Known only from two localities, one recently discovered, this spectacularly large-flowered species is sadly frail in its magnificence, a shadow cast upon it by its Critically Endangered status. Fortunately, the recent discovery of a new locality may provide reason to believe that further suitable habitats exist for this species.
Sparaxis maculosa is a deciduous geophytic plant where the underground storage organ is a corm i.e. a vertical underground stem with papery leaves, as opposed to a bulb where the underground storage organ is a bud with thickened, fleshy scales. The corm is spherical in shape, ± 15 mm in diameter and has outer coverings of dense white fibres. Cormlets are not produced in large numbers.
Lance- to sickle-shaped leaves, 7-9, are produced, forming a fan-shaped structure. The stem is almost straight, curving above the first flower. Occasionally one or two branches form and protrude from underground. Plants usually reach a height of 100-200 mm although they may reach 300 mm on occasion.
Usually one (sometimes up to 3) flower is found per spike. They are regular in shape i.e. radially symmetrical and the six tepals are fused at the base to form an open flower with a very short, ± 7 mm long, funnel-shaped flower tube. Flowers are large, 55-60 mm diameter, and bright yellow with a dark, blackish maroon centre. The stamens and style are held in the centre of the flower, the style reaching the lower third of the anthers. The style branches are long and thin and extend between the upper third of the anthers. Seed and capsule structure is unknown. Flowering time: Flowers appear en masse in early September.
Unlike its closest ally, Sparaxis fragrans, S. maculosa is unscented. S. fragrans has an identical flower shape and similar bracts to S. maculosa but the former are more slender plants with long, narrow leaves (cf. S. maculosa which has short, lance- to sickle-shaped leaves) and pale yellow, scented flowers. S. fragrans commonly produces 1-3 flowers per spike (sometimes 5), whereas S. maculosa rarely produces more than one flower per spike and this is always larger than those of S. fragrans. One may occasionally observe a small, single or paired dark brown/black mark at the base of each tepal in S. fragrans; S. maculosa, however, displays a more obvious, heart-shaped, dark maroon mark in the lower third of each tepal.
Sparaxis maculosa is Critically Endangered, known only from two localities. in the region between Villiersdorp and Worcester. The first population was discovered in 1988 and monitored again in 2002 and 2007 by the Custodians of Rare and Endangered Wild Flowers (CREW) ; the second was only discovered as recently as September 2006 and was monitored again by CREW in 2007. Both populations are threatened by fragmentation as a result of agriculture, particularly viticulture. Alien grasses appear to be a threat at the newly discovered locality. The species has no official conservation status although both landowners are aware of its presence and have been approached by CREW. They have agreed not to disturb the natural veld where the plants are found. The Millenium Seed Bank has been informed of the species and has prioritized it as a target species for seed collection for 2008.
Distribution and habitat
The genus Sparaxis occurs only in the Cape Province and includes fifteen species. The extent of their occurrence ranges from Nieuwoudtville in the Northern Cape to Bredasdorp in the southwestern Cape. S. maculosa grows on seasonally wet clay flats in Renosterveld, a Critically Endangered vegetation type.
Derivation of name and historical aspects
Sparaxis is one of the smaller genera of the family Iridaceae. The Iris family is a large group that is well represented in southern Africa and includes well-known genera such as Moraea, Watsonia and Gladiolus.
The name Sparaxis is derived from the Greek word, sparasso, meaning one tear, pertaining to the lacerated bracts of the flower. The Latin specific epithet, maculosa, refers to the spotted markings on the tepals.
The first population of Sparaxis maculosa discovered was relatively small and it was unsure whether it represented a distinct species or whether it was a divergent population of Sparaxis fragrans. Following discovery of another population, however, it has been confirmed that the characters of the species are sufficiently distinct for it to merit taxonomic recognition.
Although not much is known about the pollination biology of this species, one could hazard a guess from the large, brightly coloured flowers and the markings at the base of the tepals (as seen in many moraeas and spiloxenes) that beetles would be attracted to it in order to carry out their foraging activities. Indeed, following personal observations where the vast majority of insects seen visiting the flowers were monkey beetles, it appears that they are the primary pollinators of these plants. These beetles are scarab beetles of the tribe Hopliini and, more specifically, form part of the furry, fast-flying group of monkey beetles of the non-embedding guild. Because they do not embed themselves in the flower for long periods of time and instead, actively move from flower to flower, they are as efficient as bees and flies as pollinators. The flower serves as a mating and feeding platform for the beetles, where the males tousle amongst the flowers for females, feed on pollen and possibly take in nectar. The markings at the centre of the flowers could play a role in attempting to increase the cross pollination of the plants by mimicking the beetles themselves. By doing so, the markings could deceive a beetle into sensing that there were already others at the flower, hereby increasing the desirability of the flower not only for feeding purposes but also by providing a potential mate.
It is also probable that bees and/or wasps pollinate the flowers, not only owing to the flower colour, but also because the anthers are held vertically away from the main body of the flower in a position in which pollen could be strategically brushed against the sides or back of visiting bees (Jonathan Colville pers. comm.).
A study conducted by Goldblatt et al. (2000) found that 90 % of insects pollinating sparaxis flowers in general were found to carry pollen of at least one other taxon of flowering plant, indicating that few of the species were specialized to attract a specific pollinator. The study conducted did not include Sparaxis maculosa, however, and therefore, further study is necessitated in order to give an accurate account of plant-pollinator relationships in S. maculosa.
Growing Sparaxis maculosa
It is hoped that seed and corms of this sparaxis may become available in due course from specialist bulb nurseries.
Sparaxis maculosa is relatively frost tolerant and may be grown ex situ outdoors if it receives sufficient moisture during the growing period; it can be grown outdoors in mild parts of the northern hemisphere. It is a winter-growing, summer-dormant species. For this reason, plant the seeds or corms in autumn between late March and early June. It is recommended for cultivation in both gardens and containers although it grows best in containers.
Place corms approximately ± 7 cm apart at a depth of about three times their height. Use a slightly acid soil mix that is light and drains easily. Improve drainage if necessary by mixing in large amounts of fine compost and medium-grain, river or industrial sand. One successful grower used broken peach pips (without the kernel) to improve texture. Choose a site with a slight slope to enhance drainage; a rockery is ideal. They prefer a position in full sun to flower well but can cope well in semi-shade as long as they receive at least a few hours of direct sunlight a day.
Water well after planting, then cease watering until the leaf shoot appears. After the shoot has emerged, add some bonemeal and a small amount of potassium sulphate. Avoid inorganic fertilizers. Water well once a fortnight during winter and spring in order to keep the soil permanently moist.
After the flowering season, when the leaves die back, stop all watering. Preferably remove corms from the ground every second year during the dormant period. If they are left in the ground, ensure that they are kept dry and protected against overheating. If your garden is wet in summer, remove the corms and store them until autumn. If the soil has good drainage and the corms are left in the ground, feed them with a few dressings of bulb food in order to encourage flowering the following year.
Pot corms in a medium consisting of two parts coarse river sand, one part loam and one part fine compost. Rather choose a loose, coarser mix than heavy, compacting soil. Make sure the drainage holes in the base of the container are large and place some bark or stones in the base of the container, then fill with the mix. If the soil has not been sterilized, pour boiling water into the pots to kill off most of the weed seeds. Plant corms at a depth of about 3 cm. Be sure to place the pots in an area where they will not overheat in summer and place them under cover in areas of heavy winter rainfall to prevent the corms from rotting. To prevent overheating, shade the base of the pot with stones or other potplants. Do not water in the dormant period and store containers in a cool dry area until March the following year.
It grows easily and rapidly from seed and can live for ± 10 years. It has been known to flower after one year of planting out (although they usually flower in the second spring). Sow seeds in a seed tray in autumn, preferably in a sterilized medium of equal parts river or industrial sand and fine compost or loam. Cover with a layer of sand so that the seeds are at least 10 cm deep. Keep the seedlings in the seed tray for at least one full season (preferably two) before planting out into pots or the garden. Keep the seed tray out of the rain for the first season, in a bright, airy place.
Sparaxis maculosa may produce cormlets. Remove them from the corm in the dormant period and store them until planting out in autumn, as for corms.
Pests, disease and other ailments
Pests do not pose a major problem to the species, although slugs and snails may cause extensive damage to the foliage. Sprinkle salt on the slug or snail, or place tobacco dust around the base of the plant. Mealy bugs and aphids may attack them, as may be the case for any geophytic plant.
Other pests that have posed a problem in Kirstenbosch Gardens are moles and porcupines, resulting in the species being kept potted in the collections nursery most of the time and displayed in the conservatory.
Water in the mornings rather than late in the day, to help prevent disease.
Best use in a garden
Although planting out in the garden is not highly recommended, if you choose to do so, plant them close together in groups of 25 to 50 to maximize the effect of the display. They should flower readily for about five years, although it may be difficult to keep them going thereafter. Interplant with low-growing spring annuals such as Heliophila coronopifolia, Felicia elongata, Dimorphotheca pluvialis or intersperse amongst groundcovers such as Asystasia gangetica or Sutera cordata.
References and further reading
- Barnhoorn, F. 1995. Growing bulbs in southern Africa. Southern Book Publishers, Cape Town.
- Brown, N. & Duncan, G. 2006. Grow fynbos plants. Kirstenbosch Gardening Series. South African National Biodiversity Institute, Cape Town.
- Du Plessis, N. & Duncan, G. 1989. Bulbous plants of southern Africa. Tafelberg, Cape Town.
- Germishuizen, G. & Meyer, N.L. (eds). 2003. Plants of southern Africa : an annotated checklist. Strelitzia 14. National Botanical Institute, Pretoria.
- Goldblatt, P. 1969. The genus Sparaxis. Journal of South African Botany 35: 219-252.
- Goldblatt, P. 1992. Phylogenetic analysis of the South African genus Sparaxis (including Synnotia ), (Iridaceae-Ixioideae), with two new species and a review of the genus. Annals of the Missouri Botanical Garden 79: 143-159.
- Goldblatt, P. 1999. Sparaxis. Flora of southern Africa vol. 7, part 2, fasc. 1: 151-169. National Botanical Institute, Pretoria.
- Goldblatt, P. & Manning, J. 2000. Cape plants. A conspectus of the Cape flora of South Africa. Strelitzia 9. National Botanical Institute, Cape Town.
- Goldblatt, P. et al. 2000. Adaptive radiation of pollination mechanisms in Sparaxis (Iridaceae: Ixioideae). Adansonia, ser. 3, 22: 57-70.
- Kesting, D. 2001. Botanical names: what they mean. Flora Documentation Programme, Muizenberg.
- Leistner, O.A. (ed.). 2000. Seeds plants of southern Africa : families and genera. Strelitzia 10. National Botanical Institute, Pretoria.
- Manning, J.C., Goldblatt, P. & Snijman, D. 2002. The color encyclopedia of Cape bulbs. Timber Press, Portland & Cambridge.
- Powrie, F. 1998. Grow South African plants. National Botanical Institute, Cape Town.
- Smith, C.A. 1966. Common names of South African plants. Memoirs of the Botanical Survey of South Africa No. 35.
Caitlin von Witt
Custodians of Rare and Endangered Wildflowers