Ferocactus (Fe-ro-cac-tus) is a genus of globose ribbed cacti frequently referred to as barrel cacti. Ferocactus is a name that literally translates to "fierce thistle" which is made appropriate by the intimidating size and menacing spines these plants possess.
Form: These plants are usually large and round but some exceptions remain small and manageable. A few even form clumps.
Colors: Most are green in color but a few are blue. The spines can vary dramatically in their color, even on the same plant.
Foliage: All foliage in this genus is organized into spines. There are no photosynthetic leaves.
Flowers: They tend to form a ring around the top of the plant and are either yellow or red. When they're pollinated, they form lemon yellow fruits and keep the dried petals even when they're ripe. This gives them the appearance of pineapples.
Light: Full sun conditions are best and encourage healthy growth and flowering.
Soil: Pick a gritty, well-draining mix like a cactus and succulent soil (available at garden centers) or mix your own (more info).
Water: Water deeply enough for water to run out the container’s drainage hole. Allow soil to completely dry before watering again. Keep dry in winter.
Hardiness:Ferocactus are not frost hardy and should be brought indoors to a sunny window sill if there is a chance of frost. (What’s my zone?)
Propagation: Most of these don't produce offsets and the ones that do produce them very slowly. Therefore, the best way to propagate this is via seed.
NOTES FROM THE NURSERY
Many of these plants are seen in drawings and cartoons that feature desert scenes. A common myth about these plants is that they contain a fresh reservoir of drinking water inside of them for the parched traveler. The truth is, due to the alkalinity of these plants, drinking water from them may make you even more thirsty. Look for flattened Opuntia pads instead as these have more drinkable water in them.
It's important to note also that "barrel cactus" is not a unified group. Many Echinocereus plants also take on that common name. Some Ferocactus even break the mold and have more narrow stems that offset more frequently, like Ferocactus flavovirens.