Othonna
Othonna is a large genus of succulent and semi-succulent plants in the daisy family (Asteraceae), native mostly to southern Africa. It is a wonderfully varied group for growers: it spans low, trailing groundcovers grown for their bead-like leaves down to prized winter-growing caudiciform species that swell into gnarled, bonsai-like stembases beloved by collectors of fat-plants. Nearly all bear small, typically yellow daisy flowers on slender stalks.
Description
Othonna is united by the daisy-family flowerhead — a small capitulum carrying ray and disc florets, most often bright yellow, though some species flower in white, pink or mauve. Beyond the flowers the genus is remarkably diverse in form. Many species store water in swollen leaves that may be cylindrical, club-shaped, paddle-like or almost spherical, giving a fleshy, glaucous appearance. Others invest their reserves below the neck, forming a woody or corky caudex — a fattened, often above-ground stembase — from which thin deciduous branches and leaves emerge each growing season.
Habit ranges accordingly from creeping mat-formers and pendent trailers to dwarf shrublets and stout caudiciform miniatures. This structural variety, combined with generally undemanding care, is a large part of the genus's appeal.
Distribution
The great majority of Othonna species are concentrated in the winter-rainfall regions of South Africa and Namibia, especially the arid Namaqualand and Karoo, with a scatter of species elsewhere in southern Africa. Species from the winter-rainfall zone are typically winter growers: they leaf out and flower during the cool, moist months and drop their leaves to rest through the hot, dry summer. A grower's watering calendar should follow the plant's origin rather than the local season.
Notable species
- Othonna capensis — the popular "Ruby Necklace" trailer, grown for its slender bead-like leaves that blush purple-red in bright light; an easy, fast groundcover and hanging-basket plant. Note that this species has since been transferred to the segregate genus Crassothonna (accepted name Crassothonna capensis), though it is still almost universally sold and grown under the older name Othonna capensis.
- Othonna clavifolia — a compact species with densely clustered club-shaped leaves.
- Othonna euphorbioides — a spiny-looking caudiciform shrublet with a stout base, popular with caudex collectors.
- Othonna herrei — prized for its knobbly, warty caudex and curled leaves, a classic "fat plant" for specialist collections.
- Othonna retrofracta — a caudiciform species with fine, deciduous foliage over a swollen base.
- Othonna cacalioides — a dwarf, highly succulent species from Namaqualand favoured by miniature-caudex enthusiasts.
Cultivation
Most Othonna are straightforward if you respect their growth cycle. Grow them in a very free-draining, mostly mineral mix in a pot that drains freely, in bright light — good light keeps trailing species compact and brings out the ruby tones in O. capensis. See Watering for general technique.
The key to the winter-growing species is seasonal watering: water regularly while the plant is in leaf and actively growing (autumn through spring for winter growers), then ease off and keep it nearly dry during its summer dormancy, when the leaves naturally drop. Watering a resting caudiciform Othonna is the quickest way to rot it. Protect plants from frost and give the caudex forms a snug pot; many collectors gradually lift the caudex above the soil line over successive repottings to show off its shape.
The easier trailing species such as O. capensis are forgiving, tolerating more water and warmth than their choosy caudiciform relatives, which makes them a good entry point to the genus.
Propagation
Trailing and shrubby species root very easily from stem cuttings taken in the growing season — O. capensis in particular strikes readily from short pieces laid on or pushed into the mix. Caudiciform species are usually raised from seed, as they resent losing branches and are slow to build a caudex; sow onto a gritty surface and grow the seedlings on patiently. See Propagation for an overview.
Hobby and collector notes
Within the hobby, Othonna really has two audiences. The trailing "string" types — above all "Ruby Necklace" (O. capensis, now placed in Crassothonna) — are grown as ornamental groundcovers and hanging plants, valued for fast growth and colourful foliage. The caudiciform species, by contrast, are collector's plants: slow, sculptural and often traded as prized specimens among fans of caudex and "fat" plants. Named seed-grown forms and selections circulate, but the genus is grown far more for natural form and the character of the caudex than for cultivars.
See also
- Caudex — swollen stembases in succulents
- Asteraceae — the daisy family
- Soil and potting mix · Watering · Repotting
- Propagation — cuttings · Propagation — seed