This well known indigenous large wild iris is commonly grown in gardens and used in large landscapes throughout the country. It is a perennial, evergreen plant which grows up to 1.5m in large clumps. It grows naturally along the eastern coastal areas of the southern Cape, Eastern Cape and southern Kwazulu-Natal where it may be found in full sun or partial shade at forest margins, or in the shelter of taller shrubs on exposed slopes facing the sea.

The name Dietes means "having two relatives" and refers to the relationship between this genus and Moraea and Iris. Grandiflora means "large flower".

Dietes grandiflora plants grow from underground rhizomes. The long, rigid, sword-shaped leaves are held in a fan shape. The leaves are dark green and may reach up to 1m long and 15-20mm wide.

The attractive flowers are large (about 100mm across) and are white with yellow nectar guides and outer tepals and violet central segments. The flowers are held on erect, slender stems which are about 1m in length.

The flowers are borne in mass at certain periods - often after rain in summer. The individual flowers do not last more than a couple of days (so are of no use in a vase) however, the plant bears so many flowers during the peak period that the plant looks most striking. The flowers attract lots of bees and other pollinators.

This plant is occasionally called the "Fairy Iris" because the fragile white petals not only look like fairy wings, but also have a tendency to disappear mysteriously overnight!

The large wild iris fruit is a large capsule up to 45mm which is held erect and splits open to release shiny, dark brown seeds.

Growing Dietes grandiflora

This is a popular, easy-to-grow garden plant which will grow under most conditions. The plants are both frost and drought hardy and will grow in either sun or shade. However, for best results and most flowers, plant Dietes grandiflora in full sun or light shade in well composted, well drained soil and water well in summer.

It has become a popular landscaping plant due to its reliability and hardiness and is often found in parking areas at shopping centres, schools etc. It can be effectively used in mass plantings, but is also effective in mixed plantings or used as an accent plant alongside a pond or some steps.

The large wild iris is easy to propagate from seed sown in spring or by dividing large clumps which spread by means of rhizomes. They multiply rapidly and are soon ready to be split again.

There are six species of Dietes - five of which occur in South Africa - and one on an island in the Tasman Sea (between New Zealand and Australia). Dietes were once called Moraea (a closely related group), but were separated because Dietes have a rhizome, whereas Moraea have a true corm.

References

• Batten, A. 1986. Flowers of Southern Africa. Frandsen Publishers : Sandton
• Eliovson, S. 1984. 7th ed. Wild Flowers of Southern Africa.
• Joffe, P. 2001. Creative Gardening with Indigenous Plants - A South African Guide. Briza Publications : Pretoria
• Pienaar, K. 1985. Grow South African Plants Struik Publishers : Cape Town
• Pooley, E. 1998. A Field Guide to the Wild Flowers of KwaZulu-Natal and the Eastern Region. Natal Flora Publications Trust : Durban
• Van der Spuy, U. 1971. Wild Flowers of South Africa for the Garden. Hugh Keartland Publishers : Johannesburg
• Walker, J. 1996. Wild Flowers of KwaZulu Natal. W.R.Walker Family Trust : Durban

SHARON TURNER
Witwatersrand National Botanical Garden
December 2001