Cereus forbesii 'Spiralis'
Cereus forbesii 'Spiralis is a striking cultivated form of the columnar cactus Cereus forbesii in which the ribs twist in a regular helix around the stem, spiralling up the column as it grows. This corkscrew habit makes it one of the most instantly recognisable and sought-after collector cacti, often traded under the older name Cereus peruvianus 'Spiralis'. Care follows that of the parent species.
Description
'Spiralis' shares the blue-green, sculptural columns of ordinary Cereus forbesii, but its ribs — instead of running straight up the stem — wind around it in a smooth, twisting spiral. The effect is most pronounced on established, well-grown plants, where the whole column appears to corkscrew as it climbs. Spines sit along the raised rib edges, following the same helical path.
Young seedlings often begin fairly straight and develop the characteristic twist as they grow, and the tightness and regularity of the spiral varies from plant to plant. Like the parent species, mature specimens branch with age and can produce large, nocturnal white flowers followed by edible fruit, though most collectors grow 'Spiralis' for its form rather than its blooms.
Cultivation
Grow 'Spiralis' exactly as for the parent species — see Cereus for full detail. It is one of the easier columnar cacti: give it bright light, a fast-draining, mostly mineral mix, and water generously through the warm months once the soil has dried, tapering off to a dry rest in winter. It is fast-growing and forgiving by cactus standards, tolerating more water than most globular species while in active growth.
Strong, direct light helps keep the twist tight and the column firm; in too little light the stem etiolates, growing pale, thin and less sharply spiralled. Because plants become tall and top-heavy, a generous pot and the occasional stake help keep them upright. See Watering and Repotting for general technique.
Propagation
'Spiralis' is usually increased from stem cuttings, which root readily once the cut surface has callused for a week or two on dry, warm substrate. Cuttings reliably carry the spiralled trait. The cultivar can also be raised from seed, though seedlings vary in how strongly and how soon they twist, so vegetative propagation is preferred where a guaranteed spiral is wanted. Its vigour also makes it a popular, easily grown grafting stock for slower or more delicate cacti.
See also
- Cereus — the parent species and genus
- Grafting · Soil and potting mix · Watering · Propagation — cuttings