Kanna is technically known as Sceletium tortuosum. It is a member of the Aizoaceae (the Fig-Marigold or Ice Plant family) which is a family of flowering plants containing 135 genera and about 1900 species. The genus is part of the subfamily of Mesembryanthemoideae. They are commonly known as stone plants or carpet weeds. Species that resemble stones or pebbles are sometimes called Mesembs.
Recognised synonyms are Sceletium compactum L. Bolus, Sceletium framesii L. Bolus and Sceletium joubertii L. Bolus. [Please note: We are dealing predominantly with Sceletium tortuosum here, though some of the products sold on this site are based on hybrids developed from S. tortuosum and S. expansum.]
The genus Sceletium (derived from the Latin Sceletus) was determined by N.E. Brown in 1925, who defined the succulent plant by its characteristic skeletonised leaf venation pattern visible in the dry leaves. On the fleshy, thick leaves little “bladder cells”, also called “idioblasts”, are visible. The flowers of Sceletium tortuosum can be recognised by their threadlike petals that are usually white to yellow, but occasionally pale orange or pink as well. The fruit capsule contains kidney-shaped seeds which are brown to black in colour. Sceletium tortuosum is a creeper plant that reaches up to 15 to 20cm in height and is often found covering the ground in the shade of larger shrubberies
The succulent leaves grow in pairs during the winter. In summertime the leaves die off, thereby skeletonising the lower stem in order to protect the plant from adverse environmental conditions. As a succulent, Kanna is well equipped to deal with scarce water resources. By minimizing evaporation and using an excellent water storage ability, Sceletium tortuosum is able to survive in low rainfall areas.
Plants are climbing or creeping. The slender branches become thick and only slightly woody with age. Water cells are conspicuous on the leaves that have recurved tips and 3 to 5 major veins. The flowers are very shortly pedicellate (almost sessile) and of medium size (20 to 30 mm diameter). Petals are white to pale yellow, pale salmon or pale pink. The calyx has four or five sepals. Fruit are 10 to 15 mm in diameter and open when wet (hygrochastic). The species is readily distinguishable by the imbricate leaves with incurved tips.
Distribution and Climate
Most of the approximately 1000 species of Mesembryanthemoideae are endemic to the arid and semi-arid regions of Southern Africa. Sceletium tortuosum mainly grows in the areas of South Africa known as Namaqualand and Kannaland (where rainfall can be as low as 100ml per year). This region is situated in the Western Cape province in the south of the country. Sceletium is also found in other hot and dry areas of the Western, Eastern and North Cape provinces of South Africa.
Kanna ranges from Namaqualand to Montagu through to Aberdeen and commonly occurs in quartz patches and is usually found growing under shrubs in partial shade. The plants are insect pollinated. Seed dispersal occurs during rain events by means of hygrochastic fruit capsules that open when wet allowing seed to escape.
Detailed Botanical Classification
Species: Sceletium tortuosum
The genus contains 8 currently recognised species from the mostly “weedy” subfamily, Mesembryanthemoideae. These are:
An alternative classification (proposed by Klak et al. 2007) for the Sceletium genus is:
Mesembryanthemum archeri [Sceletium rigidum]
Mesembryanthemum ladismithiense [Sceletium strictum]
In 1986, Bittrich argued for a broader circumscription of Phyllobolus which included Sceletium as one of five subgenera. Since Gerbaulet was unable to find a synapomorphy (a unique derived character) for Bittrich’s broad concept of Phyllobolus, she reinstated Sceletium as a genus (Gerbaulet, 1996).