Nivenia stokoei (Guth.) N.E.Br.
Common names: Kogelberg blue stars, Stokoe's bush iris (Eng.), blousterretjie (Afr.)
The Kogelberg Biosphere is home to many wonderful indigenous plants, among them Nivenia stokoei. With its clusters of blue flowers, it is one of the most striking plants in the area, flowering in late summer at a time when little else is in flower.
Nivenia stokoei 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 80-130 mm long and 3-5 mm wide, arranged like a fan. 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 is a Rare species, known from fewer than 10 subpopulations, all within the Kogelberg Biosphere Reserve. Its population is stable and it is not threatened.
Distribution and habitat
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 (1744-1825), an avid gardener and plant collector from Scotland. 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. Stokoe (1868-1959) was a mountaineer and a collector of fynbos plants, born in Yorkshire.
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.
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, N. stokoei makes an excellent accent plant and is also suitable as a pot plant. Plant in soil with good drainage for pots, and sandy soil for outdoors 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.
- 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.
Harold Porter National Botanical Garden
Plant Type: Shrub
SA Distribution: Western Cape
Soil type: Sandy
Flowering season: Late Summer, Autumn
Flower colour: Blue
Aspect: Full Sun
Gardening skill: Challenging