Two plants have the name night blooming cereus. One is the Hylocereus undatus and is the most common, and the other is Selenicereus, whose nickname is queen of the night. The two plants are both from the cactus family and are fast-growing vines. The flowers open only at night and can be up to a foot or more in width. Each bloom will only last for one night. Night blooming cereus is normally grown as house plants, and the fragrance from the large blooms can fill a room. These are not a difficult plant to grow.
Mix 1 part sandy potting soil with 1 part compost and fill a 10-inch container within 2 inches of the top. Plant the night blooming cereus in the center of the container.
Water the plant well so the water drains through the drain holes. Allow the plant to sit for a half-hour and remove the drain tray and discard any water that has come through. Well-draining soil is essential to any type of cactus.
Place the container where the plant will receive plenty of bright light, but not direct sun. A few feet from a window or filtered light is best. The plant can be taken outdoors during the summer months and placed in a partially shaded area for some fresh air.
Water when the top of the soil starts to feel dry during the growing season, spring and summer. During the dormant season of late fall and winter, water when the soil is dry.
Fertilize the plant in spring with a good water-soluble houseplant fertilizer and once every other month during the blooming season, which is normally July through October. Follow manufacturer's directions on the amount to use. Do not fertilize through the winter.
Keep the plant in total darkness from sunset to dawn during the growing season. You will be able to tell when a bloom is about to open and can use back lighting to view it.
Prune back thin stems at the base of the plant when there are too many. Flat stems can be removed at a node to keep the plant from becoming too large.
Cuttings can be placed in the same potting soil and compost mixture to root to make new plants. Keep the cuttings slightly moist. It should root in three to six weeks, but will take two to three years to flower.