Aristea biflora (Weim)
Common names: windowed aristea
Aristea biflora is a member of the family Iridaceae and an inhabitant the south-western Cape. It is characterized by attractive violet to purple flowers with transparent to translucent bronze windows on the lower margins.
Aristea biflora is a perennial geophyte. The flattened stem reaches a height of 200 to 300 mm and occasionally 400 mm. The flowers have spade-shaped tepals which are lilac to blue with dark green or black markings, the inner tepals with transparent to translucent bronze windows on the lower margins. Aristea biflora is characterized by its long, linear anthers; further characteristic features are the relatively few-flowered inflorescence, the green and narrowly scariously margined bracts.
Of the 33 Aristea species that occur in fynbos 18 of them are red-listed of which 10 are of conservation concern and 8 are threatened including Aristea biflora, listed as Endangered (EN).
Due to the extensive ploughing of the lowest slopes of Caledon the species has become extremely rare and according to the Red List assessment this species is experiencing an ongoing decline from alien plant infestation, incorrect burning regimes and urban expansion around the towns of Caledon and Middleton.
The railway siding where the species occurs was declared a South African Natural Heritage Site (SANHS) in 1987 to protect the largest known population of A.biflora and the only extant population of Moraea insolens, in their natural habit. The area was fenced off to curb the damage caused by trucking vehicles, and efforts were made to control the spread of alien vegetation. In April 1983 seed was collected and sent to Bolus Herbarium seed bank for conservation purposes, a precaution against loss of natural populations.
Distribution and habitat
The genus Aristea is confined to the continent of Africa and Madagascar and currently comprises about 52 species of which 33 occur in the area of Cape flora at the southern end of the continent. Aristea biflora was previously recorded from Tulbagh to Caledon, Bredasdorp and Swellendam, excluding the Cape peninsula. In recent years it has only been found in the vicinity of Caledon. It grows in gravelly-clay soils on lower mountain slopes and flats; the associated vegetation is renosterveld with elements of Fynbos and a variety of bulbs.
Derivation of name and historical aspects
The name Aristea refers to the rigid leaf tips comes from the Latin arista meaning a point.
Aristea biflora is one of 33 Aristea species that occurs in fynbos, of the 52 species mainly from southern Africa.
Little is known of its ecological requirements except that it appears to require fire to germinate, and flowers most profusely in the first year following a fire.
A.biflora closely resembles A.lugens, from which it differs in having considerably longer anthers.
In the wild, both species flower exceptionally well after summer burn; it therefore seems very likely that both species would probably respond to the smoke treatment in which ethylene (gaseous plant hormone) is released, which acts as a flower-formation stimulating hormone These two species have often been confused with each other in the herbaria.
A.biflora has no economic or cultural value except that it is a most attractive species with horticultural potential.
Growing Aristea biflora
Aristeas require full sun and good rich soil with plenty of compost or peat added and regular watering throughout the year, but especially during winter and spring. Although an established plant will not easily recover if lifted and divided, it may survive if kept moist throughout the transplanting process.
In frost-prone areas, grow in a cool greenhouse and in frost-free areas grow in a border.
The smaller species are fairly well suited to cultivation in medium-sized pots, while the larger species can be grown in the rockery, among the fynbos plants. When in growth water frequently and apply a balanced liquid fertilizer monthly, keep moist at other times. Outdoors it grows in well-drained, fertile humus-rich soil in full sun.
Propagation is by division and seed. Clumps are divided in autumn, are replanted immediately and watered thoroughly. The foliage should also be reduced by about two thirds. Sow seed in autumn for species from the winter rainfall area and in the spring for summer rainfall species. Young plants can be potted up or planted out into the garden during their second season, and flowers can be expected from the third season onwards.
Aristeas require protection when grown in very cold climates. Some of the broader-leaved members are prone to severe rust on the foliage (e.g. A.major). It needs to have a quick fire lit over it in late summer (just some leaves and small sticks will do) to stimulate it to flower. If grown in a pot it needs to be a terracotta one so it doesn't melt when the fire is lit.
- Weimark, H. 1940. Monograph of the genus Aristea, Universitatis lundensis N.F Ard 2, 36(1) 1-140.
- Du Plessis, N. & Duncan, G. 1989. Bulbous plants of Southern Africa, A guide to their cultivation and propagation. Tafelberg published Ltd.
- Manning, J. 2007. Field guide to Fynbos. Struik Publishers.
- Cape Nature, ISEP (Information System for Endangered Plants) file material. Unpublished, Jonkershoek, Stellenbosch
- Flowering plants of Southern Africa 1988-1989, 50: plate 1978
- Manning, J. 1998. Southern African Wild flowers, Jewels of the Veld
- Manning, J, Goldblatt, P, & Snijman, D. 2002. The color Encyclopedia of Cape Bulbs. Timber Press Inc.
Custodians of Rare & Endangered Wildflowers (CREW)
Plant Type: Bulb, Perennial
SA Distribution: Western Cape
Soil type: Clay
Flower colour: Black, Blue, Mauve/Lilac
Aspect: Full Sun
Gardening skill: Easy