistent in fruit; bracts not persistent in fruit (often falling before flowering); seeds shiny, smooth.
Back to 20 | 25 |
| 24 | Leaves discolorous, darker on upper surface; branchlets glabrous. | Boronia polygalifolia |
| Leaves concolorous; branchlets with 2 longitudinal pilose lines separated by glabrous decurrent leaf bases.
Back to 23 | Boronia nana |
| 25 | Petals 6–11 mm long; sepals caducous in fruit; bracteoles reduced to minute calli, persistent in fruit. | Boronia barkeriana |
| Petals 3–6 mm long; sepals persistent in fruit; bracteoles scale-like, not persistent in fruit.
Back to 23 | Boronia parviflora |
| 26 | Petals valvate; leaflets spathulate to broad-spathulate, distinctly darker on upper surface; plant ± branching dichotomously around the exclusively terminal inflorescences. | Boronia algida |
| Petals imbricate; leaflets either not spathulate or if so, then concolorous; plant not branching dichotomously; inflorescences axillary or terminal.
Back to 2 | 27 |
| 27 | Petals tipped by a small but distinct incurved hook, usually persistent in fruit; anther appendage white, contrasting with the brown anther connective; seeds dull, finely wrinkled. | 28 |
| Petals lacking a terminal incurved hook, not persistent in fruit; anthers uniformly cream in colour; anther appendage minute or absent; seeds shiny, smooth.
Back to 26 | 31 |
| 28 | Branchlets prominently 4-angled or with 2 deep longitudinal grooves separated by decurrent leaf bases, glabrous; leaves bipinnate. | Boronia anethifolia |
| Branchlets with 2 very shallow pilose longitudinal grooves separated by glabrous to pilose decurrent leaf bases; leaves 3-foliolate to pinnate to bipinnate.
Back to 27 | 29 |
| 29 | Leaflets mostly 3-lobed at apex. | Boronia anemonifolia |
| Leaflets entire.
Back to 28 | 30 |
| 30 | Leaves mostly pinnate to bipinnate; leaflets narrow- to linear-oblong, usually obtuse. | Boronia occidentalis |
| Leaves mostly 3-foliolate; leaflets narrow-elliptic, acute.
Back to 29 | Boronia rigens |
| 31 | Leaves 3-foliolate; leaflets terete. | Boronia falcifolia |
| Leaves pinnate, usually with 5 or more leaflets; leaflets flat to terete.
Back to 27 | 32 |
| 32 | Swollen tip of staminal filaments densely hairy; style vestigial, concealed by the massively swollen, globose stigma. | Boronia floribunda |
| Swollen tip of staminal filaments glabrous; style terete; stigma about as wide as style.
Back to 31 | 33 |
| 33 | Branchlets glandular-warty, usually hairy. | 34 |
| Branchlets not warty, glabrous or sometimes hairy.
Back to 32 | 36 |
| 34 | Leaflets spathulate to broad-spathulate to cuneate; longest leaflets 4–7 mm long. | Boronia microphylla |
| Leaflets mostly narrow-elliptic to oblong; longest leaflets 7–25 mm long.
Back to 33 | 35 |
| 35 | Branchlets glabrous or sparsely hairy between decurrent leaf bases; leaves 45–70 mm long; peduncles 4–15 mm long, pedicels 5–17 mm long. | Boronia muelleri |
| Branches pubescent; leaves 16–26 mm long; peduncles 2–5 mm long, pedicels 5–7 mm long.
Back to 34 | Boronia imlayensis |
| 36 | Branchlets hairy, sometimes the hairs short and restricted to 2 longitudinal lines separated by glabrous decurrent leaf bases. | 37 |
| Branchlets glabrous.
Back to 33 | 38 |
| 37 | Leaflets 0.3–1 mm wide, linear-oblong; sepals and pedicels ± pilose. | Boronia subulifolia |
| Leaflets 1–3 mm wide, mostly narrow-oblong to elliptic; sepals and pedicels glabrous.
Back to 36 | Boronia safrolifera |
| 38 | Margins of leaflets finely glandular-crenulate; leaflets slightly discolorous, darker on upper surface. | Boronia thujona |
| Margins of leaflets entire; leaflets concolorous.
Back to 36 | Boronia pinnata |
