Ferocactus is a genus of large barrel-shaped cacti, mostly with large spines and small flowers. There are about 30 species included in the genus. This member of the Cactaceae family is found in the south-western United States and north-western Mexico. The young specimens are columnar but as they grow older ribs form, and they take on a barrel form. Most of the species are solitary but some, such as Ferocactus robustus and Ferocactus glaucescens, form clumps. The flowers are pink, yellow, red or purple depending on the species, and the petals sometimes have a stripe of a darker colour. They are desert dwellers and can cope with some frost and intense heat. The typical habitat is hot and very arid, and the plants have adapted to exploit water movement to concentrate their biomass in areas where water is likely to be present. Like Sclerocactus, Ferocactus typically grow in areas where water flows irregularly or depressions where water can accumulate for short periods of time. They are most often found growing along arroyos (washes) where their seeds have been subjected to scarification due to water movement, but they oddly also tend to grow along ridges in spots where depressions have formed and can hold water for some period. Ferocactus have very shallow root systems and are easily uprooted during flash floods. The “fishhook” spines and the armoured web of spines enclosing the cactus body in many species of this genus are adaptations which allow the plant to move to more favourable locations. In cultivation Ferocactus require full sun, little water, and good drainage. They are popular as indoor houseplants. They are well suited for growing in pots and rockeries. Propagation is usually from seeds as most do not produce off-sets.

Ferocactus wislizeni, the Fishhook Barrel Cactus, also called Arizona Barrel Cactus, Candy Barrel Cactus and Southwestern Barrel Cactus, is native to northern Mexico and the southern United States. It is a ball-shaped cactus eventually growing to a cylindrical shape, with spiny ribs and red or yellow flowers in summer. Some sources mistakenly spell the epithet “wislizenii.” The fishhook barrel cactus typically grows to a diameter of roughly 70cm and a height of 90cm to 180cm. However, specimens as wide as 90cm and tall as 300cm have been recorded. The common name comes from the spines, which are thick and hooked. It has a leathery asparagus green cortex (skin) with approximately 15-28 ribs per cactus. Its flowers are yellow to red-orange and appear atop the cactus fruit during the summer months. The fruits are green when unripe, yellow after the flower dries up, and persist atop the cactus long after the flower is gone, sometimes for more than a year. In adulthood, fishhook barrel cacti generally lean southward, toward the sun, earning them the nickname “compass barrel cactus.” One theory about why this happens is, the afternoon sun is so intense it slows the growth on the exposed side, causing the plant to grow unevenly. Older barrels can lean so far, they uproot themselves and fall over, especially after heavy rains when the soil is loose. Its life cycle is 50–100 years.