Aeschynanthus are perennial woody based subshrubs, usually epiphytic but sometimes lithophytic in the wild. The stems are branching and the habit varies from stiff and twiggy to pendent and trailing, or creeping and rooting at the nodes. Some species have small-leaved, hairy, creeping juvenile growth and stiff, twiggy, spreading flowering stems.
The leaves are opposite or in a few species whorled, usually thick and leathery, bright to dark green above and much paler sometimes purple-flushed below, with entire or indistinctly toothed margins, the midvein impressed above and prominent below; in most species the other veins are obscure. Leaves of A. longicaulis are beautifully marbled. The leaves may be hairy or, in the majority of species, glabrous, but in those species whose seedling growth has been observed the first few leaves have some hairs regardless of the character of the adult leaves.
Flowers are borne in leaf axils towards or at tips of branches. The calyx is 5-lobed, varying from completely divided to tubular or campanulate, in which case the lobes may be indistinct. It is in a few species asymmetric, and in one species is spathulate. The corolla is tubular and usually arcuate with a somewhat bilabiate limb, the upper 2 lobes being smaller and usually unmarked, the lower 3 lobes often spreading and marked with lines or spots. The 4 stamens are in 2 pairs, the anthers of each pair cohaerent and situated either at the mouth or exserted; the filaments are inserted about halfway down the tube. The staminode is usually tiny. The disc is annular at the base of the stipe, the ovary is terete, grading into the usually hairy style; the stigma is peltate, circular or ovoid. The fruit is a long narrow loculicidally 2-valved capsule containing hundreds of tiny seeds bearing a single hair at one end and one or more at the other.
Aeschynanthus flowers are strongly protandrous (male and female parts mature separately); as the stamens wither and droop the gynoecium rapidly elongates. This, together with corolla shape and copious nectar, indicates pollination by birds in the wild but pollination has not yet been observed. The plants are found in primary and secondary rainforest, often near streams, in conditions of good light but not strong sun and, depending on species, from sea level to 2500m. or more.
Most of the species are horticulturally very attractive. In cultivation they do well in hanging pots or baskets, in a well-drained compost with a high humus content, and with regular feeding. They require good light but not direct sunlight, a minimum temperature of 18°C, and high humidity. Cuttings root readily in perlite or vermiculite, and they set seed fairly readily if hand-pollinated; the capsules can take up to 9 months to mature. Several hybrids have been made, some of which are intersectional, for example A. x splendidus is an old garden hybrid between A. parasiticus (section Diplotrichium) and A. speciosus (section Haplotrichium). It was further crossed with A. longicaulis (also known as A. marmoratus and A. zebrinus, section Polytrichium) to give rise to the cultivar Black Pagoda. Other hybrids include Big Apple, A. fecundus x micranthus, A.sikkimensis x evrardii and A. parvifolius x tricolor. There are some fine cultivars, for example Sumatra Sunburst or Sarasota Sunburst is A. chrysanthus.
Aeschynanthus is comprised of approximately 150 species distributed from the Himalayas east to China, and throughout South-East Asia to the Solomon Islands. The genus is in tribe Trichosporeae in the subfamily Cyrtandroideae, which is characterised by the possession of unequal cotyledons.
Members of the Trichosporeae have seeds with at least one hair or appendage at each end. Aeschynanthus is at present divided into 6 sections, 5 of which are based on the characters of these seed-hairs; however current research indicates that this is in need of revision. Bentham (1876) proposed four sections, Polytrichium, Diplotrichium, Haplotrichium, and Holocalyx (Aeschynanthus); in 1883 Clarke added to Benthams definition of Holocalyx by noting bubble-like cells at the base of one hair, He also recognised another section, Microtrichium, with short broad seed appendages. Schlechter (1923) published a further section, Anisocalyx, for a New Guinea species with a calyx bilabiate for the upper two-thirds, but this is now known to be in section Microtrichium. An additional section, Xanthanthos, was created by Wang (1975) for a single Chinese species.
The seed of many species is not known so their assignment to sections is only tentative; although there is some correlation with other taxonomic characters this is not always reliable and has in the past resulted in some inaccurate placements. In addition the seeds of a few species do not fit easily into any one section; Polytrichium and Diplotrichium appear to be good but the others are less clear-cut. The sections currently used are as follows.
Click here to see an illustration of the seed characteristics of the various sections. This photo of A. evrardii illustrates the hairy/silky nature of the seed mass in many species of Aeschynanthus.
Polytrichium. This small section of about ten species is characterised by the possession of a coma of hairs at the hilar end of the seed and a single hair at the opposite end. The flowers are rather small for the genus, the calyx deeply divided and the corolla rather dull, often greenish or orange-yellow. The habit is spreading and twiggy. The section has a wide geographical range from Burma in the west to New Guinea in the east. Examples in cultivation are A. asclepioides and A. longicaulis.
Diplotrichium. The seeds have two hairs at the hilar end and a single hair at the opposite end. The calyx is partly divided and the corolla red or orange. The habit is bushy and twiggy. This is also a small section and is restricted to India, Burma and Thailand across to SW China. Examples in cultivation are A. parviflorus and A. sikkimensis.
Haplotrichium. This section is characterised by a single long filiform hair at each end of the seed. The calyx is in most cases deeply divided but may be tubular with short lobes and in one species is unlobed. Flower size is very variable and colour is usually orange to red but may be green to deep red. The habit is usually bushy but may be trailing and flexuous. The geographical range is wide, from India eastwards to China, the Philippines and Borneo but it is not yet known from New Guinea; the numerous species placed in this section by Schlechter almost certainly all belong to section Microtrichium. Examples in cultivation are A. hildebrandii and A. micranthus.
Aeschynanthus. Members of this section have seeds with a single long hair at each end, the one at the hilar end having a cluster of bubble-like cells at the base. The calyx is at least partly tubular, or saucer-shaped, and almost always bluntly lobed. Corolla colour is usually red but two species have clear yellow flowers. The habit may be creeping and flexuous or less often twiggy and spreading. The centre of development is in the Malay Peninsula, Sumatra, Java, Borneo, and the Philippines and the section does not extend to India or to New Guinea. Examples in cultivation are A.obconicus, A. parvifolius, A. pulcher, and A. radicans.
Microtrichium. Unlike the filiform seed hairs of the other sections, the appendages on the seeds of members of section Microtrichium are short, broad at the base and tapering to a point. This is the largest and most variable section, displaying calyx form from deeply divided to tubular or spathaceous, corolla colour from greenish to pink, red and purple, and habit from stiff and twiggy to pendulous and flexuous. It extends from the Malay Peninsula to the Solomon Islands, with about 50 species in New Guinea. Examples in cultivation are A. ellipticus, A. longicalyx and A. guttatus.
Xanthanthos. This section, unlike the others, is not based on seed hair characters, but on the yellow or white conspicuously bilabiate corolla with included anthers. As yet the only member is A. denticuliger from China, which is not in cultivation.
Notes are by Mary Mendum, except when indicated as being by Ron Myhr (RM).
Aeschynanthus acuminatus Wallich.
Section Diplotrichium. Distribution: E.
Himalayas, Sikkim to Assam.
Aeschynanthus angustifolius (Bl.) Steud. (A. tetraquetrus C.B. Cl.; A. stenophyllus Ridl.).
Stems pendent, glabrous, purplish; leaves glabrous, short and more or less ovate on the lower parts of the stems, and linear leaves up to 2cm long, often in whorls of 4 or 6, on the upper parts; inflorescence axillary or terminal, single or 2-flowered. Calyx sparsely hairy, up to 4mm; corolla up to 2cm, externally hairy, lime-green or yellowish with purple-edged lobes, internally glabrous, pale yellowish; stamens exserted. Section Haplotrichium. Distribution: Peninsular Malaysia, Java, Sumatra, Moluccas, Sabah, Sarawak.
A. Black Pagoda.
A result of crossing the old intersectional hybrid A. x splendidus (A. parasiticus [Diplotrichium] x speciosus [Haplotrichium]) with A. longicaulis [Polytrichium]. The influence of A. longicaulis may be seen particularly in the beautifully marked leaves.
A. chrysanthus P. Woods.
Stems sprawling, hairy when young; leaves sparsely hairy, up to 9.1 x 3.7cm long, narrowly elliptic to lanceolate, apex acuminate; inflorescence axillary or terminal, 2--6- flowered; calyx deep yellow, glabrous, up to 8.2cm long; corolla up to 9.5cm long, externally yellow, hairy towards apex, internally yellow with dark red markings on side and lower lobes and at throat, hairy in upper 1/2; stamens slightly exserted. Section Aeschynanthus but atypical. Distribution: Only known from the type locality in West Sumatra.
Although not described until 1991, this most spectacular Aeschynanthus was collected in 1974 and grown at the Royal Botanic Gardens Kew, from where it was widely distributed, particularly in the USA where it is grown under the names of Sumatra Sunburst or Sarasota Sunburst.
Aeschynanthus cordifolius Hooker.
Flower. The plant
illustrated is similar to A. tricolor, and may in fact be that species despite the absence
of tricolor's yellow and black stripes. Section Aeschynanthus.
A. curtisii C.B. Clarke.
Stems pendent, glabrous; leaves glabrous, up to 7 x 3cm,narrowly to broadly elliptic, apex acute with rounded tip; inflorescence axillary or terminal, 1-2 flowered or clustered; calyx red, glossy, glabrous, up to 4cm long; corolla up to 6cm long, externally bright red and hairy, internally with yellow marks in throat; stamens hardly exserted. Section Aeschynanthus. Distribution: Brunei, Sabah, Sarawak, Kalimantan.
This alternative image shows well the markedly early maturation of the calyx which occurs in the genus and which is particularly striking in members of section Aeschynanthus. It is thought (Burtt & Woods 1975) that the calyx acts as a miniature water bath to prevent dessication of the developing flower-bud.
Aeschynanthus evrardii Pellegr.
Flowers. Seeds. Section Haplotrichium. Distribution:
Hybrid by Bill Saylor of A. micranthus x A.
Aeschynanthus guttatus P. Woods.
Vegetative stems climbing or flexuous, flowering stems usually stiffer, glabrous; leaves glabrous, grey-green, up to 8 x 3.5cm, narrowly to broadly ovate, apex acute to shortly acuminate; inflorescence axillary or terminal, single-flowered; calyx green, glabrous, up to 1cm long; corolla up to 5.7cm long, externally glabrous, yellowish green faintly lined purple, or dull orange or pinkish, internally whitish in throat and tube, lower lobes lined or speckled purplish and with 5 tufts of stout hairs near the base; stamens slightly exserted. Section Microtrichium, but atypical. Distribution: Territory of New Guinea.
Aeschynanthus hartleyi P. Woods
Section Polytrichium. Distribution: New
Aeschynanthus hildebrandii Hensl.
Yellow form, A. hildebrandii 'Topaz'. Section Haplotrichium. Distribution: Burma, Malaya
Note: The plants formerly in cultivation as A. hildebrandii have
been reassigned to the genus A. humilis.
A. longicaulis (Wallich) R. Brown. (A. marmoratus F. Moore; A. zebrinus Lemaire).
Stems spreading and arching, glabrous; leaves glabrous, up to 10 x 3cm, apex acuminate; inflorescence axillary or terminal, flowers single or paired; calyx purplish, with scattered hairs, up to 2cm long, divided almost to base; corolla up to 3.5cm long, externally green with sparse hairs, internally yellow with crimson markings extending into throat and 5 tufts of stout hairs near the base of the tube; stamens long exserted. Section Polytrichium. Distribution: Burma, Vietnam, Thailand and Peninsular Malaysia.
This species is cultivated for its beautiful leaves, dark green marbled lighter above and paler mottled purplish below, rather than for the somewhat insignificant flowers. It is one of the parents of the intersectional hybrid Black Pagoda and its influence may be seen particularly in the leaf markings of the latter.
Aeschynanthus sp. 'New Guinea'. ('Coral Flame')
Allegedly a species from New Guinea, originally
distributed as USDA Plant Introduction No. 354156. An attractive cultivar.
Aeschynanthus nummularius (Burkill and S. Moore) K. Schum (Trichosporum nummularium)
Section Microtrichium. Distribution: New
A. obconicus C.B. Clarke.
Stems spreading to pendent, sparsely hairy; leaves with scattered hairs, up to 10 x 3.8cm, broadly lanceolate to ovate-elliptic, apex acuminate; inflorescence axillary and terminal, flowers in clusters; calyx deep crimson to purple, densely hairy internally and externally, up to 1.6cm long; corolla up to 3.6cm long, externally scarlet, densely hairy, internally glabrous, cream or white in throat and tube and 3 darker lines on lower lobes; stamens hardly exserted. Section Aeschynanthus. Distribution: Peninsular Malaysia, Sumatra and Sarawak.
One of a group of species with a broadly campanulate calyx, which includes A. hians and A. tricolor.
A. pachyanthus Schlechter.
Juvenile stems climbing, hairy; flowering stems stiff, spreading, glabrous; juvenile leaves small, rounded, hairy, adult leaves glabrous, up to 10.5 x 4.5cm, elliptic, apex acuminate; inflorescence axillary or rarely terminal, single or 2-flowered; calyx green flushed black-purple or entirely black-purple, glabrous, up to 3.4cm long, tubular for about 1/2 its length then strongly asymmetrically 2-lipped, the 3 lobes forming the upper lip shorter and sometimes almost fused; corolla up to 5.4 cm long, externally glabrous and purplish, internally whitish in throat and tube and with 5 tufts of stout hairs near base of tube; stamens not exserted. Section Microtrichium. Distribution: Territory of New Guinea.
The juvenile growth of most Aeschynanthus species has smaller often rounder leaves than the adult growth, and has at least a few hairs. A. pachyanthus exhibits this very markedly; see image here. The strongly asymmetric calyx of this interesting montane species is so marked that Schlechter (1923) placed it in its own section, Anisocalyx. However unequal calyx divisions do occur elsewhere in the genus and Burtt & Woods (1975) reduced Anisocalyx to Microtrichium.
A. parviflorus (D. Don) Sprengel. (Trichosporum parviflorum D. Don; A. ramosissimus Wallich).
Stems spreading, glabrous; leaves glabrous, up to 11.5 x 2.6cm, narrowly elliptic to elliptic, apex long acuminate; inflorescences axillary or terminal, several-flowered; calyx greenish-yellow to light orange, up to 1.2cm long, glabrous, tubular in lower 1/3, lobes narrowly triangular; corolla up to 3.1cm long, externally hairy, orange shading to red apically and lobes with a crimson line, internally pale orange with a crimson mark on red-edged lobes and with a few hairs near base of tube; stamens long exserted. Section Diplotrichium. Distribution: Nepal, Bhutan, India, Burma, Thailand.
A. pulcher G. Don (Trichosporum pulchrum Blume; A. pulchra G. Don).
Stems trailing, usually glabrous; leaves glabrous, up to 6 x 2.8cm long, elliptic to ovate, apex acute; inflorescences axillary and terminal, 1--8 flowered; calyx green flushed reddish towards apex, up to 3.6cm long, glabrous or almost so; corolla up to 7.1cm long, externally deep scarlet with scattered minute hairs, internally yellow at throat and glabrous; stamens not exserted. Section Aeschynanthus. Distribution: Java.
Examples of other morphologically similar species are
A. curtisii, A. lanceolatus,
A. parvifolius and A. radicans.
Aeschynanthus radicans Jack. (Not A. radicans Wallich, which is A.griffithii R. Brown).
Stems scrambling and trailing, hairy; leaves hairy especially below, up to 4 x 2.8cm long, elliptic to ovate, apex bluntly pointed; inflorescences axillary and terminal, usually 2-flowered; calyx up to 2.1cm, green sometimes flushed reddish, hairy; corolla up to 5.5cm long, externally scarlet with white hairs, internally whitish in throat, glabrous; stamens not exserted. Distribution: Thailand, Singapore, Peninsular Malaysia, Sumatra, Java, Sarawak & Kalimantan.
Examples of other morphologically similar species are A. curtisii, A. lanceolatus, A. parvifolius and A. pulcher.
A hybrid by Poul Jensen, involving A. hildebrandii and A. speciosus.
Aeschynanthus speciosus Hooker
Flowers. Section Aeschynanthus. Distribution: Malay Peninsula, Borneo, Java.
Burtt, B.L. & Woods, P.J.B. (1975). Studies in the Gesneriaceae of the Old World XXXIX: Towards a revision of Aeschynanthus. Notes Roy. Bot. Gard. Edinb. 33: 471-489.
Schlechter, R. (1923). Gesneriaceae Papuanae. Bot. Jahrb. 58:263-283.