Senecio serpens
| Light | Bright light to full sun; colours up best with plenty of sun |
|---|---|
| Water | Sparingly; let the mix dry fully between waterings, near-dry in winter |
| Soil | Gritty, free-draining succulent mix (see Soil and potting mix) |
| Temperature | Keep above freezing; USDA zones 9b–11, best around 10–27 °C |
| Propagation | Stem cuttings (very easy); division |
| Toxicity | Toxic if eaten; keep away from pets and children |
Senecio serpens is a low, spreading South African succulent grown for its finger-like, powder-blue leaves, and is one of the most popular "chalksticks" in cultivation. Widely sold as dwarf blue chalksticks, it forms a dense, ground-hugging carpet of upright, waxy blue-grey stems that read almost silver in strong sun. It now sits in the genus Curio, to which many of the shrubby and trailing former Senecio succulents have been moved, and is closely allied to the taller blue chalksticks it is often confused with.
Description
Senecio serpens is a compact, mat-forming succulent that rarely climbs above 20–30 cm tall but creeps outward to form a broad, spreading colony. The stems are soft and semi-prostrate at the base, rooting where they touch the ground, and turn upright at the tips. Each stem is closely set with slender, cylindrical to slightly flattened leaves, gently curved and tapering to a point, in a chalky blue-grey to powder-blue that comes from a waxy farina coating the surface. Rubbed off, this bloom does not return on that leaf, so plants are best handled gently.
In sun the foliage develops its bluest, most silvered tones, sometimes with a faint purplish flush at the tips; in shade it drifts toward plain green. Small, off-white to dull-yellow flowers appear on short stalks in the warmer months. They are the typical little brush-like daisy heads of the family Asteraceae — modest and only lightly fragrant — and most growers value the plant for its foliage rather than its bloom.
Distribution and habitat
The species is native to the Eastern Cape of South Africa, where it grows on dry, rocky slopes and in open, well-drained ground. In these habitats it spreads into low mats among stones and coarse soil, weathering long dry spells on its water-storing leaves and stems. Its natural toughness and its taste for lean, gritty conditions carry directly over into cultivation.
Cultivation
Senecio serpens is an easy, forgiving succulent and an excellent choice for beginners, rock gardens, and dry borders in frost-free climates. Give it a gritty, sharply draining mix and as much light as you can — full sun outdoors, or the brightest spot you have indoors — to keep the leaves compact and richly blue. In too little light the stems stretch and flop and the colour fades.
Water only when the mix has dried right through, then water thoroughly; the plant is far more tolerant of drought than of soggy roots. Ease off almost entirely in winter, when cool, damp conditions are the main cause of rot. It makes a superb, low-maintenance groundcover in mild-winter gardens and spills nicely over the edges of pots and troughs; where frost is a risk, grow it in containers that can be moved under cover. See Watering and Repotting for general technique.
Over time the centre of an old mat can grow bare and leggy. A refresh is simple: cut back hard, replant the best tips, and the colony fills back in quickly.
Propagation
Propagation could hardly be easier. Stem cuttings root readily — take a few centimetres of healthy stem, let the cut end callus for a day or two, then lay or push it into a gritty mix and keep it barely moist until roots take. Pieces that have already rooted along a trailing stem can simply be lifted and divided. The plant is so willing from cuttings that seed is rarely bothered with in the hobby. See Propagation — cuttings and Propagation — offsets for details.
Common problems
- Rot — the usual killer, almost always from overwatering or a slow-draining mix, especially in cool weather; stems go soft, translucent, and mushy at the base.
- Etiolation — too little light stretches the stems, spaces out the leaves, and washes the blue toward green.
- Lost bloom — the powdery blue farina rubs off permanently where handled, leaving green marks; simply avoid touching the leaves you want to stay silvery.
- Pests — mealybugs (white fluff in the leaf axils) and the occasional aphid are the most common; see Pests and diseases.
See also
- Curio — the genus overview
- Senecio mandraliscae — the taller "blue chalksticks", often confused with this species
- Soil and potting mix · Watering · Propagation — cuttings · Propagation — offsets