Opuntia

The hardiest cactus of eastern North America - a clump-forming, semi-prostrate native that the Missouri Botanical Garden lists at just 6 to 14 inches tall, spreading by flattened, jointed pads that root where they touch ground. Showy bright-yellow flowers 2 to 3 inches across (sometimes with a reddish eye) open in early summer, followed by edible red fruits. In autumn the pads shrivel and lie down as the plant withdraws water for winter; it is thoroughly drought-, dry-soil-, and rabbit-tolerant once established.

A big, tree-like cactus built of flat, oval, jointed pads, grown nearly worldwide for its fruit, the tuna, and its young pads, the nopalitos. The Flora of North America describes a tree of 9.8 to 19.7 feet with yellow to orange flowers and yellow, orange or purple fruits 2 to 4 inches long, and says it is known only from cultivation and from plants that have escaped it, with Mexico its presumed home. Outside USDA zones 8 and warmer it is a container plant for a bright window, sunroom or greenhouse. In warm, dry regions it escapes: the Flora records it naturalized in Arizona and California, and WCVP lists 81 areas worldwide where it has been introduced. Its pads and fruit carry tufts of tiny barbed bristles, called glochids, that lodge in skin, so handle it with thick gloves.