TALK GIVEN at the MELVILLE KOPPIES AGM
ALLAN ABEL - 19TH AUGUST 2006.
What is an Orchid?
Orchids are evolutionary very advanced plants belonging to the order Orchidaceae, which is one of the largest orders of flowering plants. There are approximately 25 000 described species and many more awaiting either scientific description or discovery. They can be found in almost every ecological habitat, with the exception of areas of permanent ice or extreme desert, and they do not grow underwater. They are found on all the continents except for Antarctica, but are particularly numerous in northern South American and south-east Asia.
The plants and blooms come in a bewildering variety of shapes, sizes and colours. Orchid plants vary from miniatures species which can fit in a sewing thimble (Notlyia mirabilis) to those weighing a tonne or more (Grammatophyllum speciosum).The flowers also exhibit tremendous variation in size with those of Angraecum pusillum(a Southern African species) only 5mm in diameter, whilst Phragmipedium caudatum has pendant petals that can reach a length of 700mm.
Orchids can be either epiphytic (growing on trees), lithophytic (growing on rocks), terrestrial (growing on the ground) or, rarely, saphrophytic (growing in a symbiotic relationship with a fungus in the soil). It must be emphasised that epiphytic orchids are not parasites. They have evolved to take advantage of the favourable growing conditions that are available in the forest canopy than is available on the dark forest floors.
How to recognise an orchid flower?
For the layman, there are several characteristics of an orchid flower which are helpful in identifying the flower as belonging to an orchid species.
- The flower comprises 2 whorls of 3 parts each – 3 outer sepals and 3 inner petals. The one petal is usually very different in shape, colour and marking from the other petals, and is know as the labellum or lip. The function of the lip is to attract and direct pollinators to the pollinia.
- When the flowers are flattened, they can be divided into mirror halves only vertically and not horizontally.
- The most distinctive characteristic are the sexual parts of an orchid flower. The separate pistils and stamens have combined into a single structure known as the gynostemium or column. The pollinia (pollen masses) are usually located near the tip of the column under an anther cap. The stigmatic surface can be located anywhere on the column, but often just below the anther cap. The pollen is united into masses called pollinia, usually in two or four pairs. The pollinia are not powdery but range from jelly-like to hard masses.
Orchids of Southern Africa
There are currently 466 orchid species in 52 genera to be found in the area south of the Cunene and Limpopo rivers. Of these, 302 (65%) are endemic, which means they are found here and nowhere else in the world. Eight species have only been recorded only once and five species have become extinct (3 Disa and 2 Holothrix species).
Gauteng has only 52 recorded species belonging to 12 genera. The largest genera are Eulophia (15 species) and Habenaria (14 species), and the vast majority are terrestrial species.
The following species are found in the Melville Koppies Nature Reserve.
Bonatea porrecta
Size:up to 65cm.
Leaves:withered and dry at flowering.
Flowering season:June – August.
Distribution:from Eastern Cape to Limpopo, Botswana and Mozambique.
Habitat:
Bonatea speciosa var. antennifera
Size:up to 100cm
Leaves:leaves fully developed at flowering.
Flowering season:March - April
Distribution:Northern South Africa, Botswana, ZimbabweMozambique
Habitat:Grasslands, often under trees and shrubs
Eulophia clavicornis
var clavicornis(pale lavender lip)
var inequalis (yellow lip)
Size:up to 30cms
Leaves:just beginning to shoot at flowering
Flowering season:August – December
Distribution:eastern South Africa from Port Elizabeth to Kruger.
Habitat:grassland often in rocky and well-drained areas.
Eulophia ovalis ssp. bainsii
Size:up to 65cm.
Leaves:leaves 50%-100% developed at flowering.
Flowering season:December – January.
Distribution:Widespread from eastern Free State to tropical East Africa.
Habitat:grassland or stony thornveld, in dry to seasonally marshy areas.
Eulophia welwitschii
Size:up to 90cm
Leaves:leaves partially or fully developed at flowering.
Flowering season:November – January.
Distribution:northern-eastern South Africa and widespread in tropical Africa.
Habitat:grassland in dry to seasonally marshy areas.
Habenaria barbertonii
Size:up to 40cm
Leaves:about 10, regularly arranged (cauline) on the stem and fully developed at flowering.
Flowering season:February – March.
Distribution:Gauteng and Mpumalanga.
Habitat: rocky hillsides from 1000 - 1500 meters in altitude.
Habenaria filicornis (syn chlorolitica)
Size:up to 60cm
Leaves:few, regularly arranged (cauline) on the stem and fully developed at flowering.
Flowering season:February – March.
Distribution:northern South Africa, Botswana and tropical Africa.
Habitat:seasonally damp or marshy grasslands.
Habenaria dreggeana
Size:up to 40cm
Leaves:two basal leaves, pressed against the ground.
Flowering season:January – April.
Distribution:eastern South Africa, Zimbabwe, Angola, ZaireUganda.
Habitat:grassy slopes from 300m to 2000m in altitude.
Habenaria epipactidea
Size:up to 60cm
Leaves:stem is densely leafy.
Flowering season:January - March
Distribution:eastern South Africa, Zimbabwe, Angola and East Africa.
Habitat:
Holothrix randii
Size:up to 40cm
Leaves:two basal, dormant at flowering
Flowering season:September - December
Distribution:northern South Africa, Zimbabwe, Tanzania
Habitatgrassy slopes and rocky ledges
NB:On the Endangered Species list!