Spiloxene

Salisb.

Family : Hypoxidaceae
Common names: golden star (Eng.); sterretjie (Afr.)

Spiloxene capensis:Photo:Colin Paterson- Jones
© Colin Paterson-Jones

At the height of the Cape's spring season, species of the genus Spiloxene offer flower seekers fine displays of brilliant, floral stars.

Description
The name Spiloxene is derived from the Greek spilos, a spot, and xenos, a host or a stranger, which emphasizes the dark spots commonly found in the centre of the flowers of the widespread and well-known S. capensis.

Spiloxene is a relatively uniform group of small, deciduous plants which seldom reach a height of 500 mm. The rootstock is a corm which is replaced annually after each growing season. Most often the desiccated corms of the previous seasons persist for a year or more in a vertical series. Exceptions are S. alba and S. aquatica where the corms are arranged almost horizontally.

The various corm coverings are sufficiently diagnostic to allow Spiloxene species to be placed in fairly easily recognizable groups. Species with thin-textured and finely-veined leaves usually have thin, membranous corm coverings, but if the leaves are firm and coarsely veined then the corm tunics are fibrous. When the fibres are branched they form a fine, closely woven net over the corm, but when they are hard and straight, they resemble the teeth of a comb.

All Spiloxene species have contractile roots at some stage of their development. These regulate the depth of the corm in the ground and help to optimise the plant's growth. Remarkably, the roots of S. ovata and S. gracilipes twist around the corm and persist from one year to the next as a dense covering of hard, coiled roots. This nongeotropic growth pattern has seldom been reported in other geophytic plants and appears to be unique within Spiloxene.

Commencing in late autumn, the foliage grows into a basal tuft of more or less three-ranked leaves. These vary from narrowly lance-shaped to cylindrical or linear. Spiloxene aquatica, which inhabits seasonal pools, is exceptional in having somewhat hollow leaves, largely filled with air spaces. Unlike their well known relatives, Hypoxis and Rhodohypoxis, plants of Spiloxene are entirely smooth, except for a few species that have inconspicuous, shortly branched hairs on the leaf margins.

Each inflorescence consists of a slender, leafless scape which terminates in a few, often inconspicuous bracts and one or two (rarely up to seven) flowers with long, slender pedicels. As is typical in the family Hypoxidaceae, the flowers have six tepals, six stamens, a three-chambered, inferior ovary, and a three-branched style. Flowers are uniformly star-shaped and mostly golden or pale yellow in colour, but in a few species they are white and rarely pink. Distinct red and green stripes often line the backs of the outer tepals in species such as S. capensis and S. canaliculata, however, most often the backs of the outer tepals are plain reddish pink or green. The largest and most striking flowers are those of S. capensis and S. canaliculata which also have dark spots or 'eyes' at the base of the tepals. In S. capensis the spots are generally blackish and occasionally iridescent blue-green, whereas those in S. canaliculata are deep, matt purple.

Spiloxene species are predominantly spring flowering and since they produce a succession of inflorescences each season they continue to flower for a month or more. Generally they are sun-loving, so the flowers remain closed if conditions are cold or wet, often for several days at a time, until the weather improves. Even on warm days the flowers open for only a few hours, usually between 11am and 4 pm.

The seeds are produced in capsules that open when the spent floral parts drop off. When shaken, the capsules drop their seeds directly on the ground from where they may be washed away to other sites. The seeds are unusually tiny (0.4-1.0 mm long) and have a distinctively sculptured, dark brown, brittle coat.

Conservation Status
The most recent Red Data assessment recognised five vulnerable or endangered species of Spiloxene. These are confined to the lowlands of the southwestern Cape where the major threat is habitat loss through the ploughing of arable land and the persistent spread of housing estates.

Distribution
Spiloxene has about 25 species, several of which are yet to be formally described. As presently understood, the genus is confined to areas of southern Africa experiencing rainfall in winter or throughout the year. Eighteen species are found in Western Cape, eight species are known from Northern Cape and three species come from Eastern Cape. They range from the coastal forelands to high altitudes on the Cape Fold Mountains and the inland escarpment. Habitats are mostly seasonally damp sites such as seasonal pools, seepage areas, stream banks, and wet rock ledges. The recently described S. pusilla, with its delicate, pale green leaves and minute flowers, shelters in deep recesses below overhanging rocks.

Ecology
Like all Hypoxidaceae the flowers of Spiloxene have no nectaries; therefore the only reward to visitors is pollen. Nevertheless, the open, star-shaped flowers have prominently exposed anthers which are well suited to attract pollen-collecting insects that lack specialized foraging behaviour. The main pollinators are thought to be bees. Spiloxene capensis and S. canaliculata, however, belong to a species-rich guild of Cape plants that have flowers with dark, central markings which hopliine (Scarabaeidae) beetles use as visual cues to locate pollen and as suitable sites for mating. Because of the importance of pollen as an attractant, it is quite possible that the closing of Spiloxene flowers under unfavourable conditions minimizes the loss of pollen which, unlike nectar, is not a resource that can be renewed.

Economic and cultural value
In contrast to the medicinal and horticultural importance of Hypoxis and Rhodohypoxis, the genus Spiloxene has not gained any commercial value.

Species

The following species reflect some of the diversity within Spiloxene in terms of plant size, flower colour, and habitat:

S. aquatica.Photo Colin Paterson-Jones

S. aquatica (L.f.) Fourc.: plants 155-400 mm tall; corm smooth or rarely fibrous above. Leaves 2-5, erect, hollow, exceeding the inflorescence, linear, and ± 3 mm wide. Flowers 2-7 per scape; tepals 5-17(-35) mm long, white with green backs, often scented; bracts 2 or more, green, clasping the pedicels towards the base. Flowering June to October. In seasonal pools and streams from Namaqualand to Cape Peninsula and Swellendam.
S.canaliculata. Photo C. Paterson-Jones
S. canaliculata Garside: plants 100-350 mm tall; corm with a cap of short, hard bristles. Leaves 2-5, recurved, 2-4 mm wide, U-shaped in cross-section, margin bearing minute teeth when young. Flower 1 per scape; tepals 25-45 mm long, orange to yellow with a dark purple, non-iridescent centre, backs with reddish stripes; bract 1, long, green, tightly sheathing the pedicel. Seeds J-shaped. Flowering July to October. Localized on seasonally wet, clay flats near Darling.
S. capensis . Photo. C Paterson-Jones

S. capensis (L.) Garside: plants 100-350 mm tall; corm with a cap of short, fine bristles. Leaves 2-8, recurved, 3-15 mm wide, V-shaped in cross-section, distinctly keeled, margin often thickened, usually bearing minute recurved teeth. Flower 1 per scape; tepals 15-35 mm long, white, cream, yellow to orange, rarely pink, unspotted or with an iridescent or non-iridescent dark centre, backs greenish, usually lined with red; bract 1, long, green, tightly sheathing the pedicel. Flowering July to October. On seasonally wet flats from Clanwilliam to Cape Peninsula, Oudtshoorn, and western Karoo.

S. minuta. Photo C Paterson-Jones
S. minuta (L.) Fourc.: dwarf plants 10-70 mm tall; corms woody with a broad, flat base. Leaves usually 3, recurved, 1-2 mm wide, firm and channelled. Flowers 2 per scape; tepals 4-6 mm long, white with green backs, scented; bracts 2, narrowly lance-shaped, clasping the pedicels at the base, pale green. Flowering April to June. In patches on damp, clay flats from Clanwilliam to Cape Peninsula and Gordon's Bay.

S.monophylla.Photo Colin Paterson Jones

 

S. monophylla (Schltr.) Garside: small plants 20-100 mm tall; corm covered with fine, branched fibres. Leaf 1(-2), spreading, 1.5-2.0 mm wide, firm, shallowly channelled. Flower 1, on a subterranean scape; tepals 10-35 mm long, yellow with pale green backs, much longer than the stamens and style; bract 1, lance-shaped, green to whitish, clasping the pedicel towards base. Flowering December to March, especially after fire. On sandstone slopes from Kogelberg to Elim.

In the Garden
In general, Spiloxene species make poor garden subjects as they have individual watering requirements. The plants need to be kept dry in summer and they like to be inundated during winter. Nevertheless, the peacock-coloured flower forms of S. capensis are a deserving choice for the specialist bulb grower with an interest in pot plants.

References and further reading

  • Leistner, O.A. (ed.). 2000. Seed plants of southern Africa : families and genera. Strelitzia 10. National Botanical Institute, Pretoria.
  • Manning, J., Goldblatt, P. & Snijman, D. 2002. The color encyclopedia of Cape bulbs. Timber Press, Oregon and Cambridge.
  • Nel, G. 1914. Die afrikanischen Arten der Amaryllidaceae-Hypoxideae. Botanische Jahrbücher 51: 287-340.
  • Smith, C.A. 1966. Common names of South African plants. Memoirs of the Botanical Survey of South Africa No. 35.
  • Thompson, M.F. 1969. Spiloxene capensis and S. canaliculata. The Flowering Plants of Africa 39: 1557A & B.

 

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Author
Dee Snijman
Compton Herbarium, Kirstenbosch

Images
Colin Paterson-Jones
Fernwood, Cape Town

September 2007

 

 

 

 

 

 

 


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