Myrtillocactus is a genus of cacti found from Mexico to Guatemala. The genus is best known with Myrtillocactus geometrizans. The largest plants in this genus can grow up to 16.5 feet (5 m) tall. Myrtillocactus tends to flower in the summer. After the greenish white flowers, this cactus will produce blue berries, hence the nickname Blueberry Cactus, which are eaten as a snack in Mexico.

Growing Conditions and General Care
In the summer place Myrtillocactus in the sunshine (indoors or outdoors). In the winter find a cooler, light spot. That will allow it to go into next spring well-rested, which will make it more likely to flower.

This easy-care plant doesn’t want a lot of water. Allow the soil to dry out before you give it another drink. Keep the soil completely dry in winter. Need a well-drained soil mix with small gravel added to ensure drainage.

Treat it to special cactus food once a month in the spring and summer.

Source: World of Succulents

Endemic to Mexico.

Scientific classification

Kingdom: Plantae
(unranked): Angiosperms
(unranked): Eudicots
(unranked): Core eudicots
Order: Caryophyllales
Family: Cactaceae
Subfamily: Cactoideae
Tribe: Pachycereeae
Genus: Myrtillocactus
Species: M. geometrizans

                         – Wikipedia.