The bloom you can expect depends on which plant you have. One flower of a night-blooming cereus may come from a flat, leaflike stem; another cactus with the same common name grows upright. Look closely at the leaves of your night-blooming cereus first: on the familiar houseplant, those green blades are actually stems.
Night blooming cereus leaves and the plant behind them
The flat-stemmed houseplant is often Epiphyllum oxypetalum, a tropical cactus also called queen of the night. Its broad green growth has wavy edges and may arch over the side of a pot. What gardeners call night blooming cereus leaves are flattened stems, or phylloclades. They carry out the work usually associated with leaves, and flowers arise from points along their edges. North Carolina State Extension describes the plant and its leaflike growth.
Other cacti share the name night-blooming cereus. Some grow in upright, ribbed columns rather than broad, flat segments. A plant label with a botanical name is more useful than the common name alone when choosing a growing spot. For example, Arizona Extension lists the desert cactus Peniocereus greggii as night-blooming cereus; its needs should not simply be copied from a tropical Epiphyllum.
A night blooming cerus grown as a houseplant may have broad, flat stems that arch over its pot. For a night blooming cyrus, check the plant label and stem shape before choosing care, because different cacti share this common name. The rest of this guide concerns E. oxypetalum.
Watch the edges for buds
Look along the mature, flattened growth rather than only at the tips. A bud begins at an edge and develops into an elongated flower tube. As it grows, leave room around the plant so the bud is not pressed against a wall or tangled in neighboring stems. A small change each day is easier to notice if you look from the same side. A cereus bud develops into a flower along these margins.
A cereus flower is large, white and fragrant. It opens at night and normally withers by the following morning. North Carolina State Extension notes that the species typically flowers in late spring to early summer, while houseplants may bloom sporadically. A bud is worth watching, but its presence does not supply a dependable date on the calendar. Each cereus blossom lasts only a short time.
When a bud looks close to opening, check it in the evening as well as during the day. A flashlight lets you see the cereus’s unfolding flowers without having to move the pot. If more than one bud develops, watch each one: they need not all open on the same night. The flowering of a cereus can be brief, but the developing bud gives you time to get ready.
Give mature growth the right light
This cactus comes from a tropical setting, where it can grow on trees or rocks. Indoors, give it bright, indirect light and protect it from harsh afternoon sun. A spot near a bright window with filtered light can work; outdoors in warm weather, provide shelter from strong sun and gradually adjust the plant to its new position. Direct, intense light can scorch the green stems.
The flowers of cereus plants depend on healthy growth over time. A young cutting needs time to establish itself and develop mature growth before you can reasonably expect a display. If a mature plant has never bloomed, look first at its light and general condition. Moving it from a dim corner to a brighter, protected place gives it a more suitable setting; it does not set a flowering date.
Give the leaflike stems of night-blooming cereus a stable support so their arching growth does not tip the pot. Position the leaflike branches of the night-blooming cereus where they can receive filtered light, with air moving around them. Avoid crowding the pot among taller plants that block that light.
Water with the season
Use a pot with drainage holes and a well-draining mix suitable for this tropical, epiphytic cactus. North Carolina State Extension recommends a cactus or succulent mix with added perlite or sand. In spring and summer, water thoroughly, then let the top of the mix dry before watering again. Empty water that collects in the saucer. The aim is a moist growing mix that drains, rather than roots sitting in water.
In fall and winter, growth slows and the plant generally needs less water. Check the mix with a finger instead of following a fixed weekly schedule: a cool room and a warm, bright room can dry at different rates. Overwatering or poor drainage can lead to root rot, so persistent wetness is a reason to reconsider the pot and mix. Healthy roots support future cereus blooms.
Protect the plant from frost. North Carolina State Extension gives a preferred temperature range of 50–80°F for this species. If the pot spends summer outside, bring it indoors before cold weather arrives and give it a bright, sheltered place. The flat leaves of a night-blooming cereus, properly called stems, are worth keeping out of cold drafts too.
What to expect next season
The next season may bring fresh growth before it brings another cereus flower. Keep a note of where the pot spent the summer, how quickly its mix dried, and when you first saw buds. Over time, those observations will tell you more about your own plant than a promised bloom date. Watch the edges of the night-blooming cereus stems as the days lengthen, and let the plant grow at its own pace.