Opuntia monacantha is a cactus native to Brazil Northeast, Brazil South, Brazil Southeast, Paraguay, Uruguay. It is found growing along the coast but scarcer inland, and is often found on sand dunes in restinga (sandy coastal areas), opencarrasco (upland dry forest plateaus) and in southern humid and subhumid forests. Where introduced, it is also found on coastland, in coastal scrub, moist savanna, agricultural areas and ruderal and disturbed sites. It is found on sandy beaches and cliffs in New Zealand, on seashores and slopes in China from sea level to 2000 m, and in Fiji on dry sites, often in agricultural areas or on waste land near sea level. In South Africa it invaded primarily the south and eastern coastal areas.
In cultivation Opuntia monacantha is perhaps best known in the form of its variety variegata: Opuntia monacantha f. monstruosa variegata. It is commonly known as Joseph's Coat is one of the very few naturally occurring white-variegated cacti. It is variegated or marbled with white, creamy-white, yellow, green and sometimes also with pink in varying patterns.
Opuntia monacantha prefers a lot of light. Mature plants can tolerate heavy sun exposure and hot temperatures during the peak season. In the cooler months and winter, they are just fine indoors with bright indirect light from a window. Immature plants (under two years old) do well with lots of bright, indirect sunlight.
Water thoroughly only when soil has been completely dry for a few days.