Plectranthus mandalensis Baker

J. R. Timberlake, E. S. Martins (2013). Flora Zambesiaca, Vol 8: part 8. Royal Botanic Gardens, Kew

Diagnosis

sp. nova, P. mandalense Baker affinis sed folliis ellipticis non late ovatis supra sparsim pubescentibus neque conspicue pubescentibus neque leviter asperis, corolla caerulea haud alba differt. Type: Mozambique, Zambezia, Gurué, Rio Malema, Marope, 22 km from Gurué, de Koning 7530 (LMU holotype, LISC).

Type

Type: Malawi, Mandala, cultivated at Kew, ii.1893, Moir s.n. (K holotype).

Morphology General Habit

Annual or perennial herb 40–60 cm tall; variously reported as aromatic or not

Morphology Stem

Stems erect or ascending, rooting at base, purplish, slightly fleshy with slightly swollen internodes, pubescent with purplish antrorse hairs below and with short spreading glandular hairs on inflorescence axis, with pale sessile glands

Morphology Leaves

Leaves sometimes purplish, ascending, often with young shoots in axils, petiolate; blade 13–90 × 15–70 mm, broadly ovate, crenate, apex acute to obtuse, base attenuate or broadly cuneate, pubescent with conspicuous hairs on upper surface which is rough to the touch, sparsely pubescent beneath, with pale sessile glands; petiole (6)13–60 mm long

Morphology Reproductive morphology Inflorescences

Inflorescence fairly lax with (3)4–6-flowered verticils up to 10–20 mm apart, with bract subtending (1)2–3-flowered sessile cymes; bract 1–2 mm long, elliptic; pedicel 2–4 mm long

Morphology Reproductive morphology Flowers Calyx

Calyx 1.5–2 mm long, pinkish, puberulent, with pale sessile glands; fruiting calyx 5–7 mm long, pedicel attached at ± centre of calyx base; throat oblique; posterior lip obovate, obtuse at apex, curving upwards, shortly decurrent; lateral lobes slightly nearer median lobes of anterior lip, deltoid but with posterior margin slightly extended to form an inconspicuous shoulder, subulate at apex; median lobes lanceolate, longer than lateral-Corolla white, marked pink, 4–5 mm long, puberulent on lobes, with pale sessile glands; tube 3–4 mm long, straight, ± parallel-sided; posterior lip equal to anterior lip; anterior lip 2 mm long, cucullate, finally deflexed

Morphology Reproductive morphology Flowers Androecium Stamens Filaments

Staminal filaments free

Morphology Reproductive morphology Fruits

Nutlets brown with darker, reddish raised areas, 1.5 mm long, broadly ovate, rugulose to ± smooth, producing a small amount of mucilage.

Distribution

Malawi, Mozambique. Known only from Mts Mulanje and Namuli.

Ecology

Evergreen forest floor, forest margins and paths; 1100–2000 m.

Conservation

Reported as VU by Golding (2002). EOO 1271 km2, 19 collections on Mt Mulanje; AOO 507 km2, based on cell width of 7.96 km with 8 cells. Four subpopulations based on adjacent cells; three subpopulations based on Rapoport distance. Decline uncertain as P. mandalensis often grows in open areas of forest; probably Vulnerable D2.

Note

It is reported that flowers often do not open, so cleistogamy may be common.

Recognition

The species is close to Plectranthus guruensis which also has small corollas, but differs in having elliptic leaves and a blue rather than white corolla.