How to Care for an Old Man Cactus

The old man cactus is a fun addition to an indoor garden. It is cleverly named "old man" due to the whitish fuzzy coating that looks like unruly white hair. Additionally, it is referred to as such because in the wild, it can live for up to 200 years. It is also sometimes referred to as the "hairy cactus" or "bearded cactus." The botanical name for this cactus is ​Cephalocereus senilis​ (USDA zones 9-11)​.​

These white hairs are not just an aesthetic; they serve several purposes. The hairs help the cactus retain water and form a protective shield from both cold and hot weather. While the white hairs may look soft to the touch, beneath them are sharp yellow spines, so use caution when touching them. This unique and fun cactus makes an excellent indoor plant. It can add some variety to your indoor garden, and it will bring a lot of personality to your home.

Place the cactus in front of a southern- or western-exposure window to get direct sunlight. This plant likes full sun and hot weather. Try to mimic its native desert conditions as much as possible. If you are concerned that your cactus is not receiving enough sunlight from the window alone, you can use a grow light.

You can encourage the old man cactus to be winter dormant by adjusting its growing conditions. The old man cactus prefers a winter temperature of 50 to 60 degrees Fahrenheit. It can have less water in the winter as well. It still requires the same amount of light in the winter.

You can give the old man cactus some fertilizer. Dr. Earth makes a 5-5-5 fertilizer that is great for cacti. Add the fertilizer to the water. It only needs to be applied one or two times in the summer. If using an all-purpose plant fertilizer, dilute it to quarter strength. A water-soluble, low-nitrogen fertilizer is a good alternative.

As with all cacti, be sure not to overwater. Allow the soil to completely dry out before watering. When watering, drench the soil completely, and allow the soil to dry again before rewatering. Overwatering can result in root rot, which can be very damaging to the cactus. The old man cactus can be watered less in the winter.

Use specialty potting mix made specifically for cacti. Another option is using general potting soil and sand, creating a half-and-half mixture. Choose a general potting soil that has a high mineral content to provide sustenance. You can also create a succulent mix by using 3 cups of specialty cactus potting soil, 3 cups of sand and 1.5 cups of perlite or pumice. This provides great soil aeration and also allows excess water to drain.

Always pot your cactus in a pot with one or more drainage holes at the bottom to allow water to escape in case of accidental overwatering. Terracotta or unglazed pots are best since they soak up excess water. You do not need to repot your old man cactus frequently. It only needs to be repotted every three to five years.

The white fuzzy hairs can get dirty or turn brownish over time. You can give them a cleaning by mixing a small amount of liquid castile soap and water. Organic is best, and you should use an unscented castile soap free of dyes. Other organic soaps will also suffice. Carefully wash off all the soap in the sink or with a hose. Make sure the soap does not seep into the soil. Comb the hair — yes, actually comb the hair — upward to help it dry.