Scientific: Pachycereus marginatus (synonyms: Lemaireocereus marginatus, Marginatocereus marginatus, and Stenocereus marginatus)
Common: Mexican organ pipe cactus
Family: Cactaceae
Origin: Oaxaca in central Mexico

Pronounciation: Pack-a-SER-e-us mar-gi-NA-tus

Hardiness zones
USDA 9 (in urban areas only because of the urban heat island effect), 10-11

Landscape Use: Specimen or focal point in the landscape, desert landscape design themes, similar to Organ Pipe cactus (Stenocereus thurberi), but with a cleaner, sleeker, more friendly appearance.

Form & Character: Upright, stiff and visually imposing, smooth and columnar, majestic.

Growth Habit: Slow and strongly upright to 25 feet, mostly basally clumping.

Foliage/texture: Stems to 8 inches thick, medium glaucous to dark green, ribs 12 to 19 to 3/4 inch high, areoles white, glandular, mostly about 1/2 inch apart, spines 14 to 19, needle shaped, whitish rarely 2 inches long.

Flowers & fruits: Nocturnal, white to purplish to 3 inches long, fruit globose, red with red flesh to 3 inches in diameter.

Seasonal color: Flowers in spring and fruit in late spring to early summer.

Temperature: Tolerance similar to Organ Pipe cactus (Stenocereus thurberi). Tolerant to 28oF. In Phoenix, the urban heat island might just be enough to prevent cold damage, otherwise use in locations with good air drainage.

Light: Full sun

Soil: Requires well drained soils, especially if supplemental irrigation is being applied.

Watering: Little to none in Phoenix.

Pruning: None

Propagation: Seed

Disease and pests: Fungal and bacterial root rots if soil is poorly drained.

Additional comments: This is eventually a large columar cactus that is not for use in small spaces. Also, this wonderful columnar specimen is not recommended for use in highly pedestrian trafficed public areas such as the public paths along Tempe Town Lake because of vandalism wrought upon it by malicious and angry types. Propagates and transplants so easily.

Taxonomic quagmire: Yup, that's what I call it. This taxon is placed nearly equally across the Internet in four different genera. Here they are with their respective botanical authorities....

Pachycereus marginatus (A.P. de Candolle) Britton et Rose (1909)
Lemaireocereus marginatus (A.P. de Candolle) Berger (1929)
Marginatocereus marginatus (A.P. de Candolle) Backeberg (1942)
Stenocereus marginatus (DC.) A. Berger & F. Buxbaum, Published in: Botanische Studien 12:100 (1961)

I refer to this taxon as belonging to the genus Pachycereus, because this is the oldest published description. Overall, Pachycereus is a diverse genus with many species.