Several characteristics are common to all cacti. For example, they all have a succulent stem. Most cacti, except for the Pereskia genus, lack an inferior ovary. Cacti have areoles, which consist of two perpendicular buds. Flowers, fruit or new branches grow from the upper bud of a cactus, while spines grow from a lower bud. Their large showy flowers are usually solitary and come in colours including reds, oranges, pinks and yellows.
Barrel cacti, which are named for their barrel shapes, have prominent ribs and heavy spines. Flowers always grow on the top, and they only have a few scales. This cactus has fleshy fruits, although it isn't usually edible. Some species have spines curved like a fishhook, such as the fishhook barrel cactus. Another species, the candy barrel cactus, receives its name from the cactus pulp it produces, which is used in making cactus candy.
Columnar cacti have cylindrical stems with ribs that run from bottom to top. They're at least ten times taller than they are wide, according to Pima College. Most of these cacti are large and have white but somewhat reddish large flowers that are nocturnal. Its fruit is rather large, oblong and hairless. One of the most common species is the saguaro cactus, which has green flowers and coarse foliage. Other columnar cacti include species such as the senita, cardon and organpipe cactus.
Hedgehog cacti lack leaves, have sharp spines and are usually less than 12 inches tall, notes the Northside Independent School District. Flowers grow from the sides of their stems, The hedgehog cactus produces cup-shaped, scarlet red flowers containing many petals. Flowers remain open at night, lasting three to five days and its red fruit is edible. This cactus grows on extremely high mountains and is found in various regions of the Southwest.
Prickly pears have many flattened branches, called pads, that resemble fleshy, overgrown leaves. These woody, succulent cacti have spiny stems and grow up to 1.5 feet tall, says the University of Florida. Their unnoticeable leaves are covered with tiny, spiny hairs and their yellow, showy flowers contain numerous short spines and petals in the centre. The plant's reddish-purple fruit, which is somewhat sweet, is a round berry containing many flat seeds.