Leaves alternate, terete to lanceolate or oblanceolate, margins entire, apex ± acute, sometimes pungent; ± sessile.
Inflorescences oblong to cylindric spikes; at first terminal then axis usually growing into a leafy shoot. Flowers 5-merous. Hypanthium urceolate to campanulate. Sepals circular. Petals circular, exceeding the sepals. Stamens numerous, exceeding petals, free or rarely shortly united at base; filaments usually glabrous; anthers versatile. Ovary 3- or 4-locular, half-inferior; style with capitate stigma.
Fruit a woody capsule opening loculicidally, 3- or 4-valved, often persistent on stem and enlarging for many years; seeds numerous.
Some species readily hybridize, and as a result it is often difficult to identify these specimens satisfactorily. A number of cultivars are widely grown in gardens, and these are also difficult to assign to a taxon with certainty. Spike dimensions are when flowers are fully open. Fruit dimensions are of mature capsules, after 1–2 years.
| | Key to the species | |
| 1 | Leaves less than 3 mm wide | 2 |
| Leaves more than 3 mm wide | 7 |
| 2 | Leaves less than 4 cm long | 3 |
| Leaves more than 4 cm long
Back to 1 | 6 |
| 3 | Flowers red | 4 |
| Flowers yellow
Back to 2 | 5 |
| 4 | Leaves needle-like, mostly less than 1 mm diam.; spikes 2–3 cm diam.; species of inland plains | Callistemon brachyandrus |
| Leaves flat to subulate, mostly 0.75–3 mm wide; spikes 4–5 cm diam.; species of coastal and tableland districts
Back to 3 | Callistemon subulatus |
| 5 | Branches stiff; leaves 1–2(–3.2) cm long, 0.75–1.5 mm diam.; mainly on the tablelands in boggy heathland | Callistemon pityoides |
| Branches flexuous; leaves 2–5 cm long, 2–5 mm wide; widespread along watercourses, creekbeds and gullies
Back to 3 | Callistemon sieberi |
| 6 | Flowers yellow-green or rarely red; leaves terete or channelled, rough with oil glands | Callistemon pinifolius |
| Flowers red; leaves flat or channelled, not or scarcely rough
Back to 2 | Callistemon linearis |
| 7 | Flowers yellow or green | 8 |
| Flowers red, pink or lilac
Back to 1 | 13 |
| 8 | Fruit less than 5.5 mm diam | 9 |
| Fruit more than 5.5 mm diam
Back to 7 | 12 |
| 9 | Spikes mostly 3–3.5 cm diam., occasionally more | 10 |
| Spikes less than 3 cm diam
Back to 8 | 11 |
| 10 | Bark mostly soft and papery; leaves willow-like, narrowly rhomboidal | Callistemon salignus |
| Bark hard; leaves not willow-like, elliptic to oblanceolate
Back to 9 | Callistemon pallidus |
| 11 | Leaves 6–8 mm wide, broadest below the middle, margins usually recurved; spikes c. 2 cm diam | Callistemon shiressii |
| Leaves 2–5 mm wide, mostly broadest above the middle, margins not recurved; spikes usually 2–2.5 cm diam
Back to 9 | Callistemon sieberi |
| 12 | Leaves grey-green, smooth, apex abruptly narrowed; Wallum heath and hind dunes of northern coastal districts | Callistemon pachyphyllus |
| Leaves dark green, rough with oil glands, apex mostly pointed; tableland species, generally in rocky areas
Back to 8 | Callistemon flavovirens |
| 13 | Flowers red | 14 |
| Flowers purple-pink
Back to 7 | 22 |
| 14 | Stamens fused into a ring at the base | Callistemon viminalis |
| Stamens free
Back to 13 | 15 |
| 15 | Leaves more or less linear | 16 |
| Leaves not linear
Back to 14 | 18 |
| 16 | Spikes less than 5 cm diam., leafy; fruit less than 6 mm diam | Callistemon subulatus |
| Spikes more than 5 cm diam., not leafy; fruit more than 6 mm diam
Back to 15 | 17 |
| 17 | Leaves mostly 8–10 cm long, 5–8 mm wide | Callistemon linearifolius |
| Leaves mostly 5–7 cm long, 3–4 mm wide
Back to 16 | Callistemon rigidus |
| 18 | Leaves willow-like, narrowly rhomboidal, margins undulate | Callistemon acuminatus |
| Leaves generally broadest above the middle, margins not undulate
Back to 15 | 19 |
| 19 | Leaves mostly more than 1 cm wide | Callistemon comboynensis |
| Leaves mostly less than 1 cm wide
Back to 18 | 20 |
| 20 | Leaves with one side almost straight; spikes generally broader than long; fruit 7–8 mm diam | Callistemon montanus |
| Leaves more or less symmetrical; spikes longer than broad; fruit mostly less than 7 mm diam
Back to 19 | 21 |
| 21 | Leaves abruptly narrowed at apex, veins obscure | Callistemon pachyphyllus |
| Leaves not abruptly narrowed at apex, veins evident
Back to 20 | Callistemon citrinus |
| 22 | Leaves more than 5 mm wide | Callistemon citrinus |
| Leaves less than 5 mm wide
Back to 13 | Callistemon pungens |
