Old Man Cactus
Cephalocereus senilis
Old Man Cactus is a columnar cactus covered in long white hairs that act like a natural sunscreen in its native Mexico. Soft-looking from a distance, it hides sharp yellow spines underneath, so handle with thick gloves. It grows slowly and can live for many years in a bright, dry spot.
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 Notes
Light
Give intense, direct sun so the white hair stays dense. A south window or the brightest spot in the home works best. Low light stretches the plant and thins the hair.
Water
Soak thoroughly, then wait until the whole root ball is dry before watering again. In winter dormancy, water very rarely, often only every couple of months. Avoid wetting the hair, which can lead to rot or discoloration.
Soil
Use a gritty cactus mix with pumice, perlite, or coarse sand in an unglazed terracotta pot with drainage holes. Fast drainage is essential.
Humidity and Temperature
Prefer 65°F to 85°F (18°C to 29°C) with good airflow so moisture does not linger in the hair. It is not frost-tolerant. Dust the hair carefully with a soft dry brush rather than washing it.
Common Issues
Soft tissue or black spots usually mean too much water or poor airflow. Sparse hair and stretching mean more light is needed.
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.
Common Varieties
No widely recognized cultivars; variations exist primarily in the density and length of the white hair.
A tall columnar cactus with a dense covering of long white hair-like spines that vary in length and thickness from plant to plant.