Barleria rigida Nees (Synonym Barleria rigida Nees var. ilicina (E.Mey.ex T.Anderson) Oberm.)
Common names: scorpion thistle (Eng.); skerpioendissel (Afr.)
A prickly barleria from the Kalahari, ideal for sunny rockeries and waterwise gardens, it is frost hardy and drought tolerant.
A much-branched shrublet, up to 400 mm high. The stems arising from a woody rootstock. Younger stems are covered with hairs, whereas the older stems become glabrous. The leaves are ovate or elliptic-ovate, blueish green and the leaf margins are thickened and wavy with spines and sometimes white. The petiole is short and the apex (leaf tip) ends in a spine.
The flowers are solitary or clustered in lateral cymes (a type of inflorescence), with 1–10 flowers in alternate or opposite axils. The flower colour is mauve, white, cream-coloured, lilac, blue or purple. The corolla (flower petals) is 2-lipped, upper lip 4-lobed, lower lip 1-lobed. The corolla tube is cylindrical.
Each flower is subtended by modified leaves called the calyx lobes. The outer calyx lobes are elliptic, glabrous and with or without the purplish tinge on the veins. The calyx lobe margins are spine-toothed, the apex tapered and ending in a spine. The secondary bracts are called the bracteoles. The bracteole lamina is developed or spinous, with a prominent midrib and margins, with a few scattered teeth, the apex tapered into a sharp point.
The seed capsules are elliptic and tapering to a point. There are 4, hairy seeds per capsule.
According to the Red list of South African plants, Barleria rigida is assessed as Least Concern (LC).
Distribution and habitat
Barleria rigida grows in the arid Kalahari Karroid scrubland in the Northern Cape and Namibia, in deep, sandy soils or in calcrete, gravelly, stony soils.
Derivation of name and historical aspects
The genus name Barleria is derived from the name of a Dominican monk and French botanist, Jacques Barrelier. The species name rigida, means ‘stiff’ or ‘rigid’, referring to the woodiness of the plant. The former variety name ilicina, means ‘like the genus Ilex’ commonly known as holly, referring to the prickly holly-like leaves.
The genus Barleria consists of a large group of shrubs, subshrubs and herbs.
Barleria rigida is pollinated by insects and attracts various species of butterflies.
This species is recommended for rockeries and sunny gardens and tolerates frost and droughts. Barleria rigida flowers in abundance when watering is minimized. Too much water stimulates vegetative growth and less flower production.
Growing Barleria rigida
Barleria rigida can easily be propagated from seeds or cuttings. Harvest the ripe seeds when the capsules turn brown. Use 1 part of washed river sand and 2 parts potting medium, as a growing medium for germination. Place the tray with seeds in a shady spot and water once a week. Germination starts to take place in fourteen days. Transplant the seedlings when 10 cm in size.
Semi-hard plant material is the best for cuttings. Cut the cuttings in lengths of 10 cm.The most effective mixture to root the cuttings in, is 1 part of coarse river sand and 2 parts of potting mix. Good drainage is essential. Treat the cuttings with a rooting hormone. Plant the cuttings 5 cm. apart. Place the container in a shady spot and water twice a week. Transplant the rooted cuttings in a good potting mixture. Expect a success rate of 60%.
There are no specific pests or diseases affecting Barleria rigida.
- Balkwill, M.J. & Balkwill, K. 1998. A preliminary analysis of distribution patterns in a large, pantropical genus, Barleria L.(Acanthaceae). Journal of Biogeography. Vol 5: 95–110.
- Little, J. R. & Jones, C.E. 1980. A dictionary of botany. Van Nostrand Reinhold Compony, New York, Cincinnatti, Toronto, Melbourne.
- Nyirenda, F,C. 2012. Morphological variation in five related species of Barleria (Acanthaceae). Dissertation for Masters of Science, University of the Witwatersrand.
- Raimondo, D. et al. 2009. Red list of South African plants. Strelitzia 25. SANBI (South African National Biodiversity Institute), Pretoria.
Lowveld National Botanical Garden
Plant Type: Shrub
SA Distribution: Free State, Northern Cape
Soil type: Sandy
Flower colour: Blue, Purple, White, Cream, Mauve/Lilac
Aspect: Full Sun
Gardening skill: Easy