Satyrium princeps

Bolus

Family : Orchidaceae (orchid family)
Common name : ‘Rooi-trewwa' (Afr.)

Part of flower stalk

Satyrium princeps is a handsome but threatened terrestrial orchid from coastal sands in the southern part of the Western and Eastern Cape. Its long-lasting carmine-red flowers appear in spring and early summer and are pollinated by sunbirds.

Description
The rootstock of this deciduous, winter-growing geophyte is a root-stem tuberoid, a storage organ which consists of both root and stem tissue. The plant reaches up to 86 cm high in flower and has two broadly oval leaves which are prostrate and fleshy. The upper leaf surface has a thick, transparent, water-storing epidermis.

Leaves

The sturdy brownish maroon flower stem has 7–9 prominent dry, membranous sheaths, and the dense, erect spike consists of deep carmine-red, unscented or sometimes faintly sweet-scented flowers. Flowering takes place from September to November, with a peak in October.

At the beginning of the growing season in late autumn, a new shoot develops from the apex of the tuberoid, which forms the regenerative bud. As the shoot develops, adventitious roots grow from the base of the stem where it is attached to the tuberoid, and at the same time, a replacement tuberoid also develops there, resulting in the plant having two tuberoids during its active growth phase: the old one that formed during the previous winter season, which gradually withers, and the new one that develops during the current winter season and sprouts anew the following autumn.

Flower stalk

Satyrium flowers are non-resupinate, meaning that the hood-like labellum (lip) is the uppermost floral segment, while the sepals and petals face downwards. S. princeps is most closely allied to the pink- or rarely white-flowered S. membranaceum which flowers simultaneously but differs in its more slender habit, shorter spikes and narrower lateral sepals. Its distribution overlaps with S. princeps in the southern Eastern Cape but it has a wider distribution in the northern Eastern Cape, extending to Lesotho. S. membranaceum is night-scented and pollinated by hovering hawkmoths.

Conservation status
Satyrium princeps is a protected species. It is also a threatened species as m uch of its former habitat has been lost to coastal housing development, agricultural expansion and infestation by alien plants, especially Australian acacias. Its current conservation status is categorized as Vulnerable.

Distribution and habitat
Satyrium princeps is only known from a few sites in the region extending from Wilderness in the southern Cape to Port Alfred in the Eastern Cape. It occurs in full sun on fixed littoral dunes in small to large colonies and is locally plentiful in deep sand among low scrub or grasses, from sea level to 150 m. It occurs in Southern Cape Dune Fynbos, Algoa Dune Strandveld and Albany Dune Strandveld vegetation types.

Derivation of name and historical aspects

The generic name Satyrium is probably derived from the satyr, a half-man, half-goat with two budding horns in Greek and Roman mythology, and alludes to the two-spurred lip of the flowers which occurs in most satyrium species. The goat-like smell of the flowers of certain species is an alternative theory.

The Swedish taxonomist Olof Peter Swartz first described the genus Satyrium in 1800. S. princeps was described in 1888 by the English orchidologist Harry Bolus, [Bolus was a businessman who spent most of his life in S.A. and studied orchids as a hobby] in volume 18 of the third series of Hooker's Icones Plantarum, accompanied by an illustration by the British botanical artist Matilda Smith. The Latin specific epithet princeps refers to the ‘princely' or ‘most distinguished' appearance of the inflorescence.

Satyrium has about 90 species, distributed mainly in temperate, tropical and montane Africa. Thirty-eight species occur in southern Africa and the genus is centred in the winter-rainfall zone, in the south-western and southern parts of the Western Cape.

Ecology
Satyrium princeps is adapted to a winter growth cycle of rapid vegetative growth during the cool, moist winter months, flowering in late spring and early summer as temperatures rise, and displaying desiccation of the above-ground parts and complete dormancy during the hot summer.

The flowers are pollinated by Southern Double-collared Sunbirds ( Nectarinia chalybea ) and Black Sunbirds ( Nectarinia amethystina ). These mainly nectar-feeding birds cling to the sturdy flower stems and insert the tips of their beaks into the upper part of the labellum (lip) spur, then suck up the rest of the nectar by extending the tongue to the base of the spur. During this process, large pollinia (a coherent mass of pollen grains) become attached to the beak of the bird and are deposited onto the stigma of flowers visited subsequently.

Once ripe, the cell walls of the cylindrical seed capsules split open and the minute seeds are dispersed by the shaking action of wind.

Uses and cultural aspects
Satyrium princeps is used to a very limited extent as a container subject in ornamental horticulture by specialist bulb growers. It has no traditional, economic or medicinal uses. The most important South African Satyrium species in cultivation are probably S. carneum, S. erectum and S. odorum.

Growing in a pot at Kirstenbosch

Growing Satyrium princeps

Several winter-growing satyriums including S. princeps are outstanding subjects for display in containers and they are generally of much easier culture than the summer-growing species. The latter, especially those of marsh and wetland habitats, are probably greatly dependent on association with mycorrhizal fungi and soil specificity, and are usually short-lived in cultivation. S. princeps performs very well in the bulb nursery at Kirstenbosch in deep, 20–25 cm diam. plastic pots. With careful attention to growing medium, watering procedure and maintenance of a summer dormant period, this species is generally long-lived, sometimes lasting up to 20 years.

It needs full sun or bright light to flower well, and a stake is best inserted at planting time (so as not to damage the delicate tuberoid during the growth phase) to prevent stems from falling over in strong wind. Plant the tuberoids with their tops 10–20 mm below the soil surface, in a very sandy, acid growing medium such as six parts of washed silica sand and one part of finely milled, composted bark, with a 20–30 mm layer of well-rotted compost placed at the base of the container over the drainage chips. Exercise care when handling the tuberoids as they are easily bruised, and should not be stored in open air as they rapidly desiccate and perish. Should it become necessary to transplant actively growing specimens, take great care, as the tuberoids easily become detached from the base of the stem.

Watering procedure is of critical importance. Start with an initial drench in late autumn, then wait until the new shoots appear, followed by a drench about once every 10 days, allowing the medium to dry out somewhat before the next drench is applied. The plants respond well to liquid fertilizer applications with high potassium but low nitrogen content. Since the plants flower in late spring and early summer, it is necessary to continue watering for as long as possible in order to maintain pleasing green leaves while the plants are in flower, failing which, the leaves may turn yellow. After flowering or as soon as the leaves start to desiccate, cease all watering and maintain a completely dry summer rest period.

Adult tuberoids usually form a single replacement tuberoid but sometimes two or three are produced and these can be separated and replanted immediately into dry soil in late summer, before active growth begins. Unfortunately the seeds of S. princeps cannot be stored for long periods because they contain very small food reserves, and can only be raised when sown in sterile laboratory conditions in special growth media.

The tuberoids are subject to fungal rot if not grown in well drained soil and kept dry in summer.

References and further reading

  • Botes, C. 2007. Christo Botes on satyriums. Newsletter of the Algoa Branch of the Botanical Society of South Africa 4: 2–3.
  • Crous, H.T. & Duncan, G.D. 2006. Grow disas. Kirstenbosch Gardening Series . South African National Biodiversity Institute, Cape Town.
  • Duncan, G.D. 2011. Satyrium princeps . Curtis's Botanical Magazine 28,3: 160–-168.
  • Du Plessis, N.M. & Duncan, G.D. 1989. Satyrium . Bulbous plants of southern Africa. Tafelberg, Cape Town.
  • Hall, A.V. 1982. A revision of the Southern African species of Satyrium .Contributions from the Bolus Herbarium 10: 1–142.
  • Hall, A.V. 1999. Satyrium . In: H.P. Linder & H. Kurzweil, Orchids of Southern Africa. A.A. Balkema, Rotterdam.
  • Johnson, S.D. 1996. Bird pollination in South African species of Satyrium (Orchidaceae). Plant Systematics and Evolution 203: 91–98.
  • Mucina, L. & Rutherford, M.C. 2006. The vegetation of South Africa, Lesotho and [run on]Swaziland . Strelitzia 19 . South African National Biodiversity Institute, Pretoria.
  • Skead, C.J. 1967. The sunbirds of southern Africa . A.A. Balkema, Cape Town.
  • Von Staden, L., Liltved, W.R., Oliver, E.G.H. & Oliver, T.A. 2011. Satyrium princeps Bolus. National Assessment: Red List of South African Plants version 2012.1.

 

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Kirstenbosch National Botanical Garden

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