SA Orchids: Satyrium

Satyrium is widespread in temperate and montane Africa, and two species are to be found in Asia (India, Sri Lanka, Burma). The genus comprises about 90 species, of which 37 are found in South Africa. With their small non-resupinate flowers (lip facing up) Satyrium species do not really look 'orchid-like'.

The African species of the genus grow in fynbos, grassland and miombo woodland, and can sometimes be found in extensive and dense colonies of thousands of individuals, particularly in the year after a veld fire.

Most species are pollinated by moths which are attracted by the evening-scented flowers, but pollination by carrion flies and bees also occurs in the genus. Carrion fly-pollinated Satyrium flowers emit an unpleasant carrion-like odour. Flies, apparently hoping to find a dead animal to lay their eggs in, are attracted by these flowers and pollinate them. An exciting find was the recent discovery that three South African Satyrium species are pollinated by sunbirds. Flowering of all species occurs in spring or summer.

Satyrium species have undivided globular to elongate root tubers. The erect stems are 3 to 80 cm tall and have cauline leaves (all along their stem) or basal leaves, and in the latter case mostly adpressed (pressed) to the ground. They are normally glabrous (hairless) throughout. In shape the leaves vary from ovate (round) to lanceolate (lance-shaped). Some species have sterile stems that have only foliage leaves, while their inflorescences (flowers) are borne on separate stems which lack foliage. The unbranched inflorescences are terminal and have flowers that range in colour from red, pink, white, orange, yellow and green to brown. Frequently they are speckled or dotted with darker colours.

The sepals and petals are simple organs though sometimes marginally fringed, and are basally fused to each other to a greater or lesser degree (very extensively in S. pumilum). The lip is hood-like and has a terminal tip called 'flap'. It has two spurs, one on each side of the ovary. Sometimes these spurs are reduced to shallow sacs, and very rarely they are missing altogether. The structure of the column in the centre of the flower is remarkable as it has a long stalk at the base in contrast to all other related orchids. As in many other terrestrial orchids the entire above-ground part of the plant dies at the end of the growing season and the plant becomes dormant.

A number of suspected hybrids are known in the genus Satyrium.

Cultivation

Satyrium species are not very easy to grow and are therefore seldom found in living collections. The species most commonly grown are S. carneum, S. coriifolium and S. erectum from the winter-rainfall region of South Africa.

The plants should be planted in a well drained medium in a deep pot (20 - 30 cm deep). A suitable growing medium would consist of 70 % river sand and 30 % milled pine bark or well matured compost. Decomposed pine needles are also beneficial. If the river sand is fine and compacts too much, 20 % polystyrene granules or some other inert medium should be added to improve aeration. Additionally some compost or leaf mould can be placed in the base of the pot and the rest of the medium on top. Pots can be kept under 40 % shade.

Many species grow naturally in the winter-rainfall area and these plants should be watered regularly from the time the temperatures starts dropping in autumn until mid-spring. Gradually increase the intervals between watering until in summer. From November until the end of February watering should cease, except for a very occasional damping to prevent permanent dehydration. This is a crucial dormancy period for the plants, as over-watering during this period will cause the tubers to rot. The pots should be kept cool and damp enough so as not to reach the permanent wilting point.

A handy way of keeping the medium at the available water capacity level is to grow a non- invasive, hardy herbaceous indicator plant in the same pot. The indicator plant can be weeded out when the satyrium starts to grow at the beginning of the new growth season. In the case of satyriums, a summer annual would be suitable. As soon as it appears to start wilting, drench the pot. Plunging the pots and placing a mulch of bark nuggets, wood chips, straw or pine needles on top will aid in keeping the tubers cool and prevent excessive dehydration of the medium.

Fertilisers that have been used successfully are: Nutrisol, Nitrisol, Seagro, Multifeed 10, Osmocote and Horticote.

Pests to watch for are aphids and red spider.

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