Old Man Cactus
Cephalocereus senilis
The Old Man Cactus is a striking columnar species renowned for its thick, shaggy coat of long white hairs. These 'hairs' are actually modified radial spines that act as a natural sunscreen, protecting the cactus from the intense UV radiation of its native Mexican habitat. While it appears soft and fluffy, sharp yellow central spines are hidden beneath the woolly exterior, making it a plant that is better to look at than to touch. It is a slow-growing, long-lived specimen that adds a unique architectural element to any desert-themed collection.
Light
Full Sun
Water
Low
Difficulty
Moderate
Humidity
Low
Pet Warning
While not chemically toxic, the sharp spines hidden beneath the white hair are very dangerous and can easily puncture the skin of humans or pets. Handle with extreme caution using thick gloves or towels.
Care Guide
Lighting
This cactus requires intense, direct sunlight to maintain its signature white hair. Place it in a south-facing window or the brightest spot in your home. Insufficient light will cause the plant to stretch (etiolate) and the hair to become sparse.
Watering
Use the 'soak and dry' method. Water the soil thoroughly until it drains from the bottom, then wait until the entire root ball is completely dry before watering again. During the winter dormancy, reduce watering to almost zero—once every 2 months is usually sufficient.
Temperature and Airflow
Provide warm temperatures between 65°F and 85°F (18°C-29°C). Good air circulation is vital to prevent moisture from becoming trapped in the hair, which can lead to fungal infections. It is not frost-tolerant and should be kept away from cold drafts.
Potting and Soil
Always use a pot with drainage holes, preferably made of unglazed terracotta to help moisture evaporate. A gritty, well-draining cactus mix is essential. You can enhance drainage by adding pumice, perlite, or coarse sand to a standard cactus soil.
Cleaning the Hair
Over time, the white hair can accumulate dust. You can carefully clean it using a soft, dry paintbrush or by blowing air gently over the plant. Avoid getting the hair wet during watering, as this can lead to rot or discoloration.
In-Depth Care & Growth
Feeding & Soil
Fertilizer
Low-nitrogen cactus fertilizer
Soil
Extremely well-draining, gritty cactus mix with a high inorganic content.
Physical Attributes
Mature Size
1-2 feet indoors, up to 40 feet in the wild
Growth Rate
Slow
Propagation
Most commonly grown from seed; can be propagated from stem cuttings, though they take a significant amount of time to root.