Opuntia cochenillifera
| Light | Bright light to full sun |
|---|---|
| Water | Moderate in growth; dry out between waterings, keep drier in winter |
| Soil | Free-draining gritty mix (see Soil and potting mix) |
| Temperature | Keep above freezing; roughly USDA zones 9–11 |
| Propagation | Pad cuttings (very easy); also seed |
| Toxicity | Non-toxic to cats and dogs, though the tiny bristles can irritate |
Opuntia cochenillifera is a tall, nearly spineless prickly pear of Mexican origin, long grown as the favoured host plant for the cochineal insect (Dactylopius coccus), from which the historic crimson dye carmine is made. Its smooth, flattened green pads and shrubby-to-tree-like habit have earned it the common names cochineal cactus and nopal cochinilla; it is sometimes still placed in the segregate genus Nopalea.
Description
Opuntia cochenillifera grows into a large shrub or small tree, in time reaching a few metres tall with a distinct woody trunk. The flattened stem segments (pads, or cladodes) are elongated to oval, bright to grey-green, and notably smooth: mature plants are essentially spineless, bearing only small tufts of fine, easily detached bristles (glochids) at the areoles. As with all opuntias these glochids are the real nuisance to handle, lodging in skin far more readily than any spine.
The flowers are small and often do not open widely, with pinkish-red to red petals and long, protruding stamens and style — a look typical of the Nopalea group and different from the broad, cupped yellow blooms of many other prickly pears. Flowers are followed by fleshy reddish fruits.
Distribution and habitat
The species is native to Mexico, though centuries of cultivation have obscured its precise wild origin. It grows in warm, seasonally dry scrub and thorn forest. Owing to centuries of cultivation for the cochineal dye trade, it has been carried far beyond its original range and is now naturalised in parts of Central America, the Caribbean, South America, Africa, southern Asia and Australia, where it persists around old plantings and settlements.
Cultivation
This is one of the easier opuntias to keep and a forgiving beginner's cactus. Give it a bright spot — full sun suits it best and keeps the pads firm and compact — and a free-draining, gritty mix. Water moderately through the warm growing season, letting the mix dry out between waterings, and keep it much drier and frost-free over winter. It tolerates a little neglect but resents cold, wet roots, which invite rot.
Grown in a pot it stays manageable for years; planted out in a suitable climate it can become a substantial shrub, so allow room. Handle with care despite the lack of spines: the glochids come away at the lightest touch. See Watering and Repotting for general technique.
Propagation
Propagation is very easy from pad cuttings. Detach a healthy pad, let the cut surface callus over for several days to a week in a dry, shaded spot, then set it upright in barely moist gritty mix; roots form readily in warmth. Seed is also possible but slower and rarely necessary. See Propagation — cuttings for the full method.
Cultivation for cochineal
The plant's fame rests on its role as host for the cochineal scale insect, Dactylopius coccus, which feeds on the pads and yields carmine, a brilliant crimson dye prized since pre-Columbian Mesoamerica and later a major colonial export. Historically, plantations of this and related opuntias were maintained specifically to farm the insects on the pads. Growers today should note the flip side: an unwanted infestation of cochineal or other scale looks like white, waxy, cottony patches on the pads and is treated as a pest (see below).
Common problems
- Rot — from overwatering or cold, wet compost; pads soften, discolour and collapse. Keep dry in winter and in a very free-draining mix.
- Scale and cochineal — white, waxy or cottony tufts on the pads that crush to a red smear; wipe or wash off and treat as for scale insects.
- Glochid irritation — the fine bristles detach at a touch and are hard to remove from skin; handle with thick gloves or folded paper.
- Etiolation — too little light makes new pads thin, pale and stretched.
See also
- Opuntia — the genus overview
- Propagation — cuttings · Soil and potting mix · Watering · Pests and diseases