Cereus jamacaru
| Light | Full sun to bright light |
|---|---|
| Water | Moderate in the warm season, letting the mix dry between waterings; keep dry and cool in winter |
| Soil | Fast-draining but reasonably rich mineral mix (see Soil and potting mix) |
| Temperature | Best kept above freezing; tolerates brief light frost when dry (roughly USDA zones 9b–11) |
| Propagation | Seed and stem cuttings |
| Toxicity | Not known to be toxic to cats and dogs |
Cereus jamacaru is a large, tree-like columnar cactus native to eastern Brazil, where it is widely known as the mandacaru. It is one of the signature plants of the caatinga, the semi-arid thornscrub of the Brazilian sertão, and its tall, candelabra-branched silhouette is a familiar landmark of that landscape. Fast-growing, hardy and easy to please, it is also widely grown as an ornamental and as a robust rootstock for grafting.
Description
Cereus jamacaru is a genuinely tree-like cactus, in time developing a distinct woody trunk from which numerous branches rise in a broad, candelabra-like crown. Mature plants can become several metres tall. The branches are stout, blue-green to grey-green when young, and divided into a handful of prominent ribs running the length of the stem. Woolly areoles sit along the rib margins, each bearing a cluster of stiff, needle-like spines that vary in length and colour between plants.
Like most of the genus, it is night-blooming. Large funnel-shaped flowers open after dark in the warm months, white within and greenish to brownish on the outside, and close by the following morning. Pollinated flowers are followed by fleshy fruit that ripen red or pink and split to reveal white pulp studded with small black seeds — edible, and eaten locally as well as taken by birds.
Distribution and habitat
The mandacaru is native to eastern Brazil, most abundant across the semi-arid northeast, where it is a characteristic component of the caatinga and associated dry woodland and rocky terrain across the interior of the sertão. It thrives in hot, seasonally arid conditions, storing water in its thick stems to carry it through the long dry season. In cultivation it has spread far beyond its native range and is grown in warm, dry gardens in many parts of the world.
In its homeland the plant carries considerable cultural weight: it is a byword for endurance in the harsh backlands, is planted as a living fence, and its chopped stems, with the spines burned or cut off, have traditionally been used as emergency fodder for livestock during drought.
Cultivation
Cereus jamacaru is one of the easier columnar cacti to grow, forgiving of the mistakes that would kill fussier species. Give it as much sun as you can and a free-draining mineral mix; unlike many desert cacti it will reward a somewhat richer soil and regular water during the growing season with vigorous growth. Water thoroughly when the mix has dried, then let it approach dryness again. Reduce watering sharply in winter and keep the plant cool and dry, which both hardens it against cold and encourages flowering.
Young plants are fast and may need staking until the trunk firms up, and a large specimen will eventually want a heavy pot or a spot in the open ground. See Watering and Repotting for general technique. The species' vigour also makes it a popular, sturdy grafting stock for slower or more delicate cacti.
Propagation
Both seed and cuttings work well. Seed germinates readily on a warm, humid mineral surface and seedlings grow quickly (see Propagation — seed). Large stem sections root easily as cuttings: take a branch, let the cut surface callus for a week or two in a dry, shaded spot, then set it in barely moist gritty mix until roots form. Cuttings are the quickest way to a large plant and to reproduce a particular form.
Common problems
- Rot — from cold-wet conditions or a waterlogged mix, usually starting at the base; keep the plant dry through winter.
- Etiolation — too little light produces thin, pale, weak growth instead of stout blue-green stems.
- Corky scarring — cosmetic brown patches from old damage or sunburn on plants moved abruptly into full sun; harmless but permanent.
- Pests — mealybugs in the areoles and scale on the stems are the usual offenders (see Pests and diseases).
See also
- Cereus — the genus overview
- Grafting · Soil and potting mix · Watering · Propagation — cuttings · Propagation — seed