Mammillaria mercadensis

Mammillaria mercadensis comes from northern and western Mexico. It belongs to the cactus family, Cactaceae. Kew calls it a succulent subshrub of deserts or dry shrubland. Useful Tropical Plants also places it on rocks in oak woods. Thus, its known sites include both dry land and woods. It grows at heights of about 3,940–8,530 feet [1,200–2,600 metres] above sea level.

This spiny plant stays green and lives for more than one year. It forms one or more stems. Useful Tropical Plants says its form is like a cylinder. Each stem may look like a flat or rounded ball. Stems can reach about 0.26 feet [0.08 metres] across. That width is for one stem, not the whole plant. The supplied account gives no sound height for a full-grown plant. Nor does it say how many spines this species has. It gives no spine colours for this species either.

The small, green fruits have a reddish tint. Most fruits have a shape like a club. The species account says nothing about its flowers or bloom time. It lists the plant as both wild-growing and grown for show. People also gather wild plants for use in local medicine. The source does not say which health problems people treat. Nor does it say how they prepare it or how much they use. This record of use does not prove a health benefit.

In gardens, this cactus needs a dry climate. It needs plenty of warmth while it grows. Useful Tropical Plants says it can bear some brief cold spells. In the wild, it can stand short drops to about −2°C. This tells us about its wild sites, not full garden hardiness. The supplied species facts give no firm light or watering plan. They name no pests or diseases that harm this species.

Useful Tropical Plants reports the IUCN's 2017 rating of Vulnerable. Taking wild plants for medicine and show puts them at risk. Clearing land for agave crops also strips away their habitat. The account reports at least 30% habitat loss over ten years. It links this loss to large farms. The source lists no known hazards but gives no specific tests for toxic effects. It also says no direct proof shows that the fruit is safe to eat. Broad claims about other species in the genus cannot prove food safety here.