Cereus hildmannianus
| Light | Full sun to bright light; tolerates some shade |
|---|---|
| Water | Moderate in the growing season; allow to dry between waterings, keep dry in winter |
| Soil | Free-draining cactus mix with plenty of grit (see Soil and potting mix) |
| Temperature | Best above freezing; brief light frost tolerated by established plants, roughly USDA zones 9b–11 |
| Propagation | Cuttings (easy) and seed |
| Toxicity | Non-toxic to cats and dogs |
Cereus hildmannianus is a tall, tree-like columnar cactus from southeastern South America, prized for its smooth, blue-green, ribbed stems that carry few or no spines. It is one of the most widely grown ornamental columnar cacti, valued for its fast growth, statuesque form and forgiving nature. For much of the twentieth century it was sold under the misapplied name Cereus peruvianus, and it is still often labelled that way in the trade.
Description
Cereus hildmannianus is a large, branching cactus that becomes tree-like with age, developing a short woody trunk and a candelabra of upright arms. Individual stems are stout and columnar, blue-green to grey-green when young and maturing to a duller green, divided into a small number of prominent, sharp-edged ribs. The areoles are widely spaced and bear few spines — some plants are almost spineless, while others carry short, stiff spines that darken with age.
The flowers are large, funnel-shaped and nocturnal, opening white with greenish or pinkish outer segments on summer nights and closing by the following morning. They are followed by smooth, egg-shaped fruits that ripen red to violet, splitting to reveal juicy white pulp studded with small black seeds. The fruit is edible and pleasant, a trait shared with several relatives in the genus Cereus.
A well-known peculiarity of the species is its tendency to throw monstrose and crested growth, both of which are propagated and sold as ornamental novelties.
Distribution and habitat
The species is native to southeastern South America, ranging across Argentina, Uruguay, Paraguay and southern Brazil. It grows in a variety of open, sunny habitats including grassland, scrub and rocky slopes, often on well-drained soils. Long cultivated far beyond its native range, it has become naturalised in parts of Australia, South Africa and elsewhere, where it can form thickets in warm, dry country.
Cultivation
Cereus hildmannianus is one of the easiest columnar cacti to grow, which accounts for its popularity as a landscape and container plant. Give it full sun to bright light and a free-draining, mostly mineral mix. Water generously through the warm growing season once the soil has dried, then reduce water sharply and keep the plant dry and cool over winter to prevent rot and encourage flowering.
It is faster and more vigorous than many cacti, and in frost-free climates it makes a dramatic outdoor specimen or hedge; established plants tolerate brief, light frost but soft new growth is easily damaged. In containers it will need repotting into progressively larger pots as it gains height, and a stable, heavy pot to counterbalance the tall stems. See Watering for general technique.
Propagation
Propagation is very easy from stem cuttings: sever a length of stem, let the cut surface callus over for a week or more in a dry, shaded spot, then set it in barely moist gritty mix to root. Cuttings root readily in warm weather. The species also grows well from seed, which germinates freely on a warm, humid mineral surface. Because it is vigorous and undemanding, C. hildmannianus is also a popular rootstock for grafting slower or more delicate cacti.
Cultivars
Selected and mutant forms are common in the trade. The monstrose form, with its lumpy, castle-like growth, is sold almost everywhere as an easy beginner plant, and crested (cristate) forms with fan-shaped growing tips are prized by collectors. A spiralis form, whose ribs twist gently around the stem, is also grown as a curiosity. Crested and monstrose plants are usually maintained vegetatively from cuttings so the mutation is preserved.
Common problems
- Rot — the main cause of loss, almost always from overwatering, poor drainage or cold wet conditions; stems soften and discolour, often from the base.
- Corky scarring — cosmetic brown patches from old wounds, sunscald on unacclimatised plants, or wind rub; harmless but permanent.
- Etiolation — too little light produces thin, pale, weakly ribbed growth that leans toward the light.
- Pests — mealybugs (white fluff in the areoles) and scale are the usual offenders; see Pests and diseases.
See also
- Cereus — the genus overview
- Grafting · Soil and potting mix · Watering · Propagation — cuttings · Propagation — seed · Repotting