Old man cactus

Old man cactus: how do you recognise it?

Habit

Upright, unbranched column, 20–50 cm tall in a pot and rarely more than 10 cm thick.

Hairs

Long, soft, silvery-white hairs that wrap the whole plant and protect it from strong sun.

Spines

Sharp, yellow to grey spines under the hairs: take care when handling it.

Ribs

Many narrow ribs, hidden under the hairs.

Flower

Only on old plants several metres tall, from a woolly head on one side of the stem; never indoors.

Plants: March–April

Why grow it?

• A striking, white-haired column that stands out on any sunny windowsill.
• Grows so slowly that it fits the same spot and pot for years.
• Very frugal with water: ideal if you are short of time.
• Tolerates full sun and dry indoor air.
• A fine vertical accent in a bowl of low cacti and succulents.

Old man cactus: where does it grow best?

• The sunniest spot in the house: a south or west window. The white hairs protect it from the sun.
• Very open, mineral cactus compost with coarse sand, grit or lava granules; a little lime is fine.
• Warm and sunny in summer; it can go outside under cover, sheltered from rain.
• Dry and cool in winter at 10–15 °C, never below 10 °C.

Light

Sunny

Potting soil

Cactus compost

Acidity

Neutral or chalky

Watering

Sparingly

Size

0.5 m tall, 0.2 m wide

Temperature

Minimum 10 °C

Goes well with

• Bishop’s cap: Just as frugal with water and lovely beside the white column.
• Golden barrel cactus: A golden, globe-shaped cactus as a contrast to the white column.
• Mammillaria: Low cushion cacti that do flower freely.
• Aloe: A rosette-forming succulent that tolerates the same sunny spot.

Old man cactus: when and how to plant it?

Plant in March–April.

1. Repot in March or April, only when the plant outgrows its pot, every three or four years.
2. Choose a sturdy pot with a drainage hole; terracotta dries out faster and is less likely to tip over.
3. Mix cactus compost with a third to a half of coarse sand, grit or lava granules.
4. Hold the plant with a rolled-up newspaper or thick gloves and set it at the same depth as before.
5. Repot into dry compost and wait a week before the first watering.

Care

Water

From April to September water only when the compost is completely dry, onto the compost and not over the hairs. Empty the saucer.

Feeding

During the growing season, cactus feed at half strength once a month.

Hairs

Blow dust away or remove it with a soft brush. Wet hairs mat and turn grey.

Winter rest

From November to February dry and cool, as bright as possible.

Acclimatising

After winter, get it used to full sun gradually.

Tip: Always water onto the compost and never over the hairs: wet hairs mat and turn grey. Full sun and a dry, cool winter keep it beautifully white.

Old man cactus: when to prune it?

When: The old man cactus is not pruned.

How:

• Remove dead leaves and debris from between the hairs with tweezers or a soft brush.
• Cut a rotten patch at the base well back into healthy tissue; let the wound dry thoroughly.
• If the base has rotted completely, cut off the healthy top, let it dry for a few weeks and root it again in dry cactus compost.

Caution: Sharp spines hide under the soft hairs: wear thick gloves.

Pruning calendar and basic rules

Propagation

Seed

The usual method. Sow in spring on moist, fine cactus compost without covering, under glass at 20–25 °C. The seedlings grow very slowly.

Top cutting

Rarely needed, as it hardly branches. Let a cut-off top dry for a few weeks, then stand it on dry cactus compost.

Old man cactus: how does it get through the winter?

• House plant: never below 10 °C.
• From November to February keep it completely dry, cool (10–15 °C) and bright.
• A warm, wet winter makes it soft and prone to rot.
• In March, carefully start watering a little again.

Diseases and pests

• Rot: A soft, brown or black base caused by overwatering or a cold, wet winter. Cut well back and water far more sparingly from then on.
• Mealybug: White fluffy tufts that are hard to spot among the hairs, or on the roots. Remove with a brush dipped in methylated spirit; for root mealybug, repot and rinse the roots clean.
• Greying hairs: Hairs turn grey or dirty from dust, watering or age. Water onto the compost and remove dust with a brush.
• Thin, pale top: Caused by too little light, especially in a warm winter. Give it a sunnier spot and a cool winter rest.

Through the year

• January: Leave it dry, cool and bright.
• February: Still no water.
• March: Carefully start watering a little. Repot if needed.
• April: Get it used to full sun gradually.
• May: Cactus feed once a month. Possibly outside under cover.
• June: Water when the compost is completely dry, onto the compost.
• July: Water and feed. Blow dust out of the hairs.
• August: Last feed.
• September: Water less. Bring it in before cold nights.
• October: Very little water.
• November: Winter rest: dry and cool at 10–15 °C.
• December: Leave it dry and bright.

Did you know?

• Senilis is Latin for ‘of an old man’, after the white hairs.
• The genus name Cephalocereus refers to the woolly ‘head’ (cephalium) that mature plants form on one side of the stem; the flowers emerge from it.
• Like almost all cacti it is covered by the international CITES trade rules: always buy cultivated plants, never plants taken from the wild.