Cephalocereus senilis (Old Man Cactus)

Easily recognized for it’s grayish white “hairs”, the Old Man Cactus is a native to Mexico. It is highly prized as an ornamental succulent for its unique adaptation which reduces transpiration. Unfortunately, this has led to illegal overharvesting and severe reduction in mature populations.

Cephalocereus senilis (Old Man Cactus)
Deciduous: no
Hardiness Zones: 9-10, tolerant to 5 degrees Celsius (40 Fahrenheit)
Height: to 12 meters (40 feet) tall
Diameter: stem to 25 centimeters (10 inches) in diameter
Growth Rate: slow
Age: reaches maturity around 200 years old
Root System: deep taproot with extensive lateral roots
Family: Cactaceae
Subspecies: none
Tolerates: drought, intense heat, xeric (dry and hot) conditions
Problems (major): root rot, endangered (according to IUCN), mealybugs, spider mites, phytophthora (fungal infection)
Problems (minor): none
Poisonous: no
Soil requirements: requires light/sandy, well-drained soils, appreciates light slow-release fertilizers
Air requirements: native to regions with very low humidity
Watering requirement: Low, allow the top centimeter of soil to completely dry out in between watering.
Sun requirement: Constant full sun, more sunlight increases “hair” length.
Primary photosynthetic organ: green stem covered in thick gray-white “wool”
Leaf structure: small yellow spines in clusters of 1 to 5
Flowering structure: to 5 centimeters (2 inches) wide, pale pink
Flowering frequency: midsummer, typically June-July
Fruit: to 3 centimeters (1 inch) wide, deep pink, dispersed by house finches
Reproduction by offsets: yes
Monocot or dicot: dicot
Form: columnar, minimal shoot girth increase with age

Notable characteristics:
The wool-like substance covering the entire shoot section of these plants and hides the sharp leaves. The “hairs” can actually be cleaned using regular shampoos and conditioners.

Old Man Cacti are typically grown as ornamentals or biological specimens.

Sources used:

New “hairs” emerging from apical section of a stem

Stem without much “hair” and visible spines
All of the images provided were taken by me. They may be used for educational/informational purposes only, provided that this article/online journal is appropriately cited first.

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