Nananthus
Nananthus is a small South African genus of tuberous-rooted mesembs in the ice-plant family Aizoaceae, closely allied to Aloinopsis. Its members form low rosettes of narrow, roughly tubercled leaves rising from a swollen, caudex-like taproot, and produce cheerful yellow flowers whose petals are often marked with fine reddish or brownish stripes down the back. Compact, slow and characterful, they are prized by growers of miniature "living-stone" relatives and Karoo caudiciforms alike.
Description
Plants in Nananthus are dwarf, clump-forming succulents that grow from a thick, woody, tuberous root far larger than the visible top. Above ground each head is a small rosette of stiff, upward-pointing leaves — typically narrow and somewhat triangular or keeled in cross-section, with a rough, warty (tubercled) surface and a firm, greyish-green to bronzy colour that deepens under strong light. Over time a plant slowly offsets into a low cushion of several heads.
The flowers are daisy-like in the mesemb fashion (they are not true daisies, but many-petalled succulent blooms) and open in response to sun during the day. Most species are yellow, frequently with a darker central stripe running along the outside of each petal, giving the half-open flower a neatly pinstriped look. Bloom size is modest but generous relative to the small rosettes.
The tuberous root is the genus's signature feature. In habitat it sits mostly buried, storing water and pulling the plant down during drought; in cultivation many growers gradually raise it to display the swollen caudex, giving these plants appeal as miniature caudiciforms.
Distribution
Nananthus is native to the interior of South Africa, chiefly the arid Karoo and Highveld regions and neighbouring dry grassland and scrub, with its range just reaching into adjacent Botswana and eastern Namibia. Plants grow among rock and gritty, well-drained ground, often wedged into crevices or partly hidden in stony soil where the tuber is protected from heat and browsing. The climate is one of bright light, low and seasonal rainfall, and pronounced dry rest periods — conditions the plants are built to survive by retreating into their roots.
The genus sits within a closely related complex of Karoo mesembs, and its boundaries with Aloinopsis (and related genera) have long been debated; some species have been shuffled between the two, which is why older labels and lists treat parts of Aloinopsis and Nananthus as more or less interchangeable.
Notable species
- Nananthus aloides — a widely grown species with rough, aloe-like tubercled leaves and striped yellow flowers.
- Nananthus vittatus — noted for the distinct dark striping ("vittatus" = banded) on its yellow petals; the Highveld plants long listed as Nananthus transvaalensis are now referred here as a synonym.
Because the genus has been repeatedly re-circumscribed, several plants are also encountered under Aloinopsis, and names should be treated with some flexibility.
Cultivation
Nananthus are among the more forgiving tuberous mesembs, but they still reward a dry, mineral regime. Grow them in a very free-draining, mostly grit-based mix in a deep pot that gives the tuber room to develop. Give bright light — full sun in cooler climates, with only light shade from the fiercest summer heat — to keep the rosettes tight and coloured; too little light causes soft, stretched growth.
Water thoroughly during the active growing seasons (cooler spring and autumn for many plants) and let the mix dry out completely between drinks. Ease right off in the heat of high summer and again in cold winter, keeping the plant dry and cool during its rest; the tuber will sustain it. Overwatering a dormant plant, or a slow-draining mix, is the main cause of rot. Protect from hard freezes; kept dry, established plants tolerate light frost, but keep them frost-free and airy to be safe. See Watering and Repotting for general technique.
To display the caudex, pot young plants deep, then raise the tuber a little at each repotting once it has bulked up, letting the newly exposed portion firm up in good light.
Hobby and cultivar notes
Nananthus has little in the way of named cultivars; the appeal lies in well-grown wild forms and the sculptural, gradually exposed tuber rather than in selected colour breaks. Collectors often grow them alongside Aloinopsis, Titanopsis and other Karoo mesembs, and they make excellent subjects for shallow-crevice bowls and miniature caudiciform displays. They are easy to raise from seed and can also be divided.
Propagation
Seed is the usual method: sow on a gritty, mineral surface, keep warm and lightly humid until germination, then grow on hard and bright. Established clumps can also be lifted and divided, and rooted-down divisions or offsets will re-establish on their own tubers. See Propagation — seed and Propagation — offsets for details.
See also
- Aloinopsis — the closely allied genus
- Aizoaceae — the ice-plant family
- Soil and potting mix · Watering · Repotting · Propagation — seed · Propagation — offsets · Pests and diseases