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There are a number of species of leaf cactus split across two scientific categories. Pereskia is a collection of around 25 species of cacti that do not resemble other cacti varieties because they have true leaves, though they do have the characteristic spines and flower formation. Epiphyllum is a group containing 19 species of cacti, most of which are commonly referred to as a leaf cactus. This is incorrect, because these plants do not produce true leaves, but their stems tend to be broad and flat, resembling leaves.
Epiphyllum varieties are native to tropical and sub-tropical regions of Central and South America. The leaf cactus species belonging to this group tend to be night-blooming plants, producing brilliant white flowers — such as the popular Epiphyllum phyllanthus — under the cover of darkness. Epiphyllum species are easy to grow and easily maintained, with unusual growth habits, making them a popular choice for cacti enthusiasts and general growers of house plants.
Leaf cactus varieties belonging to the epiphyllum group are epiphytic, meaning that they climb other plants. These plants, if grown as a house plant or a cultivated specimen, will grow around any type of framework provided. Epiphytic leaf cactus species do not take water or nutrients from the host plant, meaning they are not parasitic and do not kill the host. Instead, the leaf cactus and the plant it climbs co-exist. The leaf cactus is able to sustain itself, using water and nutrients trapped by its leaves.
Many hybrid cultivars of epiphyllum varieties have been developed. This offers growers and collectors a wider range of flower color. Many of these hybrids bloom during the day rather than blooming at night, as the true varieties would.
Pereskia species are also native to Central and Southern America. They are unusual among the cactus family, not only for their leaves but because these leaf cactus species are able to tolerate much higher humidity and far larger amounts of water. Leaf cactus species belonging to the pereskia group are usually quick to spread and, if left unchecked, form large, dense clumps. Some species, such as pereskia aculeata and pereskia grandiflora have edible fruits, with leaves that are also edible if cooked first.
The grandiflora species of pereskia leaf cactus has flowers that look like roses, with groupings of very sharp spines; the mature plant reaches 15 feet (5 m) tall. Pereskia aculeata is a vining shrub native to Brazil and widely cultivated throughout the world as an attractive ornamental. It is particularly quick to spread and is considered an invasive species in both Australia and South Africa.