Flowers appearing axillary (however, a foliose inflorescence) or organised into a terminal botryoid or paniculate inflorescence, subtended by modified leaves (often reduced to scale-like bracts); prophylls (also have been referred to as bracteoles) 2, inserted near middle of pedicel to just below calyx. Calyx 2-lipped. Corolla 2-lipped, zygomorphic (approaching actinomorphic in some species), mauve to purple-blue, white; or red, yellow, or green; sometimes accompanied by stripes or markings in throat, tube or lower corolla lobe; tube usually expanded in throat; lower lip usually spreading but strongly reflexed in some species, 3-lobed; upper lip erect or extended forward in some species, emarginate or 2-lobed. Stamens mostly 4 fertile (two species have 2 fertile and 2 staminodes); anthers 2-locular, introrse, with connective often elongated into an appendage. Ovary 4-lobed; style terminal (not gynobasic) but inserted between ovary lobes; stigma 2-fid.
Fruiting calyx often enlarged and frequently conspicuously coloured. Mericarps usually 4, ± obovoid.
This genus is currently under revision and several species complexes are unresolved. Major work is required on complexes associated with P. denticulata, P. incana, P. lasianthos, and P. saxicola. Natural hybrids are suspected to occur between several species and most species appear to be capable of hybridizing when in cultivation. The current key to Prostanthera incorporates modifications from several publications and new discoveries in NSW over the last decade that have been applied to the original key by Barry J. Conn and Trevor C. Wilson (2015) Two new species of Prostanthera (Lamiaceae) in New South Wales. Telopea 18: 463-474.
| | Key to the species | |
| 1 | Calyx lobes unequal in length; corolla mauve to white, with tube short, broad apically; lower lobe longer and more spreading than the erect upper lobes; fruit enclosed by inward folded lower calyx lobe; upper calyx lobe usually recurved | 2 |
| Calyx lobes ± equal in length; corolla red to pink, or bluish to yellowish green (never mauve to white) with tube long, slightly expanded apically; median upper and lower lobes ± equal; fruit not enclosed by the calyx lobes | 73 |
| 2 | Flowers arranged in bracteose inflorescences (appearing terminal), the floral leaves all or mostly reduced to membranous, usually caducous prophylls | 3 |
| Flowers arranged in leafy botryoids (appearing axillary), with subtending leaves (of flowers) similar to and sometimes smaller than the leaves on the branchlets
Back to 1 | 38 |
| 3 | Leaves with margin entire (although may appear toothed because of tubercules on the margin) | 4 |
| Leaves with margin variously toothed
Back to 2 | 20 |
| 4 | Branches glabrous, except for at nodes or within the groove between ridges | 5 |
| Branches sparsely to densely hairy
Back to 3 | 7 |
| 5 | Leaves 40–70 mm long, 12–26 mm wide, aromatic | Prostanthera petraea |
| Leaves 15–45 mm long, 4–8(-12) mm wide, non-aromatic (or very faintly aromatic)
Back to 4 | 6 |
| 6 | Erect shrub 1–3 m high, leaves < 3.5 mm wide, corolla mauve without markings, anther connective extended into an appendage as long as the anther | Prostanthera linearis |
| Erect subshrub, 0.3–1 m high, leaves > 3.5 mm wide, corolla white to mauve with markings in throat, anther connective without extension (lacking anther appendage)
Back to 5 | Prostanthera hindii |
| 7 | Anther appendages as long as anther locule | 8 |
| Anther appendages absent or less than half the anther locule length
Back to 4 | 10 |
| 8 | Branchlets rounded and evenly covered by long antrorse hairs, upper leaf surface hairy, adaxial lobe of mature fruiting calyx deltoid in shape | Prostanthera lithospermoides |
| Branchlets 4-ridged with short hairs restricted to within grooves, upper leaf surface glabrous, adaxial lobe of mature fruiting calyx ovate
Back to 7 | 9 |
| 9 | Leaf lamina >8 mm wide, length to width ratio <2; leaf margin usually with widely spaced, shallow teeth; flowers clustered in racemiform conflorescences; calyx glabrous | Prostanthera prunelloides |
| Leaf lamina <7 mm wide, length to width ratio >2; leaf margin entire; flowers clustered in dense head-like bracteose botryoidal conflorescences; calyx hairy
Back to 8 | Prostanthera conniana |
| 10 | Leaves with lamina very broadly ovate or almost circular | 11 |
| Leaves with lamina ovate or narrowly ovate
Back to 7 | 12 |
| 11 | Leaves grey-green; lamina very broadly ovate, base truncate; prophylls reduced, soon caducous (in flower); anthers separated during anthesis | Prostanthera cruciflora |
| Leaves dark to light green; lamina almost circular, base cuneate; prophylls conspicuous and persistent; anthers held in pairs within corolla tube
Back to 10 | Prostanthera rotundifolia |
| 12 | Leaf margins flat, leaves glabrous | 13 |
| Leaf margins recurved, leaves hairy
Back to 10 | 16 |
| 13 | Calyx densely hairy; leaves with lamina narrowly ovate | Prostanthera discolor |
| Calyx glabrous or almost so; leaves with lamina ovate
Back to 12 | 14 |
| 14 | Largest Leaves at least 2.5 cm long | Prostanthera ovalifolia |
| Largest leaves less than 2.5 cm long
Back to 13 | 15 |
| 15 | Indumentum consisting of short, curled hairs | Prostanthera cineolifera |
| Indumentum consisting of short, straight hairs
Back to 14 | Prostanthera lanceolata |
| 16 | Leaves 5–10 mm wide | 17 |
| Leaves 1.5–6 mm wide
Back to 12 | 18 |
| 17 | Leaves shorter than 14 mm long | Prostanthera stricta |
| Leaves greater than 14 mm long
Back to 16 | Prostanthera makinsonii |
| 18 | Adaxial leaf surface hairy and without tooth-like hairs and tubercules | Prostanthera hirtula |
| Adaxial leaf surface with only tooth-like hairs often associated with tubercules
Back to 16 | 19 |
| 19 | Branch indumentum with patent or spreading hairs and regularly distributed sessile glands,pherophylls hastate, glandular hairs present at least on calyx | Prostanthera crocodyloides |
| Branch indumentum with geniculate antrorse hairs and sessile glands occasional to absent,pherophylls ovate, glandular hairs absent on reproductive material
Back to 18 | Prostanthera denticulata |
| 20 | Leaves flat | 21 |
| Leaves with margin recurved or revolute
Back to 3 | 36 |
| 21 | Leaves deeply toothed with teeth rounded and directed forward; branches and leaves moderately to densely covered with distinct, long (1–1.5 mm long), ± spreading hairs | Prostanthera askania |
| Leaves shortly toothed; branches and/or leaves glabrous or if hairy then hairs short (less than 1 mm long) and curled
Back to 20 | 22 |
| 22 | Flowers white, or with pale wash of mauve, spots in throat of corolla, inside and outside of corolla hairy, anther appendage at least as long as anther locule | 23 |
| Flowers deep mauve, corolla markings absent, inside corolla not hairy, anther appendage shorter than locule or absent
Back to 21 | 31 |
| 23 | Leaf lamina ovate to ± circular, apex obtuse to rounded | Prostanthera prunelloides |
| Leaf lamina narrowly ovate, narrowly elliptic (sometimes ovate); apex obtuse, tapering or acute
Back to 22 | 24 |
| 24 | Leaf margin with few teeth (<5 teeth) or margin entire (teeth absent) | 25 |
| Leaf margin with 5 or more teeth
Back to 23 | 26 |
| 25 | Small tree, up to 7 m high; lamina 11–16 mm wide; pedicel (2–) 4–7 mm long; abaxial median lobe of corolla c. 4.5 mm long, 4–4.5 mm wide; inflorescences 4–8-flowered | Prostanthera largiflorens |
| Shrub 1–2 m high; lamina very narrowly ovate to very narrowly elliptic,37–52(–64) mm long, 5.5–10 mm wide, with margin entire; pedicel 2–2.5 mm long; abaxial median lobe of corolla 11–11.5 mm long, c. 12 mm wide; inflorescences 15–20-flowered
Back to 24 | Prostanthera williamsii |
| 26 | Inflorescence at least 30-flowered (rarely up to 40-flowered in P. lasiangustata, but then leaves narrow, 6–18 mm wide | 27 |
| Inflorescence up to 20-flowered
Back to 24 | 28 |
| 27 | Mostly small to medium-sized trees, 5–8 m high, sometimes an openly branched shrub up to 4 m high; leaf size highly variable; lamina 27.5–89(–123) mm long, 9.5–25(–29) mm wide; base cuneate, sometimes slightly oblique; margin usually slightly recurved, irregularly toothed (6–30 teeth per side); pedicel 0.4–2 mm long, glabrous, moderately to densely glandular (widespread throughout NSW, Vic. and Tas.) | Prostanthera lasianthos |
| Spreading shrub up to 4 m high, up to 3 m in diameter; lamina 26–36.5 mm long, 6–9.5 mm wide; base tapering to almost cuneate; margin slightly recurved, shallowly toothed (5 or 6 teeth per side, rarely to 8), pedicel 1–1.5 mm long; sparsely hairy to almost glabrous, or sometimes moderately hairy, moderately glandular (Known only from Central Tablelands, NSW)
Back to 26 | Prostanthera lasiangustata |
| 28 | Lamina narrow, up to 9.5 mm wide | 29 |
| Lamina 9.5–24 mm wide
Back to 26 | 30 |
| 29 | Lamina narrow, 6–9.5 mm wide, shallowly toothed, with 5 or 6 (or 8) teeth per side; podium 1–1.5 mm long | Prostanthera lasiangustata |
| Lamina narrow, 4–5 mm wide, distantly toothed, with 16–20 teeth per side; podium 2.5–3 mm long
Back to 28 | Prostanthera tallowa |
| 30 | Leaf venation distinct; calyx tube (1.4–)1.8–2.5 mm long; abaxial lobe of corolla 6–6.5 mm long (adaxial lobe 3.5–4.5 mm long); shrubs 1.5–2 m high | Prostanthera subalpina |
| Leaf venation faint; calyx tube 2.6–3 mm long; abaxial lobe of corolla 8–9.5 mm long (adaxial lobe 4–6 mm long); shrubs 2–3 m high
Back to 28 | Prostanthera rupicola |
| 31 | Leaves with lamina broadly ovate, obovate or almost circular, base cuneate | 32 |
| Leaves with lamina ovate to narrowly ovate
Back to 22 | 33 |
| 32 | Leaves with lamina broad-ovate to obovate or ± circular, apex rounded, margins entire or irregularly lobed or crenate | Prostanthera rotundifolia |
| Leaves with lamina ovate, apex obtuse, margins ± finely and regularly toothed, often slightly irregular
Back to 31 | Prostanthera melissifolia |
| 33 | Leaves with usually 3 teeth on each side of margin, older branches sometimes inserted at 90 degree angle | Prostanthera incisa |
| Leaves entire or with teeth, older branches inserted at less than 90 degree angle
Back to 31 | 34 |
| 34 | Calyx densely hairy; leaves with lamina narrowly ovate to oblong | Prostanthera discolor |
| Calyx glabrous or almost so; leaves with lamina ovate
Back to 33 | 35 |
| 35 | Branchlets hairy or with hairs at least restricted to decussate grooves | Prostanthera ovalifolia |
| Branchlets glabrous
Back to 34 | Prostanthera caerulea |
| 36 | Leaves glabrous, except for a few short stiff hairs near margin leaf margins | Prostanthera denticulata |
| Leaves hairy on both surfaces, margins crenate
Back to 20 | 37 |
| 37 | Leaves c. 5(–7) mm long, with short, stiff hairs | Prostanthera violacea |
| Leaves (8–) c. 10 mm long, finely and densely hairy
Back to 36 | Prostanthera incana |
| 38 | Leaves convex or with margin recurved to revolute | 39 |
| Leaves flat or margin conduplicate or incurved
Back to 2 | 60 |
| 39 | Leaves ± terete, oblong, linear, or deeply 3- or 5-fid (in Prostanthera staurophylla) with lobes linear | 40 |
| Leaves narrowly ovate to broadly ovate, ± circular or obovate, never lobed
Back to 38 | 47 |
| 40 | Prophylls at least as long as the calyx tube | Prostanthera floydii |
| Prophylls shorter than the calyx tube
Back to 39 | 41 |
| 41 | Leaves ± terete; margin entire or deeply 3- or 5-fid and lobes 3–5 mm long; prophylls not persistent, c. 0.5 mm long; branches densely covered with shortly curled hairs | 42 |
| Leaves oblong, narrowly oblong or linear; margin entire; prophylls persistent, at least 1.6 mm long; branches glabrous between nodes or sparsely to densely covered with ± straight, spreading to appressed hairs
Back to 40 | 43 |
| 42 | Adult leaves grey-green, strongly revolute such that lamina appears subterete, 5–16 mm long; margin entire or deeply 2- or 3-fid, densely covered with sessile glands; branches densely covered with sessile glands; anther appendage absent or minute | Prostanthera teretifolia |
| Adult leaves lime- to dark green, oblong or linear, if lobed, then lobes linear, never terete-like, 2–9 mm long, deeply (2–)3(–7)-fid, with scattered glandular hairs adaxially; branches densely covered with podiate glandular hairs; anther appendage present
Back to 41 | Prostanthera staurophylla |
| 43 | Branches 4-ridged (often winged), glabrous, except for nodes | 44 |
| Branches not 4-ridged, hairy throughout
Back to 41 | 45 |
| 44 | Nodes and bases of short shoot distinctly hairy; flower approximately 4 times longer than pedicel; prophylls opposite; adaxial calyx lobe apiculate and approximately equal in size to abaxial calyx lobe | Prostanthera linearis |
| Nodes with a few short hairs present; pedicels as long as or up to 2 times as long as the flower; prophylls ± subopposite; adaxial calyx lobe rounded, shorter than abaxial calyx lobe
Back to 43 | Prostanthera elisabethae |
| 45 | Leaves with apex acute; calyx lower lip often retuse with two sharp points, calyx glabrous | Prostanthera scutellarioides |
| Leaves with apex obtuse; calyx lower lip rounded and hirsute or with at least a few sparse hairs
Back to 43 | 46 |
| 46 | Leaves evenly covered with short straight hairs and margin shortly (often indistinctly) lobed to bluntly toothed; hairs suberect to spreading, not appressed; anther appendage absent | Prostanthera stenophylla |
| Leaves with only a few hairs or glabrous and with margin entire; hairs appressed, antrorse, short; anther appendage present
Back to 45 | Prostanthera saxicola |
| 47 | Leaves wrinkled with margin crenate | Prostanthera rugosa |
| Leaves ± smooth with margin entire
Back to 39 | 48 |
| 48 | Spines present, weakly erect or prostrate shrubs | Prostanthera sejuncta |
| Spines absent, open erect shrubs
Back to 47 | 49 |
| 49 | Leaves ± circular, usually appearing angular-ovate (rhombic) | Prostanthera rhombea |
| Leaves narrowly ovate to ovate or obovate, if broadly ovate then usually appearing narrowly ovate because margin revolute (in Prostanthera decussata)
Back to 48 | 50 |
| 50 | Leaves glabrous | 51 |
| Leaves hairy, at least with a few short tooth-like hairs near margin
Back to 49 | 52 |
| 51 | Leaves obovate, 4–6.5 mm long; prophylls not persistent, 3–3.5 mm long; strongly aromatic shrub; branches densely covered with short, ± spreading hairs | Prostanthera cuneata |
| Leaves narrowly ovate, 5–15 mm long; prophylls persistent, 2.5 mm long; slightly aromatic; branches sparsely covered with short, appressed hairs between ridges
Back to 50 | Prostanthera phylicifolia |
| 52 | Leaves often with upper surface almost glabrous, having a few tooth-like hairs | 53 |
| Leaves with upper surface moderately to densely hairy
Back to 50 | 57 |
| 53 | Leaves > 22 mm long, without tuberculate hairs, calyx tube > 2.6 mm long | Prostanthera floydii |
| Leaves < 22 mm long, with tuberculate hairs, calyx tube < 2.6 mm long
Back to 52 | 54 |
| 54 | Leaves 8–20 mm long; calyx with glandular hairs | Prostanthera crocodyloides |
| Leaves 4–10 mm long; calyx without glandular hairs
Back to 53 | 55 |
| 55 | Stems densely hairy; leaves hairy on adaxial surface | Prostanthera decussata |
| Stems sparsely to moderately hairy; leaves with adaxial surface glabrous
Back to 54 | 56 |
| 56 | Leaves not clustered in axils; flowers axillary and with dark spots in corolla throat | Prostanthera howelliae |
| Leaves clustered in axils; flowers usually in racemose inflorescences (rarely axillary) and without markings in corolla throat
Back to 55 | Prostanthera denticulata |
| 57 | Anther appendage absent, dark mauve markings in corolla, leaves grey-green, never toothed (if missing spots and not grey-green= P. rhombea) | Prostanthera granitica |
| Anther appendage about as long as locule, lower inside corolla throat white covered with orange markings; leaves green, sometimes toothed
Back to 52 | 58 |
| 58 | Indumentum white, stem hairs spreading to slightly retrorse, prophylls > 0.7 mm wide, corolla white with markings in throat | Prostanthera volucris |
| Indumentum hyaline, stem hairs retrorse, stem and calyx hairs spreading or slightly retrorse, prophylls < 0.7 mm wide, corolla mostly mauve but with markings over a white throat
Back to 57 | 59 |
| 59 | Branchlets, leaves and calyces scabrous hirsute; leaves narrowly ovate to narrowly elliptic, up to 8 mm long; prophylls up to 2.5 mm long | Prostanthera marifolia |
| Branchlets, leaves and calyces densely and softly hairy; leaves broadly ovate, often cordate, 6–13 mm long; prophylls 2–5.5 mm long
Back to 58 | Prostanthera densa |
| 60 | Branchlets, leaves and calyces with glandular hairs | Prostanthera cryptandroides |
| Branchlets, leaves and calyces without glandular hairs
Back to 38 | 61 |
| 61 | Branchlets, leaves and calyces glabrous | Prostanthera striatiflora |
| Branchlets, leaves or calyces hairy
Back to 60 | 62 |
| 62 | Leaves narrowly obovate, elliptic or ovate (i.e. superficially linear) to linear | 63 |
| Leaves ovate, elliptic or obovate, to broadly so
Back to 61 | 65 |
| 63 | Leaves conduplicate or incurved (usually sometimes appearing ± terete) | Prostanthera nivea |
| Leaves ± flat (sometimes slightly channelled above, margin sometimes also slightly incurved or recurved)
Back to 62 | 64 |
| 64 | Erect shrub 1–3 m high; leaf lamina 10–50 mm long, 0.5–2 mm wide; anther appendage 1–1.5 mm long | Prostanthera nivea |
| Low spreading, decumbent or sub-prostrate, or weakly erect subshrub, to 1 m high; leaf lamina 4–10 mm long, 1–4 mm wide; anther appendage 0.8–1 mm long
Back to 63 | Prostanthera junonis |
| 65 | Leaves obovate or spathulate | 66 |
| Leaves narrowly to broadly ovate, sometimes weakly obovate
Back to 62 | 67 |
| 66 | Sprawling subshrub, stem indumentum antrorse appressed, leaf margin flat and 3.5–5 mm wide | Prostanthera palustris |
| Erect to spreading shrub, stem indumentum ± spreading, leaf margin undulate and 2–3 mm wide
Back to 65 | Prostanthera spathulata |
| 67 | Strongly and sometimes unpleasantly aromatic shrub; leaves with margin dentate to deeply dissected | Prostanthera incisa |
| Non-aromatic or aromatic shrub; leaves with margin entire
Back to 65 | 68 |
| 68 | Branches very densely hairy all over, hairs often spreading | 69 |
| Branches glabrous or moderately to sparsely hairy with hairs appressed, and if dense or non-appressed, then localised at either nodes or within the groove between longitudinal ridges
Back to 67 | 70 |
| 69 | Leaves nearly glabrous on both sides, corolla up to 8 mm long and mauve without markings in throat, anther appendage as long as anther | Prostanthera gilesii |
| Leaves densely hairy on both sides, corolla at least 12 mm long and white with markings in throat, anther appendage shorter than anther
Back to 68 | Prostanthera makinsonii |
| 70 | Erect subshrub to shrub, leaves (10-)15–45 mm long | 71 |
| Prostrate to erect subshrub, leaves 3–15 mm long
Back to 68 | 72 |
| 71 | Shrub 1–3 m high, leaves < 3.5 mm wide, corolla mauve without markings, anther connective extended into an appendage as long as the anther | Prostanthera linearis |
| Subshrub 0.3–1 m high, leaves > 3.5 mm wide, corolla white to mauve with markings in throat, anther connective without extension (lacking anther appendage)
Back to 70 | Prostanthera hindii |
| 72 | Prostrate to erect shrub, spreading to compact, 0.2–2 m high; calyx tube tube 2–3.5 mm long; anther appendage 0.5–1.5 mm long | Prostanthera saxicola |
| Low straggling shrub to 1 m high; calyx tube tube 1.5–2 mm long; anther appendage 0.5–0.7 mm long
Back to 70 | Prostanthera junonis |
| 73 | Prophylls inserted at base or on lower half of pedicel | Prostanthera ringens |
| Prophylls inserted at base of calyx or on upper half of pedicel
Back to 1 | 74 |
| 74 | Leaves with lamina ± terete | Prostanthera aspalathoides |
| Leaves with lamina ovate to narrowly ovate, sometimes ± circular, never terete or linear-obovate
Back to 73 | 75 |
| 75 | Branches 4-angular and 4-ridged, ridges fused to base of petiole | Prostanthera porcata |
| Branches ± terete, ridges absent
Back to 74 | 76 |
| 76 | Leaves with lamina less than 5 mm long; petiole absent or to 0.5 mm long; venation not visible | Prostanthera serpyllifolia |
| Leaves with lamina more than 10 mm long; petiole more than 1.5 mm long; venation visible, often faint
Back to 75 | 77 |
| 77 | Prophylls 10–18 mm long; inner surface of calyx lobes hairy; leaves non-aromatic | Prostanthera monticola |
| Prophylls 4–6.5 mm long; inner surface of calyx lobes glabrous; leaves aromatic
Back to 76 | Prostanthera walteri |
