Queen of the night care guide

A climbing cactus that blooms for one night

Selenicereus grandiflorus comes from Mexico, Central America and the Caribbean. In the wild its long, thin, angled stems, about 2.5 cm (1 in) across and spiny, climb through shrubs, trees and over rocks, holding on with aerial roots. From late spring into high summer a mature plant opens huge white flowers, up to about 30 cm (12 in) across and scented of vanilla. Each flower opens at dusk, is fully open around midnight and has faded by morning.

In English, "queen of the night" and "night-blooming cereus" are also used for Epiphyllum oxypetalum, a different cactus that also flowers at night. This page covers Selenicereus grandiflorus. You can tell them apart by the stems: Selenicereus has round, ribbed, spiny stems that climb, while Epiphyllum oxypetalum has flat, spineless, leaf-like branches. Epiphyllum is a forest cactus and wants bright, filtered light out of strong sun, so its care differs.

Two things decide whether it flowers: plenty of light, water and warmth while it grows, and a cool, dry, bright rest in winter. Its stems grow fast and long, so plan for a frame or trellis from the start.

From spring to autumn, while it grows, it needs plenty of water. Water thoroughly once the surface of the compost feels dry, let the excess drain away and never leave the pot standing in water. Rainwater at room temperature is ideal, since minerals in tap water can build up in the compost.

From about November to early March, keep it almost dry. Water only if the stems start to shrivel. Watering a resting plant in winter encourages weak growth and can stop it from setting buds.

Give it a bright, sunny window. Cacti flower best with as much light as possible all year, and that includes the winter rest, so choose a bright spot for winter too. Too little light is one of the reasons a plant grows but does not flower.

Feed it once a month from about April to September with a liquid feed high in potassium, such as a tomato feed, or a liquid cactus feed. Do not feed it during the winter rest.

Keep it warm while it grows. In winter, give it a rest at about 10 to 14 °C (50⁠–⁠57 °F) in a bright, cool place such as a stairwell window, a conservatory or an unheated bedroom. Avoid long spells well below 10 °C (50 °F). It is not frost hardy. A spot above a radiator in a heated living room spoils the rest and usually means no flowers the next summer.

Ordinary room air is fine. In the growing season it appreciates misting now and then, and warmth with humid air helps it set buds. Keep it dry in winter.