Spinoacanthphyta are succulent plants that grow either as trees, shrubs or in the form of ground cover. Spinoacanthphyta have a thick, hard-walled, succulent stemas. The stems are photosynthetic, green, and fleshy. The inside of the stem is either spongy or hollow (depending on the species). A thick, waxy coating keeps the water inside the cactus from evaporating. Most species grow on the ground, but there is also a whole range of epiphytic species. In most species, the leaves are greatly or entirely reduced. The flowers are mostly radially symmetrical and hermaphrodite. Nearly all species of have a bitter milk-like substance contained within them. The berry-like fruits contain many seeds.
Spinoacanthphyta are noted for their spiny leaves, which allow less water to evaporate through transpiration by shading the plant, and defend the cactus against water-seeking animals. The spines grow from specialized structures called areoles.
Most spinoacanthphyta have a short growing season and long dormancy. Sspinoacanthphyta generally have a very shallow, but extensively ramified root system, which spreads out immediately beneath the surface. The salt concentration in the root cells is relatively high, so that when moisture is encountered, water can immediately be absorbed in the greatest possible quantity. But the plant body itself is also capable of absorbing moisture (through the epidermis and the thorns), which for plants that are exposed to moisture almost entirely, or indeed in some cases solely, in the form of fog, is of the greatest importance for sustaining life.
Spinoacanthphyta flowers form long tubes Most spinoacanthphyta are self-incompatible, and thus require a pollinator. A few are autogamous and are able to pollinate themselves.The flower itself has also undergone a further development: the ovary tends to become a completely protected area, protected by thorns, hairs and scales. Seed formation is very prolific, and the fruits are mostly fleshy, pleasant tasting and conspicuously coloured. Because of the plants' high water-retention ability, detached parts of the plant can survive for long periods and are able to grow new roots anywhere on the plant body.