Evergreen cacti originating in Mexico, widespread in most of the globe, especially in Astralia and in the Mediterranean basin, Opuntias have erect or slightly prostrate stems, divided into large, oval, flattened segments, with a diameter of 30-70 cm, fleshy , of a bright green color, generally called pale; they have few sharp spines, grouped in groups of 2-3, 4-5 cm long; adult plants can reach 4-5 m in height.
From late spring to summer the plant produces numerous cup-shaped flowers, yellow or orange, arranged on the edges of the blades; the flowers are succeeded by the fruits, oval, 10-15 cm long, fleshy, thorny, green, turning purple red when ripe. The whole plant is edible, the blades generally cook, while the fruits are eaten raw, after having deprived them of the thick prickly rind.
The prickly pear (Opuntia ficus-indica) is a shrub that can reach 3.5 meters in height and width. It has a very particular and recognizable shape: the stems are in fact flat and wide and are commonly called shovels, even if their real scientific name is cladodes.
Their surface is mostly smooth, glaucous green in color, but dotted with cushions (the areolas) from where waxed spines depart. Next to it there are other smaller ones, at least a few millimeters long, which have the purpose of retaining the environmental humidity. Particular attention must be paid to them because they detach easily, sticking deep into the skin. They are in fact also a means of defense.
The opuntie constitute one of the most consistent groups within the Cactaceae: up to 300 species have been classified. They mostly come from areas characterized by strong aridity. This does not mean, however, that they cannot be resistant to low temperatures. In the American continent (where they find their origin) in the spontaneous state they can even be found in mountainous areas, in particular in the Andes they have adapted to survival even above 5000 meters of altitude. We also keep in mind that even in a desert environment, resistance to cold is a very important feature. There are in fact environments in which the temperature range between night and day is of considerable size.