Epiphyllums are tropical cacti native to South and Central America. Also called orchid cactus, they are prized for their night-blooming white, yellow, or more rarely, red flowers. Unlike desert cacti, tropical epiphyllums don't have long spikes or needles, though they do have sharp hairs along their branches. Grow them as houseplants, as epiphyllums thrive in temperatures around 70 degrees F and don't tolerate cold. Fertilization ensures the cactus blooms well and remains healthy. Fertilize it from spring until it enters dormancy in late fall.
Start fertilization in early spring when the epiphyllum begins putting on new growth. Fertilize once monthly during spring and summer.
Fill a shallow bowl that is larger than the plant's pot base with lukewarm water. Add a half-strength solution of 6-25-25 fertilizer to the water. This is 6 parts nitrogen to 25 parts of phosphate and potash.
Set the pot in the bowl of fertilized water for two to three hours. The soil in the pot will draw the fertilized water up to where the roots benefit from the treatment. Top dressings of fertilizer run out the drainage holes before the epiphyllum absorbs it.
Fertilize with a half-strength 20-20-20 fertilizer—equal parts nitrogen, phosphate and potash—monthly in midsummer after the cactus quits blooming. Continue this treatment until the plant enters dormancy, usually in November.