Silver torch cactus

Silver torch cactus: how do you recognise it?

Habit

Slender columnar cactus, upright to arching, about 1.5 m tall and 50 cm wide, often with side shoots at the base.

Stem

Thin, 5–8 cm across, with about 20–25 low ribs, completely covered in spines.

Spines

Dense, fine, silvery white and yellow-brown, short; they sit in groups on fixed spots (areoles).

Flower

Tubular, carmine to dark red, 6–9 cm long, only half opens; only on older plants.

Roots

Fine and shallow; it likes free-draining soil and rots with wet feet.

Plants: March–April

Why grow it?

• Striking silvery-white spines give the plant a special, soft look.
• Slender, architectural shape that takes up little space.
• Very easy: it tolerates drought and needs little water.
• Flowers on older plants with carmine-red tubular blooms, especially after a cool, dry winter rest.
• Can stand outside in summer and also tolerates lower temperatures if kept dry.

Silver torch cactus: where does it grow best?

• As sunny as possible: a south-facing window or conservatory is ideal; it tolerates full sun.
• Free-draining, sandy cactus compost; neutral to chalky.
• Dry: let the compost dry out completely between waterings.
• Warm in summer (18–30 °C); cooler and dry in winter, at 5–10 °C.
• A sturdy, rather heavy pot, because the column can become top-heavy.

Light

Sunny

Potting soil

Cactus compost

Acidity

Neutral or chalky

Watering

Sparingly

Size

1.5 m tall, 0.5 m wide

Temperature

Minimum 0 °C

Goes well with

• Echeveria: Low rosettes in soft colours at the foot of the column, with the same needs.
• Agave: A tough, leafy succulent that fits well in a sunny group.
• Gasteria: Tolerates slightly less light and gives dark, firm foliage as a contrast.
• Stonecrop: Low, drought-loving plants for a pot or container.
• Cereus: Another columnar cactus for a striking, sunny room corner.

Silver torch cactus: when and how to plant it?

Plant in March–April.

1. Repot in March–April, when the plant starts growing again.
2. Choose a pot with a drainage hole, preferably terracotta, only slightly larger than the rootball.
3. Use cactus compost or mix potting compost with a third of coarse sand, perlite or pumice.
4. Hold the plant with folded newspaper or thick gloves and set it at the same depth as before.
5. Wait about a week before watering so that damaged roots can heal.
6. Spread a thin layer of grit around the base to guard against rot.

Care

Water

In summer, water only when the compost is completely dry, then thoroughly. In winter hardly at all or not at all.

Feeding

From April to August, a cactus feed or one low in nitrogen every four weeks.

Light

As much sun as possible. It may stand outside in summer; acclimatise it gradually to the sun to prevent scorching.

Temperature

Summer 18–30 °C; winter cooler, 5–10 °C. Kept dry, it tolerates lower temperatures briefly, down to about 0 °C.

Repotting

Every two to three years in spring, or when the pot becomes too small or too light.

Tip: Give it as much sun as possible and stand it outside in summer. Keep it dry and cool in winter: it then tolerates lower temperatures and has a chance of flowering.

Silver torch cactus: when to prune it?

When: It is not pruned.

How:

• Remove soft, brown or rotten parts with a clean knife back to healthy tissue; let the cut surfaces dry.
• You can leave side shoots to form a clump or cut them off as cuttings.
• If the plant gets too tall, you can cut off the top and let it dry; the stem then often sends out side shoots.

Caution: Fine, sharp spines: wear thick gloves or use folded newspaper. Keep it out of reach of children and pets.

Pruning calendar and basic rules

Propagation

Cuttings

In spring or summer: cut off a side shoot or a piece from the top, let it dry for 1–2 weeks and stand it upright in dry cactus compost. Water only once roots have formed.

Seed

Sow in spring in sandy compost at 20–25 °C. Germination is slow; the seedlings grow slowly.

Silver torch cactus: how does it get through the winter?

• Not hardy in our gardens: keep it indoors, frost-free, in winter.
• In winter keep it bright and cool at 5–10 °C, and water hardly at all or not at all.
• Kept dry, it tolerates temperatures around 0 °C briefly, but cold and wet cause rot.
• In autumn bring it in before the nights get too cold.

Diseases and pests

• Stem rot: The stem turns soft, brown or black, especially at the base. Usually caused by too much water, especially in the cold. Cut away the affected part back to healthy tissue and let it dry; water less.
• Mealybugs: White cottony tufts hidden between the spines. Dab with a cotton bud dipped in alcohol or treat with a mild soap solution.
• Spider mite: Fine webbing and dull brown patches in dry, warm air. Rinse the plant and put it somewhere slightly cooler and better ventilated.
• Thin, pale growth: The top grows thinner and more pointed towards the light. Give it more light.
• No flowers: Too young, too little light or no cool winter rest. Give it a brighter spot and a cooler winter, and be patient.

Through the year

• January: Rest. Bright, cool (5–10 °C) and dry.
• February: Rest. Keep dry.
• March: Repot. Only then water very sparingly.
• April: Repot. Gradually water more as growth starts. Begin feeding.
• May: Slowly acclimatise to the sun or put outside after the last frosts.
• June: Water when the compost is dry. Feed every four weeks.
• July: Growing season. Possible flowers on older plants.
• August: Last feed. Take cuttings.
• September: Less water. Stop feeding.
• October: Bring indoors before it gets cold. Almost stop watering.
• November: Rest. Dry and bright at 5–10 °C.
• December: Rest. Keep dry.

Did you know?

• The name Cleistocactus comes from the Greek ‘kleistos’, closed, because the tubular flowers only half open.
• In the wild the red tubular flowers are visited by hummingbirds, which drink the nectar.
• The dense, white spines help the plant in the mountains to protect itself against strong sun and cold nights.