Leaves simple, exstipulate, entire, mostly linear, non-decurrent, usually with strongly revolute margins and a reflexed mucro at tip.
Inflorescence cymose, paniculate or pseudo-spicate. Flowerheads with involucral bracts, oblong to lanceolate or ovate, hyaline to opaque, usually white, sometimes yellow or ochre, rarely red-brown; receptacle scales (paleae) present; florets all bisexual, corolla white to cream to yellow, rarely red; anthers shortly tailed with an appendage; style branches with papillose apices.
Achenes more or less cylindrical, sometimes longitudinally angled or ribbed, contracted abruptly at the apex and base, lacking a neck; pappus a single ring of short barbellate bristles, shed as a ring.
Most species are multistemmed erect shrubs of 1-2 m high, frequently found in the understorey of dry sclerophyll woodland where they may be locally frequent or dominant.
Cassinia furtiva is not represented in the key as there is only one collection: 10 km NW of Warialda NWS. It has sticky resinous exudate on both surfaces. It is close to the species Cassinia acciptrum. Cassinia tenuifolia is not represented in the key as it is the only species of Cassinia growing on Lord Howe Island. Cassinia arcuata probably does not occur in NSW although there is a specimen from the Murray River collected by Ferdinand Mueller with no further information. What we thought was Cassinia arcuata is Cassinia sifton, the Sifton Bush or Chinese shrub.
| | Key to the species | |
| 1 | Flower heads arranged in compound dichasia; inflorescence umbrella shaped, flat topped or slightly domed (broader than high) | 2 |
| Flower heads arranged alternately (more or less) along inflorescence axes: inflorescence sub-conical or pseudo spectate (height approximately equalling width or taller than wide) | 24 |
| 2 | Achenes grey to silvery white, not or scarcely constricted at apex, irregularly 4- or 5-ridged longitudinally, glabrous or with subsessile globular hairs | 3 |
| Achenes brown, purple or black, smooth or longitudinally ribbed, cylindrical and usually constricted at the apex, glabrous or with elongated twin hairs
Back to 1 | 7 |
| 3 | Flowerheads all more or less sessile in very dense flat-topped heads; corollas cream to yellow; pappus often absent or reduced to a few bristles; involucral bracts membraneous like cellophane | Cassinia venusta |
| Flowerheads shortly pedunculate, inflorescence relatively open, corolla white to cream and pappus always present; involucral bracts cartilaginous
Back to 2 | 4 |
| 4 | Florets 3–6 per capitulum | 5 |
| Florets 7–12 per capitulum
Back to 3 | 6 |
| 5 | Outer involucral bracts white, strongly 5-ranked; leaves bright green, terete with tightly revolute margins | Cassinia maritima |
| Outer involucral bracts orchre to yellow brown, weakly 5-ranked; leaves grey-green to blue-green, loosely terete to flattened
Back to 4 | Cassinia monticola |
| 6 | Upper leaf surface glabrous or sparsely and coarsely aculeate; achene 0.9–1.1 mm long | Cassinia hewsoniae |
| Upper leaf surface densely and finely acicular; achene 0.5–0.8 mm long
Back to 4 | Cassinia theresae |
| 7 | Leaves all of equal length, and stiffly spreading at approximately 90 degrees, with few or no lateral shoots developing on the current year shoots until the completion of fruiting; involucral bracts yellow to brown or greenish, mainly hyaline, sometimes opaque white on extreme tips | 8 |
| Leaves on current years stems of variable length, spreading, erect or reflexed, with additional lateral shoots developing concurrently with flowering; involucral bracts white or cream
Back to 2 | 16 |
| 8 | Flowerheads white, cream or greenish; involucral bracts opaque, at least at tip | 9 |
| Flowerheads yellow brown; involucral bracts hyaline (apart from stereome)
Back to 7 | 13 |
| 9 | Flowerheads narrow-cylindrical; florets 2–4 per head; paleae often absent; leaf margins revolute to midrib | 10 |
| Flowerheads broad-cylindrical or globose; florets 5–17 per head; paleae present
Back to 8 | 11 |
| 10 | Young stems densely and finely scabrous with gland-tipped hairs; florets 2 or 3 per head | Cassinia leptocephala |
| Young stems cottony; florets 3 or 4 per head
Back to 9 | Cassinia cunninghamii |
| 11 | Leaves narrow-linear, 10–20 times as long as broad; leaf margins revolute to midrib | 12 |
| Leaves narrow-ovate to broad-linear or oblanceolate, 5 or 6 times as long as broad; leaf margins not or hardly revolute and lamina flat with under surface exposed
Back to 9 | Cassinia denticulata |
| 12 | Achenes with very dense white twin hairs 0.2–0.3 mm long onscuring the dark coloured achene; florets 10–17 per head; flowerhead globose | Cassinia macrocephala |
| Achenes with sparse twin hairs 0.05–0.08 mm long, not obscuring achene; florets 5–8 per head; flower head broad-cylindrical
Back to 11 | Cassinia decipiens |
| 13 | Leaves lanceolate, lamina flat with margins not or hardly revolute; involucral bracts transversely wrinkled near tip | Cassinia compacta |
| Leaves linear; lamina flat but margins becoming revolute on drying and leaves then appearing more or less terete; involucral bracts flat or domed but not noticeably wrinkled
Back to 8 | 14 |
| 14 | Mature leaves densely aculeate above with conical hairs 0.05–0.25 mm long | Cassinia telfordii |
| Mature leaves glabrous above, or if hairs present, very sparse, rounded papillose, up to 0.05 mm long
Back to 13 | 15 |
| 15 | Involucral bracts membraneous; flowerheads 2.5–3.5 mm long; leaf tip acute but not or hardly mucronate | Cassinia straminea |
| Involucral bracts cartilaginous with a very woody stereome at base; flowerheads 3.0–5.0 mm long, with 6 or 7 florets; leaf tip abruptly contracted into a straight mucro
Back to 14 | Cassinia accipitrum |
| 16 | Mature achenes mid-brown, smooth (no ribs); twin hairs usually moderately dense | 20 |
| Mature achenes deep red brown, dark chocolate brown or purple-black, with longitudinal ribs and often a transverse apical rib; twin hairs very sparse to almost absent
Back to 7 | 17 |
| 17 | Leaves about 30–40 times as long as wide, 15–50 mm long; flowerheads mostly 4.5–5.0 mm long | 18 |
| Leaves c. 10–30 times as long as broad, 7–25 mm long; flowerheads mostly 5–6 mm long
Back to 16 | 19 |
| 18 | Flowerheads off-white; leaves 25–50 mm long, slightly rugose but glabrous above; florets 5 or 6 per head | Cassinia copensis |
| Flowerheads pale yellow-brown; leaves 15–30 mm long, glabrous and smooth on upper surface, florets 3 or 4 per head
Back to 17 | Cassinia ochracea |
| 19 | Flowerheads 5.5–6 mm long; mucro well developed on leaf tip, reflexed; florets 5–7 per head | Cassinia heleniae |
| Flowerheads < 5.5 mm long; mucro on leaf tip tiny to almost absent; florets 4 or 5 per head
Back to 17 | Cassinia lepschii |
| 20 | Leaves terete cylindrical | 21 |
| Leaves distinctly flattened
Back to 16 | 22 |
| 21 | Inflorescences dull white (ocassionally pink fading to white); leaf surfaces densely scabrous; understorey shrubs in dry or wet sclerophyll forests or woodland | Cassinia aculeata |
| Inflorescences ochre coloured; upper leaf surfaces minutely papillose; on coastal cliffs and dunes
Back to 20 | Cassinia thinicola |
| 22 | Inflorescence bright to dull white (tips of involucral bracts opaque-white | 23 |
| Inflorescence yellow; tips of involucral bracts opaque-yellow
Back to 20 | Cassinia aureonitens |
| 23 | Leaves with well-developed lateral veins, parallel and close to margins; lower surface of leaf olive green to green, with an indumentum composed entirely of dense subsessile globular hairs | Cassinia trinerva |
| Leaves lacking well developed intermarginal veins; lower surface of leaf with an indumentum composed mainly of long white hairs, with sub-globular hairs beneath , or cottony hairs sometimes sparse and lower surface pale green
Back to 22 | Cassinia longifolia |
| 24 | Inflorescence sub-conical in outline, as wide as high, loose, heads white to greenish, corollas creamy white | 25 |
| Inflorescence linear, elongate, often dropping at the tip, loose to compact; heads usually purplish to brownish to reddish; corolla red to cream
Back to 1 | 29 |
| 25 | Leaves linear, c. 1 mm wide | 26 |
| Leaves lanceolate, ovate or oblong, mostly more than 2 mm wide
Back to 24 | Cassinia subtropica |
| 26 | Involucral bract tips opaque | 27 |
| Involucral bract tips translucent
Back to 25 | 29 |
| 27 | Stems olive or red to brown, and/or with a dense indumentum of woolly hairs, or resinous; heads with 5 or 6 florets | 28 |
| Stems white or pale, with soft woolly hairs; heads with 2–4 florets
Back to 26 | Cassinia laevis |
| 28 | Leaves 2–4 cm long; involucral bracts arranged in 4 to 5 longitudinally ranked rows (at maturity), sometimes ranked | Cassinia quinquefaria |
| Leaves 6–12 mm long; involucral bracts arranged spirally
Back to 27 | Cassinia uncata |
| 29 | Leaves and stems conspicuously grey or white with woolly hairs; known only from high altitudes in the NANDEWAR RANGE | Cassinia theodorii |
| Leaves glabrous and sticky above, stems inconspicuously woolly; widespread and often found to be weedy
Back to 26 | Cassinia sifton |
