The Old Man Cactus (Cephalocereus senilis) earns its name from the tufts of snowy, white ‘hair’ that covers the surface of the cactus. These showy cacti are grown primarily as houseplants as they need hot, dry growing conditions similar to their native habitat in Mexico. They can survive outside in USDA plant hardiness zones 9 and 10 and can reach heights of 45 feet (in 10 to 20 years) when grown in the wild. When grown in containers as houseplants, they remain small, rarely reaching heights of more than 3 feet.
Light and Temperature Requirements
The old man cactus needs lots of sunlight and heat during the summer. Place it in a location that receives at least 6 to 8 hours of full sun, but aim for a much a sun as you can give it. All day sun is ideal. If you are growing your cactus inside put it in a southern or western window during the summer.
During the winter, the old man cactus prefers bright light in a much cooler setting. It thrives in winter temperatures between 50 and 60 degrees. Avoid placing your old man cactus near heater vents where it will be subjected to hot drafts, but also avoid locations near drafty windows where cold drafts can damage your plant.
The old man cactus thrives in a hot, dry environment, but that doesn’t mean you can ignore its watering needs. It prefers soil that dries out completely, but then enjoys an occasional good soaking, too. Avoid the temptation to give your old man cactus a little water now and then as this can cause the roots to rot. Planting your old man cactus is a terracotta or other unglazed plant pot will also help prevent rootrot as it will absorb the moisture from the soil keeping the soil drier.
Water your old man cactus thoroughly to saturate the soil and then allow the soil to dry out completely before watering it again.
Soil & Fertilizing
Old man cactus requires loose soil that drains quickly and should not be grown in all-purpose potting soil. Purchase a quality cactus and succulent soil mix or make your own by mixing three parts all-purpose potting soil, two parts builder’s sand and one part perlite.
Fertilize your old man cactus with fertilizer designed for cactus in the spring. Follow the application rate on the container. Avoid giving your old man cactus more fertilizer than is recommended as it can stress the plant and damage the roots.
Deadheading and Pruning
The old man cactus does not require pruning and rarely requires deadheading. While old man cactus produces showy pink, white or red blooms in the wild, it rarely blooms in cultivation. However, should your old man cactus bless you with a midnight bloom or two, removing the spent blooms as soon as they fade will improve the appearance of the plant.
Growing Old Man Cactus from Seed
Growing old man cacti from seeds can be a fun project, but it isn’t very practical as they germinate slowly (up to 3 months) are slow growing and can take a long time to reach a stage that looks like a cactus. For this reason, it is recommended that you purchase an established cactus plant from your local nursery or home improvement center.
Grooming Your Old Man Cactus
Due to its hairy nature, your old man cactus may collect dust and other airborne particles in its hair causing it to discolor or look dull. Fortunately, this is easy to fix with a gentle shampoo. Here’s how:
- Rinse the cactus under tepid running water to wet the hairy spines. Avoid hot or cold water as this will stress your cactus.
- Lather with a mixture of Castile soap and water working it gently over all the hairs with your hands.
- Rinse the soap away under running water, using care to remove all the soap residue.
- “Comb” the hairs with your hands so that they are help upward and away from the body of the cactus.
- Place the cactus in a warm, well ventilated area where it will dry quickly. If necessary, use a fan to circulate air in the room and speed drying.
The old man cactus is a delightful addition to a cacti and succulent collection, but it can be dazzling as a stand-alone cactus too. These attractive houseplants add atmosphere and variety to the home or office and are a great way to fill a sunny window that is too hot for other houseplants in the summer.
Always purchase old man cactus from a reputable source as over-harvesting them in the wild has led to them becoming an endangered species in some