Geissorhiza eurystigma is one of the few species in its genus with such large and colourful flowers. The combination of purple and red is indeed a beautiful sight, especially in areas where they grow in mats around your feet.
Geisshorhiza eurystigma is a very attractive geophyte with deep purple flowers with a red centre. The red is sometimes also outlined with light purple, which becomes darker towards the tepal tips. The anthers are distinctively broad and very furry. The plant reaches a height of 80-150 mm (sometimes 200 mm). The corm is round (globose) and more or less symmetric. Each plant has 3 leaves and each leaf is conspicuously ribbed. The bracts are green and become dry and membranous from the apex. They often becomes reddish on the upper margin.
Geissorhiza eurystigma is classified as EN (Endangered) in the South African Red List. The species is threatened by wheat farming, trampling by cattle and sheep, severe invasion by alien grasses and eutrophication. Over 80% of this species' habitat has been lost to crop cultivation leaving only five known localities for this species, but these too are in decline.
Distribution and habitat
Geissorhiza eurystigma is endemic to the Cape Floral Region (CFR) of South Africa occurring on the Western Cape coastal belt, centred around Darling and Mamre, and the range extends southeast towards Kalbaskraal. In natural conditions this species occurs in granitic soils in the renosterveld vegetation type.
Derivation of name and historical aspects
The genus name Geissorhiza is derived from the Latin words geisson, meaning ‘tile' and rhiza, meaning ‘root'. Much like the tiles on a roof there is regular overlapping of the corm tunics. The specific name eurystigma refers to the broad feathery nature of the stigma. This genus consists of about 100 species which are very florally diverse, with adaptation to various habitats and pollination syndromes.
Geissorhiza eurystigma was first described by Daniel de la Roche (1766), who named it Ixia secunda. This species was misidentified and later in 1800s, renamed G. eurystigma . Geissorhiza eurystigma was often confused with G. radians because of its similar flower form and colour, but in 1931 Louisa Bolus described it as G. eurystigma, referring to its unusual and conspicuous style branches.
This species is not self-compatible and needs to be cross-pollinated to set viable seeds. A pollinator-rich garden is therefore needed to ensure seed set. Due to the dark centre of the species it is mostly like be pollinated by monkey beetles from the Scarabaeidae: Hopliini.
Uses and cultural aspects
Although a relatively large genus, they are of little horticultural value except to specialist collectors, because of the small inconspicuous nature of the flowers of most species. Geissorhiza eurystigma is one of the species with large flowers and has quite brilliant colouration that would be an asset to any garden.
Growing Geissorhiza eurystigma
Geissorhiza is best planted in dense stands on raised beds or in 20–25 cm containers. The plants require constant moisture throughout the growing period and excessive desiccation will result in rapid flower bud abortion, yellowing of leaves and premature dormancy. However, during natural dormancy, corms must be kept completely dry. Plants need full morning sun or bright light for as much of the day as possible. Flowers only open fully on hot, still days.
Sow seeds in autumn and remove cormlets developing around the mother corm in late summer. Seedlings flower in the second season after planting, but in ideal conditions, may flower within 8 months.
Pests and pathogens
Flowers are sometimes attacked by aphids and the plants can contract viral diseases. Mealy bug may infest the corms, and corms are also a delicious treat for porcupines and molerats.
References and further reading
- The free dictionary: http://www.thefreedictionary.com/eury- (10/10/2020)
- Duncan, G. 2000. Grow bulbs: a guide to the cultivation and propagation of the bulbs of South Africa and neighbouring countries. South African National Biodiversity Institute, Cape Town.
- Goldblatt, P. 1985. Systematics of the southern African genus Geissorhiza (Iridaceae-Ixioideae). Annals of the Missouri Botanical Garden 72: 277 – 447.
- Manning, J., Goldblatt, P. & Snijman, D. 2002. The color encyclopedia of Cape bulbs. Timber Press, Cambridge.
Brittany Arendse & Anri Marais