Ferocactus macrodiscus aka Candy Cactus

Ferocactus macrodiscus is a low, spiny cactus from Mexico. Its range runs from Tamaulipas south to Oaxaca. It belongs to the cactus family, Cactaceae. Common names include candy cactus and barrel cactus. This evergreen succulent lives for many years. In the wild, it grows in dry grasslands and oak woods. Plants occur in scattered sites rather than across the whole range.

The plant forms one broad stem with a strong taproot. Its blue-green body looks like a flattened ball or disc. It reaches about 0.33 feet [0.10 m] tall. The usual width is 0.98–1.48 feet [0.30–0.45 m]. Some plants reach nearly 1.97 feet [0.60 m] across. Much of the stem can sit below ground level. During drought, it shrinks and sinks deeper into the soil. Rain makes it swell again, which helps reveal hidden plants.

The stem has 16–21 ribs, though counts can vary more widely. Small notches hold areoles lined with yellow felt. Curved spines range from yellow to red. Each areole bears six to eight outer spines. It also has one to four thicker central spines. One longer central spine points down and may show bands. Flowers have pink or purple centres and pale petal edges. Their pale areas can make them look white with coloured stripes. Wild plants bloom from April through July. Bees visit the flowers and act as pollinators. Round red to magenta fruits follow, holding small, dark brown seeds.

Growers use this species as an ornamental pot plant. LLIFLE reports that it can flower in a small greenhouse pot. Plants may bloom when only a few years old. The source gives mixed accounts of seedling growth speed. It recommends rich soil that drains well, near pH 6. It lists seed as the means of propagation. The supplied sources give no firm frost limits or pest guidance.

People gather this cactus from the wild for food. They use the flesh inside the stem to make sweets. They also eat the sour fruit, either fresh or cooked. Useful Tropical Plants lists no known hazards or medicinal uses. That does not establish safety for pets or every use. The same source reports a Vulnerable IUCN listing from 2017. Loss of grassland and oak woods threatens its scattered populations. Farming and cattle grazing drive much of that habitat loss.