Pachycereus marginatus
Family: Cactaceae​
​Common Name: Mexican fence post
Origin: Pachycereus marginatus likely originated from central Mexico, within the states of San Luis Potosí, Querétaro, Guanajuato, Hidalgo, and Oaxaca. However, due to its prevalence, the exact origin is known.
Description: The Mexican fence post is a dark-green columnar cactus that develops basal branches when mature, possessing 5-7 ribs. Stems are rough and erect, growing up to 4 m in cultivation, and 15 m in the wild. Cacti are spined along each rib, with mature cacti possessing shorter spines than juvenile specimens. During the spring, pink to green flowers will develop from areoles, leading to spiny red fruits.
  • Interesting Features:
    • The areoles of P. marginatus create a confluent line among each rib, to an interesting visual effect, especially when blooming. As the spines and flowers only emerge along each rib, the cacti is leant a “neat” appearance that is popular in cultivation.
    • This species grows exceptionally quickly – up to 1 m yearly when planted outside.
  • Uses: The Mexican fence post is commonly used to create living fences, and it is often used as the focal point within desert landscapes and gardens, from its striking appearance.
    • Additionally, the developing fruits may have been consumed within its natural habitat, as with many other Pachycereus species, and cacti extracts have been found to possess anti-tumor properties.

Cultivation and Care:
  • Watering: Moderate
    • Provide moderate irrigation during the summer months, until well established.
    • During the winter, suspend watering, providing only sparse irrigation when necessary.
  • Soil: P. marginatus should be planted in a rich and well-draining cactus or succulent soil, with a pH between 6.1 and 7.8.
  • Lighting: Site in a location that receives full sunlight. For indoor species, provide as much direct light as possible - a grow light may be necessary for this species to thrive.
  • Propagation: The Mexican fence post can be propagated from seed as well as softwood and woody stem cuttings. There are no difficulties in propagation – seed germinates easily, as do cuttings, if allowed to completely callous over before planting.
  • Cold Tolerance: 25°F, USDA hardiness zones 9b – 11.
  • Special Accommodations: Pachycereus marginatus should be given a winter dormancy period in order to encourage growth, and should be repotted frequently, as specimens can easily outgrow containers.

Sources:
  1. Llifle Encyclopedia of Cacti
  2. World of Succulents
  3. Horticulture Unlimited
  4. Dave’s Garden
  5. Matt’s Landscape
  6. University of Washington
  7. JSTOR
  8. Academic Journals