Plant story

Gladiolus aureus

A once wide spread species, this geophyte, endemic to the Cape Peninsula of South Africa is on the verge of extinction in the wild.

Description
Gladiolus aureus is a deciduous, winter-growing, summer-dormant cormous geophyte, 400-600 mm high. It produces three very narrow grey or greenish grey, strongly ribbed leaves that are covered with short, soft hairs. In late winter and early spring (August to September) a slender flower stem produces an unbranched spike of three to seven funnel-shaped, pale to bright golden yellow blooms. The fruit is an elliptical, dry capsule, producing numerous small, round seeds surrounded by a brown, membranous wing.

Ecology
The flowers of Gladiolus aureus are probably pollinated by honey-bees that are attracted to their bright golden yellow flowers. The flowers remain partially closed in cool, wet weather, only opening fully on warm, windless days. The ripe fruit is a dry, three-chambered capsule that splits longitudinally, allowing the light, aerodynamic seeds to be carried away by the wind.

Distribution and habitat
Gladiolus aureus is currently restricted to a single small population of 9 plants, in seasonally moist, acid sandstone fynbos, in full sun. The site is in a highly vulnerable position as it is situated in an area that falls outside the boundaries of formally protected reserves, is surrounded by dense stands of alien Acacia and Pinus trees and has been ear-marked for low cost housing by the local government.

Conservation
During 1976, 1 100 seeds collected in the wild were deposited at the Wakehurst Place Seed Bank (now the Millennium Seed Bank) in the United Kingdom, to determine whether cold storage of seed as a measure of long-term conservation was possible. This proved successful and tests carried out several years later at the seed bank showed a germination of 99% at 11º C. Gladiolus aureus has been successfully cultivated at Kirstenbosch Botanic Garden for many years and is also being grown by several specialist bulb growers in several countries. Additional seed has been harvested by the Millennium Seed Bank Project from plants at Kirstenbosch Botanic Gardens and banked in 2005. Ideally its natural habitat should be formally protected, but should this not be possible, the MSBP in South Africa have identified suitable sites in protected areas where ex situ material could be used to re-establish this species in the wild.

Gladiolus aureus was collected for the first time by Mr C.B. Fair in the southern Cape Peninsula in 1894, and was described by the Kew botanist J.G. Baker in 1896. Although known from several populations in the past, it has always been a rare species, restricted to the southern Cape Peninsula.

Story by Carly Cowell and Graham Duncan, SANBI, South Africa

Further reading

• Duncan, G.D. (1981) Gladiolus aureus Bak.-its present position. Veld & Flora 67: 17, 18.
• Duncan, G.D. (1987) Gladiolus aureus. The Flowering Plants of Africa 49: t. 1948.
• Duncan, G.D. (2002) Just holding on-spectacular geophytes in peril. Veld & Flora 88: 142-147.