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Genus Prostanthera Family Lamiaceae
Common Name: Mint Bushes

Description: Shrubs or undershrubs, rarely trees; branches subterete to laterally ridged.

Leaves opposite [or rarely in 3-leaved whorls].

Flowers axillary or in terminal botryoid or paniculate inflorescences; bracteoles 2, inserted near middle of pedicel to just below calyx. Calyx 2-lipped. Corolla 2-lipped, purple-blue to white (section Prostanthera), or ± red, sometimes metallic blue-red, rarely yellowish (section Klanderia); tube usually expanded in throat; lower lip usually spreading (particularly section Prostanthera), 3-lobed; upper lip erect or extended forward (section Klanderia), emarginate or 2-lobed. Stamens 4; 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 ± obovoid.


Photo © ANBG

Herbarium
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Herbarium
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Distribution and occurrence: World: c. 100 species, endemic Australia. Australia: all States.

This genus is currently under revision, and several species complexes are unresolved. Natural hybrids occur between several species and most species appear to be capable of hybridizing when in cultivation. Key from: Barry J. Conn and Trevor C. Wilson (2015) Two new species of Prostanthera (Lamiaceae) in New South Wales. Telopea 18: 463-474. The NSW material of Prostanthera melissifolia, typically a Victorian species, either represents a disjunct population, or it is a distinct taxon from the Victorian material and is not included in the key.

Text by B. J. Conn (1993); updated Louisa Murray (January 2016)
Taxon concept:

Taxa not yet included in identification key
Prostanthera melissifolia

 Key to the species 
1Calyx 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 recurved2
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 lobes53
2Flowers arranged in bracteose inflorescences (appearing terminal), the floral leaves all or mostly reduced to membranous, usually caducous prophylls3
Flowers arranged in leafy botryoids (appearing axillary), with subtending leaves (of flowers) similar to and sometimes smaller than the leaves on the branchlets
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26
3Leaves with margin entire4
Leaves with margin variously toothed
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16
4Branches glabrous, except for nodes and/or lateral ridges5
Branches sparsely to densely hairy
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6
5Branches with hairs restricted to nodes; leaves narrowly ovate to linear, usually less than 40 mm long, less than 5 mm wide, petiole absent or up to 2 mm longProstanthera linearis
Branches with hairs restricted to lateral ridges and nodes; leaves ovate, 40–70 mm long, 12–26 mm wide, petiole 5–12 mm long
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Prostanthera petraea
6Anther appendages as long as anther locule7
Anther appendages absent or less than half the anther locule length
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8
7Leaf lamina >8 mm wide, length to width ratio <2; leaf margin usually with widely spaced, shallow teeth; flowers clustered in racemiform conflorescences; calyx glabrousProstanthera 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
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Prostanthera conniana
8Leaves with lamina very broadly ovate or almost circular9
Leaves with lamina ovate or narrowly ovate
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10
9Leaves grey-green; lamina very broadly ovate, base truncate; prophylls reduced, soon caducous (in flower); anthers separated during anthesisProstanthera cruciflora
Leaves dark to light green; lamina almost circular, base cuneate; prophylls conspicuous and persistent; anthers held in pairs within corolla tube
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Prostanthera rotundifolia
10Leaf margins flat, leaves glabrous11
Leaf margins recurved, leaves hairy
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14
11Calyx densely hairy; leaves with lamina narrowly ovateProstanthera discolor
Calyx glabrous or almost so; leaves with lamina ovate
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12
12Largest Leaves at least 2.5 cm longProstanthera ovalifolia
Largest leaves less than 2.5 cm long
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13
13Indumentum consisting of short, curled hairsProstanthera cineolifera
Indumentum consisting of short, straight hairs
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Prostanthera lanceolata
14Leaves 8–13 mm long, ovate but appearing rhombic when margins become excessively recurved after dryingProstanthera stricta
Leaves 10–30 mm long, narrow ovate to ovate, but never ovate when shorter than 15 mm long
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15
15Leaves 1.5–6 mm wide, margins often strongly revoluteProstanthera hirtula
Leaves 6–10 mm wide, margins weakly recurved
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Prostanthera makinsonii
16Leaves flat17
Leaves with margin recurved or revolute
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24
17Leaves deeply toothed with teeth rounded and directed forward; branches and leaves moderately to densely covered with distinct, long (1–1.5 mm long), ± spreading hairsProstanthera askania
Leaves shortly toothed; branches and/or leaves glabrous or if hairy then hairs short (less than 1 mm long) and curled
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18
18Flowers 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 locule19
Flowers deep mauve, corolla markings absent, inside corolla not hairy, anther appendage shorter than locule or absent
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20
19Petiole 4–8 mm long, lamina width 20–30 mmProstanthera lasianthos
Petiole 2–5 mm long, lamina width 4–5 mm
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Prostanthera tallowa
20Leaves with lamina almost circular, base cuneateProstanthera rotundifolia
Leaves with lamina ovate to narrowly ovate
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21
21Leaves with usually 3 teeth on each side of margin, older branches sometimes inserted at 90 degree angleProstanthera incisa
Leaves entire or with teeth, older branches inserted at less than 90 degree angle
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22
22Calyx densely hairy; leaves with lamina narrowly ovate to oblongProstanthera discolor
Calyx glabrous or almost so; leaves with lamina ovate
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23
23Branchlets hairy or with hairs at least restricted to decussate groovesProstanthera ovalifolia
Branchlets glabrous
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Prostanthera caerulea
24Leaves glabrous, except for a few short stiff hairs near margin leaf marginsProstanthera denticulata
Leaves hairy on both surfaces, margins crenate
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25
25Leaves c. 5(–7) mm long, with short, stiff hairsProstanthera violacea
Leaves (8–) c. 10 mm long, finely and densely hairy
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Prostanthera incana
26Leaves convex or with margin recurved to revolute27
Leaves flat or margin conduplicate or incurved
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43
27Leaves ± terete, oblong, linear, or deeply 3- or 5-fid (in Prostanthera staurophylla) with lobes linear28
Leaves narrowly ovate to broadly ovate, ± circular or obovate, never lobed
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34
28Leaves ± 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 hairs29
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
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30
29Adult 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 minuteProstanthera 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
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Prostanthera staurophylla
30Branches 4-ridged (often winged), glabrous, except for nodes31
Branches not 4-ridged, hairy throughout
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32
31Nodes 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 lobeProstanthera 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
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Prostanthera elisabethae
32Leaves with apex acute; calyx lower lip often retuse with two sharp points, calyx glabrousProstanthera scutellarioides
Leaves with apex obtuse; calyx lower lip rounded and hirsute or with at least a few sparse hairs
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33
33Leaves evenly covered with short straight hairs and margin shortly (often indistinctly) lobed to bluntly toothed; hairs suberect to spreading, not appressed; anther appendage absentProstanthera stenophylla
Leaves with only a few hairs or glabrous and with margin entire; hairs appressed, antrorse, short; anther appendage present
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Prostanthera saxicola
34Leaves wrinkled with margin crenateProstanthera rugosa
Leaves ± smooth with margin entire
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35
35Spines present, weakly erect or prostrate shrubsProstanthera sejuncta
Spines absent, open erect shrubs
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36
36Leaves ± 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)
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36
37Leaves glabrous38
Leaves hairy, at least with a few short tooth-like hairs near margin
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39
38Leaves obovate, 4–6.5 mm long; prophylls not persistent, 3–3.5 mm long; strongly aromatic shrub; branches densely covered with short, ± spreading hairsProstanthera 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
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Prostanthera phylicifolia
39Leaves often with upper surface almost glabrous, having a few tooth-like hairs40
Leaves with upper surface moderately to densely hairy
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41
40Leaves hairy, at least with a few short tooth-like hairs near margin; branches densely covered with short to long spreading to antrorse hairs; corolla without markings in throatProstanthera decussata
Leaves with upper surface almost glabrous, having a few tooth-like hairs; branches predominantly glandular, usually sparsely to moderately covered with short, ± antrorse hairs; corolla throat with dark purple spots
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Prostanthera howelliae
41Anther 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
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42
42Branchlets, leaves and calyces scabrous hirsute; leaves narrowly ovate to narrowly elliptic, up to 8 mm long; prophylls up to 2.5 mm longProstanthera marifolia
Branchlets, leaves and calyces densely and softly hairy; leaves broadly ovate, often cordate, 6–13 mm long; prophylls 2–5.5 mm long
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Prostanthera densa
43Branchlets, leaves and calyces with glandular hairsProstanthera cryptandroides
Branchlets, leaves and calyces without glandular hairs
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44
44Branchlets, leaves and calyces glabrousProstanthera striatiflora
Branchlets, leaves or calyces hairy
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45
45Leaves narrowly obovate (often appearing almost linear) or linear, conduplicate or incurved, usually appearing ± terete46
Leaves ± flat or slightly channelled above; margin slightly incurved or slightly recurved
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47
46Erect shrub 1–4 m high; adaxial calyx lobe 3–5 mm long; corolla 14–18 mm long; anther appendage c. 1.5 mm long; leaf lamina 10–50 mm long, 0.5–2 mm wideProstanthera nivea
Low spreading, decumbent or sub-prostrate, or weakly erect subshrub, 0.1–0.3 m high; adaxial calyx lobe 1.5–1.8 mm long; corolla 8–12 mm long; anther appendage 0.5–0.7 mm long; leaf lamina 8–16 mm long, 1–4 mm wide (note: elliptic to narrowly elliptic leaves are also present on young plants or near the base of older plants)
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Prostanthera junonis
47Branchlets moderately to densely hairy, with hairs patent or slightly spreadingProstanthera makinsonii
Branchlets appearing sparsely hairy or with hairs restricted to opposite decussate bands
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48
48Branchlets with opposite decussate bands of hairs (often superficially appearing glabrous)49
Branchlets sparsely hairy with appressed hairs, or if almost glabrous then hairs restricted to nodes
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52
49Leaves obovate to ± spathulate; calyx with inner surface glabrous and outer surface densely hairyProstanthera palustris
Leaves linear, ovate, elliptic, or narrowly obovate; calyx variously hairy or glabrous throughout
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50
50Strongly aromatic shrub; leaves with margin dentate to deeply dissectedProstanthera incisa
Non-aromatic or faintly aromatic shrub; leaves with margin entire
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51
51Erect shrub to 2 m high; calyx with outer surface glabrous or almost so; anther appendages absentProstanthera hindii
Low spreading, decumbent, weak subshrub, erect when young 0.1–0.3 m high; calyx with outer surface sparsely to densely hairy, especially on abaxial surface of tube and abaxial lobe (distinct anther appendages almost as long as the locule)
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Prostanthera junonis
52Leaves (5–)6–10 mm wide, fresh leaves aromatic when crushedProstanthera gilesii
Leaves less than 5 mm wide, not aromatic when crushed
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53
53Leaves up to 15 mm long, branches lacking ridgesProstanthera saxicola
Leaves 15–45 mm long, branches distinctly 4-ridged
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Prostanthera linearis
54Prophylls inserted at base or on lower half of pedicelProstanthera ringens
Prophylls inserted at base of calyx or on upper half of pedicel
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55
55Leaves with lamina ± tereteProstanthera aspalathoides
Leaves with lamina ovate to narrowly ovate, sometimes ± circular, never terete or linear-obovate
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56
56Branches 4-angular and 4-ridged, ridges fused to base of petioleProstanthera porcata
Branches ± terete, ridges absent
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57
57Leaves with lamina less than 5 mm long; petiole absent or to 0.5 mm long; venation not visibleProstanthera serpyllifolia
Leaves with lamina more than 10 mm long; petiole more than 1.5 mm long; venation visible, often faint
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58
58Prophylls 10–18 mm long; inner surface of calyx lobes hairy; leaves non-aromaticProstanthera monticola
Prophylls 4–6.5 mm long; inner surface of calyx lobes glabrous; leaves aromatic
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Prostanthera walteri

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