Scientific: Myrtillocactus geometrizans
Common: Bilberry cactus, whortleberry cactus, blue candle, blue myrtle cactus
Family: Cactaceae
Origin: Tropical deciduous forest, xerophyllous scrub and less frequently in grassland in some areas of the southern Chihuahuan Desert in central Mexico at elevations from 3,000 to 7,000 feet

Pronounciation: Mire-til-lo-CAC-tus gee-o-me-TRY-zans

Hardiness zones:
Sunset 13, 16-17, 21-24
USDA 9 (might occasionally need cold protection)-11

Landscape Use: Strong accent or focal point for xeric landscape themes, rock gardens, large desert estate plantings.

Form & Character: Upright, spreading, blue-gray candelabra like cactus, tree-like, imposing, dominant, arid.

Growth Habit: Evergreen, perennial succulent, moderately upright and highly branched to 15 feet tall (often shorter in Phoenix) with equal to greater spread.

Foliage/texture: Bluish-gray, glaucous stems up to 5-inches thick, stem have 5 to 8 ribs that are approximately 1 inch in depth with areoles that are about 1-inch apart, areoles have 3 to 9 very short spines; coarse texture.

Flowers & fruits: Single, small (1- to 2-inches in diameter), nocturnal greenish creamy-white flowers on stem rib areoles on large mature plants only, flowers last only one day. Fruits are oblong, deep red to blue in color when mature, very sweet, edible, to 1 inch in diameter.

Seasonal color: Flowers in summer and blue fruits in fall and early winter.

Temperature: Hardy to 24oF, otherwise heat tolerant.

Light: Full sun to partial light western shade from desert trees, no shade.

Soil: Gravelly, well-drained mineral soil is best.

Watering: Water occasionally to maintain turgidity, especially in summer.

Pruning: None, except to control width by occasionally thinning out awkward or crossing branches.

Propagation: From softwood stem cuttings allow cut surface to callous over before planting directly into soil. Commonly used as a rootstock for grafting cacti.

Disease and pests: Susceptible to root rot in damp poorly drained soils.

Additional comments: M. geometrizans forma cristatus is a crested variant with real landscape visual interest. In Mexico, the bilberry fruits are of commercial use.