The Kogelberg Biosphere is home to many wonderful indigenous plants, one of them being Nivenia stokoei. This plant with its clusters of striking blue flowers is one of the most striking plants in the area. It flowers in late summer at a time when little else is in flower.

Description
This is a low, rounded shrub, which grows to a height of between 1-1.5 m. In sheltered areas it will reach a height of 1.5 m, but in open rocky areas, plants are dwarfed. The narrow, lanceolate leaves are arranged like a fan. The leaves are 80-130 mm long and 3-5 mm wide. The inflorescence is relatively large and has about 20-40 flowers borne in terminal clusters. The flowers are usually large with a long perianth tube, 27-37 mm long. These brilliantly coloured flowers appear in middle to late summer from January to March.

Nivenia stokoei belongs to a group of plants known as woody irises. The plants are true shrubs with woody stems of a hard, brittle texture. All woody genera grow from a woody underground caudex that is resistant to fire. There are nine species within Nivenia. N. stokoei is on the Rare and Endangered list.

Distribution
It occurs at the foot of the mountains in Betty's Bay and Kleinmond. It is endemic to the Kogelberg Biosphere Reserve. It grows in open rocky sites in nutrient-poor sandstone-derived soil, which is typical for the genus.

Derivation of name and historical aspects
Nivenia is named after James Niven, an avid gardener and plant collector. The seed of N. corymbosa was collected by Niven on one of his journeys to Cape Town, and the seed was raised in the garden of his patron, George Hibbert, in Clapham, London. Plants flowered there for the first time in 1805 and were described as Witsenia corymbosa. Nivenia stokoei was only properly documented in 1924, after it was collected by T.P Stokoe, hence the species name.

Ecology
Nivenias are pollinated by flies of the family Nemestriniidae and by long-tongued bees belonging to the family Anthophorideae.

Growing Nivenia stokoei

Due to its growth form and striking blue flowers, Nivenia stokoei, makes an excellent accent plant. It is also suitable as a pot plant.

Plant in soil with good drainage for pots and sandy soil for outdoors. Plant in full sun.

It is best grown from seed. Sow seed in a seed tray, with stones at the bottom to provide good drainage. Fill tray with sandy soil and cover seeds with a thin layer of sand. Germination takes place within 5-6 weeks. This plant comes from a mediterranean-type climate, with winter rains, so be careful not to overwater in summer. If the plant is grown in a pot with sandy,well-drained soil in a sunny place, watering twice a week should be sufficient. Despite coming from nutrient poor soils, this plant will benefit from a fortnightly feed with a weak solution of seaweed-based organic fertiliser, if it growing in a sandy medium. Plants must be watered in winter if grown in a summer rainfall region. Frost tolerance is not known, but it is probably minimal.

References

• GOLDBLATT, P. & MANNING, J. 2000. Cape plants. A conspectus of the Cape Flora of South Africa. Strelitzia 9. National Botanical Institite, Cape Town and Missouri Botanical Garden.
• GOLDBLATT, P. 1993. The woody Iridaceae. Timber Press, Portland, Oregon.

Berenice Carolus
Harold Porter National Botanical Garden
March 2003