Botanical Name — Cephalocereus senilis
Common Name — Old Man Cactus
Plant Family — Cactaceae
Cephalocereus senilis are columnar cacti known for growing up to fifty feet tall in the wild. White fuzz blankets their stems, giving the plant the fitting common name of Old Man Cactus. This sagely specimen will not produce flowers until it is at least 15 years old, so cactus flower fans will have to be patient. It is native to the states of Hidalgo and Veracruz in Mexico.
- Cephalocereus senilis requires plenty of full sun. Eight hours of direct sunlight a day is ideal but at a minimum these plants should be provided with at least five hours.
- If you are growing them indoors, a spot in a south facing window is ideal.
- These cacti thrive in low humidity and temperatures above 70 ºF.
- Being from a mountainous climate, they can withstand regular drops below freezing temperatures as long as they are dry. Their natural environment gets next to no rain in winter. If winters are rainy or snowy, it is advisable to bring them indoors once night time temperatures consistently fall below 50 ºF.
- Cephalocereus senilis are extremely drought tolerant. Water them thoroughly, fully saturating the soil. Always allow the soil to dry out completely in between waterings.
- If you are unsure whether or not the soil is dry, wait a few days before watering. It is much better to underwater than overwater. Excessive moisture can quickly lead to root rot.
- During the winter, water only once every two months or so.
- These plants prefer a gritty, sharply draining mix. Use cactus soil or amend regular potting mix with sand and fine pumice up to 50% to improve texture and drainage.
- In desert climates these plants can be potted directly in the earth and grown outdoors year round.
- Cephalocereus senilis flower in late spring and early summer. They are nocturnal bloomers, revealing bright yellow and rosey red.
- Cephalocereus senilis do not require fertilization, however a boost of nutrients during the growing season will help them thrive. Use a fertilizer formulated specifically for cacti and succulents, once a month, during spring and summer only.
- These plants rarely branch, but offshoots can be propagated by separating the roots of the mother plant from the pup. Repot right away and you have a new baby cactus!
- Cephalocereus senilis can also be grown from seed. Sow seeds just below the surface, using a well-drained soil mix. Provide a humid microclimate to encourage germination and keep soil evenly moist during the first few months to encourage seedling growth.
- These cacti are not especially prone to pests and diseases. Root rot can easily occur if the plant is overwatered. Keep an eye out for common pests such as mealybugs, aphids and scale.
Maintenance (pruning, legginess, repotting)
- These hardy plants require very little maintenance. Container grown cacti prefer to be rootbound, so repotting should be necessary only once every two years. Repot into a planter 2” larger in diameter to give the plant plenty of room to continue growing.
- Cephalocereus senilis is not toxic to humans or animals, but shouldn’t be ingested. Spines are sharp beneath the fuzzy exterior, so it is advisable to keep out of reach of pets and small children.