Senecio
Senecio is a vast genus in the daisy family (Asteraceae) that includes, among its thousands of mostly non-succulent members, a well-loved group of leaf-succulents grown as houseplants and rockery plants. Many of the succulent species — the trailing "string" plants, the upright blue chalk-sticks and the bead-like String of Pearls — have in recent years been reclassified into the segregate genus Curio, though hobbyists and the trade still overwhelmingly sell and label them as Senecio. This page covers the succulent members of the group as growers encounter them.
Description
Succulent Senecio (and Curio) are extremely varied in form but share a few tell-tale traits. Their leaves are the water-storage organ, ranging from the round, pea-like beads of String of Pearls to the fat blue cylinders of blue chalk-sticks and the flat, arrow-shaped foliage of climbing kinds. Many carry a waxy, powdery-blue glaucous bloom that protects them from strong sun, and several bead-leaved species have a translucent "window" — a clear line or panel down the leaf — that lets light reach chlorophyll deeper inside.
Unlike most cacti and other stem-succulents, these are members of the daisy family, and it shows in the flowers: small brush-like or button heads, often creamy white, yellow or orange, that frequently smell of cinnamon or spice. Growth habits split roughly into trailing/creeping stems that root as they run, and stiff, upright, shrubby forms.
Distribution
The succulent species are concentrated in the drier parts of southern and eastern Africa, with a strong presence in South Africa and Namibia, extending up through East Africa. In habitat they grow among rocks and low scrub, often scrambling under the shelter of shrubs or trailing over rock faces where their shallow roots find fast-draining, gritty ground.
Notable species
- Senecio rowleyanus (Curio rowleyanus) — String of Pearls, spherical beaded leaves on fine trailing stems; the most popular of all.
- Senecio herreianus (Curio herreianus) — String of Tears / String of Beads, larger, more tear-drop leaves with prominent windowing.
- Senecio radicans (Curio radicans) — String of Bananas / String of Fishhooks, vigorous glossy curved leaves, one of the easiest trailers.
- Senecio peregrinus — String of Dolphins, a hybrid whose curved leaves resemble leaping dolphins.
- Senecio serpens (Curio repens) — Blue Chalk-sticks, a low, spreading groundcover of powder-blue finger leaves.
- Senecio mandraliscae (Curio talinoides var. mandraliscae) — a taller blue chalk-sticks widely used as a landscape groundcover.
- Senecio articulatus (Curio articulatus) — Candle Plant / Hot Dog Cactus, jointed sausage-like stems.
- Senecio haworthii — Cocoon Plant, upright stems clothed in dense silvery-white felt.
Cultivation
Most succulent Senecio are forgiving and beginner-friendly, and their chief enemy — as with nearly all succulents — is staying wet. Grow them in a very free-draining, mostly mineral mix and water only once the soil has dried out, watering more generously in the active growing season and easing right off in the plant's rest period. The trailing bead-leaved kinds are shallow-rooted and dislike sitting in a large, soggy pot, so a snug container and restraint with the watering can go a long way. See Watering and Repotting for general technique.
Give them bright light — an hour or two of direct sun and otherwise strong indirect light suits most. Too little light and the trailing stems stretch, the leaves space out and beaded types lose their plump roundness. The glaucous blue-leaved and felted species in particular relish sun and sharp drainage, and resent humidity around the leaves. Nearly all are tender and must be kept above freezing; the blue chalk-sticks are among the hardiest and are used outdoors as groundcover in mild, dry-summer climates.
Propagation
These are some of the easiest succulents to multiply, which is a large part of their popularity. Trailing kinds root almost effortlessly from stem cuttings: a length of stem laid on or lightly pressed into the mix will root from the nodes along its length, and pinning several pieces around a pot quickly fills it out. Upright and shrubby species likewise strike readily from stem cuttings taken in the growing season. Let cut ends callus briefly before potting, and keep the mix barely moist until roots take hold.
Toxicity
It is worth flagging that the popular string-of-pearls group is considered mildly toxic if eaten and can irritate skin, so they are best kept out of reach of curious pets and small children. Many wild Senecio also contain pyrrolizidine alkaloids and are toxic to livestock, though this is more a rangeland than a windowsill concern.
Hobby and cultivar notes
The succulent Senecio have become mainstays of the houseplant and hanging-basket world, sold as much for their whimsical common names as their botany. Variegated forms of String of Pearls and String of Bananas — with cream, pink or white marbling — are especially prized; being lower in chlorophyll they grow more slowly and want a touch more light without scorching. The dolphin-leaved S. peregrinus is a garden hybrid rather than a wild species. Growers should be aware of the ongoing Curio reclassification, as the same plant may appear under either name in catalogues.
See also
- Curio — the segregate genus into which many of these succulents have been moved
- Senecio rowleyanus · Senecio radicans · Senecio serpens
- Soil and potting mix · Watering · Propagation — cuttings · Repotting · Pests and diseases