Your plant's health can be determined by its leaves being glossy and succulent. This is how the leaves are transported from their parent to another place, where they become new plants. Although there has been much debate over which species Opuntia Ellisiana it is, most people I know agree with David Furguson's conclusion of Opuntia cacanapa. Some species form clumps while others remain solitary, such as F. acanthodes, F. wislizenii, and F. acanthodes, both in the Mojave Desert and the Sonoran Desert.