AFRICAN

ORCHIDS

Habenaria Willd. Sp. Pl. 4: 44 (1805).
Synonyms:
Kryptostoma (Summerh.) Geerinck in Bull. Jard. Bot. Nat. Belgique 52: 149 (1982).
Podandria Rolfe in F.T.A. 7: 205 (1898), non Baill. (1890), nom. illegit.
Description:
Terrestrial, rarely epiphytic, herb with tuberoids or long fleshy roots.Stem unbranched.Leaves several to many, arranged along stem or clustered at the base, or with 1-2 basal leaves appressed to the ground and the cauline leaves sheath-like.Inflorescence terminal, 1 to many-flowered.Flowers usually resupinate, in African species green and/or white, rarely yellow.Sepals usually free, the dorsal sepal often forming a hood with the petals; lateral sepals spreading or reflexed.Petals entire, 2-lobed or bifid.Lip entire or 3-lobed, spurred at base; the side lobes sometimes divided; the spur long or short, slender or saccate, often inflated at apex.Column long or short; anther erect or reclinate, the loculi either adjacent or separated by a U-shaped connective; anther canals long or short, almost always adnate to side lobes of rostellum; auricles (staminodes) 2, sometimes 2-lobed; pollinaria 2, each with a sectile pollinium, long or short caudicle and a small, naked viscidium; stigmatic processes 2, long or short, usually free but sometimes joined in lower part to rostellum.
The genus Habenaria was established by Carl Ludwig von Willdenow in 1805. The name derives from the Latin habena (reins), presumably referring to the straplike petal and lip lobes, and long, slender spur, found in many species. It is one of the largest terrestrial genera, with about 600 species found in tropical, subtropical, and warm temperate areas around the world. About 200 species occur in tropical and South Africa, with the greatest number in central and southern central Africa.
Terrestrial orchids with green flowers nearly all belong to the genus Habenaria, or to its close relatives Roeperocharis and Bonatea. A few species of Habenaria have white flowers. There are also many that have green sepals while some or all of the other parts of the flower are white. All have rather narrow perianth parts, particularly the hip that is often divided into three lobes. The petals are also lobed in many of the species, with an upper lobe that adheres to the edge of the dorsal sepal and a lower lobe that hangs downwards in front of the lateral sepals or parallel with the side lobes of the lip.
The plants are also rather easily recognized, even when not in flower, by their densely leafy stems, or by two large basal leaves, fiat on the ground and sheath-covered stems. In those species with many leaves, there are often a few sheaths at the base, then a group of large leaves, and the upper part of the stem is clothed with small leaves or sheaths that gradually intergrade into the bracts.
Habitat:
Many of the grassland habitats have been so changed, either by grazing, draining or conversion to agriculture, that the places where these orchids used to grow have largely disappeared. Some of the highland and coastal habitats remain and are protected, and some rather spectacular species can be found in these areas by searching at the right time of year.
Cultivation:
Plants should be grown in a standard terrestrial mix. As with almost all terrestrial orchids, good drainage is essential. When species die back after flowering, they should be kept virtually dry during their resting period, although a light sprinkling of water can be given, perhaps once a month, to prevent shrivelling of the tubers. This is roe time to repot; old dead roots can be pulled away, but it is not necessary to repot every year, as long as roe compost is still open. When new shoots start to appear, careful watering can start, although it is best to wait until the shoots are 2.5 cm tall. Once the plant is growing strongly, water can be given more freely, although the compost should never be allowed to become soggy. In common with most terrestrial orchids, it is best to avoid getting water on the leaves. Very few of the species of Habenaria are in cultivation.
Notes:
The genus has been divided into a number of sections, depending on both vegetative and floral characters by Kraenzlin (1893), a few of which have since been accorded generic rank by some authors. A new revision, on a worldwide basis, is required to ascertain sectional limits and to update the nomenclature. But fore you can find the species you looking after have I follow the Kraenzlin (1893) below.
Habenaria section Bilabrellae
Description:
Habenaria section Ceratopetalae Kraenzl.
Description:
Most are large, often spectacular species with bilobed petals, with at least the lower lobe hornlike and sweeping upwards, and a trilobed lip. The lateral sepals are rolled lengthways when the flowers open. Stigmatic arms slender, projecting forwards, suddenly enlarged and truncate at tip. Flowers green and/or white; stem leafy.
Habenaria section Chlorinae Kraenzl.
Description:
Petals entire; lip usually trilobed but sometimes entire. Slender plants with small, green flowers and leafy stems.
Habenaria section Cultratae
Description:
Habenaria section Commelynifoliae Kraenzl.
Description:
Large plants with leafy stems; petals entire, lip either entire or trilobed
Habenaria section Diphyllae Kraenzl.
Description:
Plants with one or two basal leaves adpressed to the ground and several sheath-like leaves scattered up the flowering stem. It is a heterogeneous group comprising some species that are florally very different, and includes some of the most attractive species, several well worth cultivation. However they tend to be reluctant to flower; in the field, any colony has usually many more non-flowering than flowering plants. This is taken to extremes in some of the one-leafed species, in particular H. nyikensis, where it is possible to find literally hundreds of leaves without seeing a single flowering plant.
Habenaria section Kryptostoma Summerh.
Description:
Petals divided to about half their length, the upper lobe adnate to the dorsal sepal and the lower lobe fleshy and linear. Lip joined to column in basal part, free part trilobed. Stem leafy.
Habenaria section Macrurae Kraenzl.
Description:
Attractive plants with leafy stems and white scented flowers. Petals bilobed, lip trilobed with broad segments. Confusingly, does not include H. macrura.
Habenaria section Mirandae Summerh.
Description:
Habenaria section Multipartitae Kraenzl.
Description:
Robust plants with leafy stems; petals entire, lip trilobed, the side lobes fimbriata. These handsome plants seem to respond well to cultivation.
Habenaria section Pentaceras ((Thouars)) Schltr.
Description:
Fairly slender plants with the dorsal sepal erect, forming a hood. Petals bilobed, the lobes usually linear; lip trilobed. Stigmatic arms stout, short, lying along the lip. Flowers green or yellow-green. It is easy to recognize plants as being in this section, but many of the species are very much alike and extremely confusing.
Habenaria section Podandria ((Rolfe)) P.F. Hunt
Description:
Plants with no tuber, but fleshy roots; leaves mostly in a basal tuft.
Habenaria section Productae Summerh.
Description:
Habenaria section Pseudoperistylus P.F. Hunt
Description:
Habenaria section Replicatae Kraenzl.
Description:
Sepals all reflexed, the laterals oblique with a lateral apiculus; petals bilobed, the upper lobe erect and linear, the lower usually deflexed and hinged. Lip trilobed; spur usually with a spiral twist in the middle and an inflated apex. Flowers green or green and white with an unpleasant smell, particularly in the evening. Stigmatic arms usually slender with a truncate enlarged apex, projecting forwards.
The small flowers with hinged, motile petals and bad smell suggest pollination by flies, but presumably crepuscular flies. This is one of the largest sections, with over 20 species in Malawi, many growing in marshy areas. Three species, H. arianae, H. diselloides and H. hirsutitrunci, are anomalous in having an erect dorsal sepal, but seem to agree with the section in other ways. All of these are confined to the Nyika plateau and are not common even there.
Habenaria section Trachypetalae Summerh.
Description:
Habenaria species some not yet are in location:
Bibliography and References:
The International Plant Names Index (2010). Published on the Internet http://www.ipni.org [accessed 10/24/2010