Old Man Cactus (Cephalocereus senilis)

Bunny Cactus, Old Man Cactus, White Persian Cat Cactus

Old man cactus (Cephalocereus senilis) is a cactus native to eastern Mexico. Old man cactus is widely cultivated in gardens and as a houseplant, resulting in dwindling numbers of old man cactus that grow in the wild. This species is popular due to its woolly appearance. Old man cactus grows best in well-drained soil and bright sunlight, which cause the hairlike fibers to grow.

I. Appearance and Characteristics 

Cephalocereus senilis, the old man cactus, is a species of cactus native to Hidalgo and Veracruz in central Mexico. It is threatened in the wild, but widespread propagation and popularity in cultivation have reduced the demand on wild populations.

Cephalocereus senilis is a tall, columnar species with clusters of stems that may grow to 5–15 m tall; the individual stems are usually unbranched, being unable to withstand the weight of side branches adequately. The most striking feature is the shaggy coat of long, white hairs suggestive of unkempt hair on an old man. The coat is a particularly striking silvery white on the young cactus; as the plant ages the stem begins to lose its covering. The flowers are red, yellow, or white, though the plant may not flower until 10–20 years old.

Cephalocereus senilis is a very popular cactus in cultivation, grown for its woolly appearance. It prefers a very well-drained soil mix (more so than many other cacti), and much bright sunlight, which encourages growth of the hair.

II. How to Grow and Care

Sunlight

Old man cactus is a heliophilic plant and needs sufficient sunlight for its growth and blooming. It can be placed on the outdoor balcony or in the garden without shade. However, long-time exposure to blazing sunlight should be avoided in hot summer, when it needs to be shaded or cooled a little to prevent high temperatures from damaging it.

Temperature

Old man cactus is distributed throughout tropical, subtropical, and semi-desert regions with scarce rainfall, intense sunlight, and hot temperatures. The optimum temperature for growth is 20 to 35 ℃. Lower than 10 ℃ or higher than 35 ℃, growth slows and dormancy begins. The air humidity should not be too high and the environment should be well-ventilated. Avoid high humidity and accumulated water.

Watering

Old man cactus is a drought-tolerant plant that does not require frequent watering. Water thoroughly when the soil is completely dry. When potted, water slowly, wait for water to flow out the bottom, and then pour the excess water from the tray to avoid water accumulation.

Spring, summer, and fall are its growing seasons. Water once or twice a week to keep the soil slightly wet. In winter, water less; just keep the soil from drying excessively; usually once a week. Besides, water with rainwater or distilled water rather than tap water.

Tap water contains a lot of calcium, magnesium, and other mineral salts. Long-term use tends to cause soil compaction. Avoid splashing water on its stem when watering to prevent rotting.

Soil

Old man cactus grows best in fertile, gravel-rich, water-permeable soil with a pH value of 6-7. The culture soil formula often used is 60% vermiculite + 20% coco coir or peat moss + 20% sandy soil. A small amount of organic potting soil can also be added. Lightweight culture media such as vermiculite can be added to improve the air permeability of the soil. Eggshell powder or vermicompost can also be added to increase the soil fertility.

Roots of old man cactus are very sensitive to oxygen deficiency. If the soil is poorly permeable to air and water, root rot can set in. It’s easy to judge permeability: when watering, water should pass through the medium quickly, rather than stop at the soil surface and slowly seep down. Repot and loosen the soil every year to ensure the air permeability of the soil.

Fertilizing

In growing seasons (namely spring, summer and fall), fertilize old man cactus once a month with liquid fertilizer. No fertilizer is required in winter. A small amount of slow-release fertilizer can be well mixed into the soil when repotting in spring or fall.

Use nitrogen fertilizer during seedling and phosphate-potassium fertilizer before and after blooming. The fertilizer concentration should be as low as possible. It would be better to apply low-concentrate fertilizer several times rather than to use a high concentration. If the base is yellow and grows slowly, the cause may be excessive fertilizer, and fertilization should be immediately stopped.

Planting Instructions

Sow, plant, or repot in spring or fall when the temperature is 15 to 20 °C . Keep air humidity high when seeding. Use plastic film to cover the soil and remove it after the seeds germinate.

Use permeable clay flower pots for potted plants. Too large a flowerpot accumulates water easily, while too small a flowerpot limits the development of roots. Before planting, expose soil to blazing sunlight and disinfect to kill pathogens.

If planted in the garden, an old man cactus prefers an area with full sun and loose soil. Remove all weeds and replace the soil if needed to ensure good water permeability and avoid root rot. Wear gloves or use tongs when planting to prevent your fingers from getting pricked. You can also wrap the plant in a towel to help you move it.

Pruning

Old man cactus does not require much pruning. Remove withered flowers and branches so the plant uses nutrients on healthy growth.

Propagation

Propagating the Old Man Cactus can be done through various methods, including seeds, offsets, and stem cuttings. Each method has its own advantages and considerations, so let’s take a closer look at each one.

  • Seeds

Starting from seeds is the most time-consuming method of propagation. It can take anywhere from two to five years for the cactus to become established. To begin, collect the seeds from mature fruits and sow them in a well-draining cactus mix. Keep the soil lightly moist until the seeds germinate, then gradually reduce watering. Patience is key with this method, as it may take several years before you see substantial growth.

  • Offsets

The Old Man Cactus naturally produces offsets or “pups” that grow at the base of the main plant. These offsets can be carefully removed and planted in their own pots. Before separating an offset, make sure it has developed its own roots and is at least one-third the size of the parent plant. Allow the offset to callus for a few days before planting it in a well-draining medium. Water sparingly until the new plant establishes strong roots.

  • Stem Cuttings

Stem cuttings are a quicker way to propagate the Old Man Cactus. Select a healthy stem and use a sharp, sterilized knife to cut a piece that is about 6 inches long. Allow the cutting to callus for a few days before planting it in a well-draining medium. Place the cutting in a warm location with moderate light and maintain a minimum temperature of 70 degrees Fahrenheit for optimal rooting. Water sparingly until the cutting develops a strong root system.

Repotting 

You should repot your Cephalocereus senilis (Old Man Cactus) once every 2 year(s). This helps your Cephalocereus senilis (Old Man Cactus) to stay healthy for many years.

Pests and Diseases

Common Pests

The Old Man Cactus is known for its resilience and resistance to pests and diseases. However, it is still important to monitor the plant closely for any signs of common cactus pests.

One such pest is the mealybug, which can hide in the cactus’s shaggy hair. Regular inspections and prompt action can help prevent a mealybug infestation.

Scale insects are another potential threat, and they too can find shelter in the cactus’s hair. If scale is detected, it is crucial to address the issue promptly to protect the health of the plant.

Common Diseases

The Old Man Cactus is generally resistant to diseases, but overwatering and poor drainage can lead to root rot. It is important to ensure that the soil is well-draining and not kept consistently moist. If root rot is detected, it is essential to take immediate action to save the plant. This includes removing the affected roots, allowing the plant to dry out, and adjusting watering practices to prevent further damage.

Prevention Tips

  • Inspect the cactus regularly for pests, paying close attention to the stems and shaggy hair.
  • Address any pest infestations promptly using appropriate treatments, such as insecticidal soap or neem oil.
  • Maintain proper watering practices, allowing the soil to dry out between waterings to prevent root rot.
  • Keep the area around the cactus clean, removing fallen leaves and debris to discourage flying pests.
  • Avoid over-fertilizing, as this can lead to excessive foliage growth and weaken the plant.

III. Uses and Benefits 

Old man cactus is an excellent choice for growing in cactus gardens, rock gardens, and xeriscapes. However, this tall cactus also thrives when grown outdoors in pots on terraces and balconies. The plant’s surface becomes covered in an intriguing dense web of hair-like growth that also makes this cold-tolerant plant an exciting specimen plant in gardens with plenty of sunlight.

IV. Harvesting and Storage

Most fruits of old man cactus are edible. Pick the fruit when they turn red. Avoid food safety issues by confirming the species with experts. Wear gloves or use scissors and other tools to harvest.

Old Man Cactus (Cephalocereus senilis) Details

Common name Bunny Cactus, Old Man Cactus, White Persian Cat Cactus
Botanical name Cephalocereus senilis
Plant type Houseplant
Hardiness zone 9a, 9b, 10a, 10b, 11a, 11b
Growth rate Slow
Height 16 ft. 0 in. - 50 ft. 0 in.
Width 16 ft. 0 in. - 50 ft. 0 in.
Sunlight Full sun (6 or more hours of direct sunlight a day)
Soil condition High Organic Matter
Flower color Gold/Yellow