Silver Torch Cactus: Care and Propagation Guide

The Silver Torch cactus (Cleistocactus strausii) also called Wooly Torch or the Snow Pole cactus is a columnar succulent native to mountainous regions of Bolivia, Peru, Uruguay, and Argentina. It is abundant in its native habitat since it has no threats to its survival.

Silver torch cacti have spectacular features that make them attractive plants for landscape and container gardens. They are quite large but you can grow them as houseplants outside their hardiness zones. Care and maintenance are easy and you won’t have any difficulty growing this cactus.

Description and features

Cleistocactus strausii is a tall columnar plant that can reach a height of 10 ft. (3 m) and about 2.5 inches wide. The main plant may also branch at the base to form more stems. This means you need enough space in your home if you want to add it to your cactus collection.

The stems are lined with ribs which are densely covered in white spines. This gives the plant a silvery-grey appearance. Only mature silver torch cactus produce around summer. The long tubular deep red or burgundy flowers protrude horizontally and radially from the stems and they hardly open.

In summary, here is what to know about the silver torch cactus:

Common names	Not toxic to pets or humans.
Botanical names	Cleistocactus strausii
Cactus size	3 to 10 ft. height and spreads 3 to 6 ft.
Sunlight	Full sun but not intensively hot.
Temperature	68 to 77°F during spring and summer and around 50-59°F (10-15°C) during winter.
Soil type	Sharp draining succulent mix.
Blooming	Late summer
Flower color	Deep red or burgundy.
Hardiness Zones	USDA 9a to 11b.
Toxicity	Not toxic to pets or human.

Silver torch cactus care

Growing and caring for the silver torch cactus is not a hard task as long as you understand what it needs in terms of light, soil type, temperature, and watering. In warm climates, these plants can be grown outdoors year-round. 

However, It is recommended to bring them indoors when nighttime temperatures consistently drop below 50 ºF.

Light requirements

Silver torch cactus needs full sunlight for 4 to 6 hours a day. However, it prefers some shelter when the sun gets intensively hot. Too much direct sunlight can cause sunburn on the cactus. On the other hand, if it doesn’t get enough sunlight, it will grow spindly and won’t bloom.

Watering

As a desert cactus, the silver torch can go several days without water. During the growing season (spring and summer) water them thoroughly, fully saturating the soil. But, let the soil dry completely between the waterings. Waterlogged soils can quickly lead to root rot.

During winter, cut back on watering to allow the cactus to rest for better growth and blooming ahead. Just mist the soil when it’s completely dry to prevent the cactus from shriveling. Make sure you don’t spill the water on the stems.

Temperature

Cleistocactus strausii is happy at room temperature (68 to 77°F). However, it prefers even cooler temperatures during winter. Keep the temperature to around 50-59°F (10-15°C) during its resting period. 

Humidity

Silver torch cactus prefers low humidity conditions. Aim for an indoor humidity level between 30 and 40 percent. High humidity can lead to fungal problems and rot. 

Fertilization

This cactus can benefit from moderate fertilization during the growing period. Feed once monthly with a well-balanced cactus fertilizer diluted to half strength to stimulate growth. Silver torch cactus don’t need fertilizer during winter.

Potting and repotting

Silver torch cacti can be grown directly in the ground in warm climates or in containers outside their hardiness zone. The soil must be well draining and rich in nutrients. Plants grown in pots may need to be repotted every two to three years or when the roots get too compacted.

When repotting, use a slightly larger pot than the current one. It must have drainage holes at the bottom. You may use a cactus mix or make your own cactus soil by mixing standard potting soil, coarse sand, and pumice.

How to propagate silver torch cactus

The silver torch cactus can be propagated by rooting the cuttings of small branches that form at the base of a mature plant. However, this leaves an ugly scar on the cactus which can also expose it to rot and fungal infections. 

If you remove the cutting for propagation, allow the scar on the parent plant to dry out for a week before watering. Propagation should be done during spring or summer.

To propagate by cuttings:

1. Take a cutting from a branching stem of the main plant using a clean sharp knife.
2. Let the cutting callus over for a week or two before planting it in a well-draining cactus mix. You may apply a rooting hormone to stimulate a quicker root formation.
3. Mist the soil and place the pot in a warm place with bright, indirect light. Be sure to water the cutting whenever the top inch of the soil feels dry.
4. The cutting will root in four to eight weeks and you can transplant it to your preferred location.

If you are concerned about the dangers of taking a cutting from your cactus, propagation by seed is a safer and quicker option. Simply get seeds from a reputable source and plant them in a cactus mix. Water the soil and keep the pot in a warm location with bright indirect light.

The seed will germinate in less than 6 weeks and you can transplant the cactus seedlings to your preferred location.

Pests and diseases

The silver torch cacti are prone to common succulent pests such as mealybugs, scale, and spider mites. They can be identified by the white masses and black spots on the cactus. These pests can weaken or kill the cactus because they suck juices and nutrients from the plant. 

To get rid of pests on your cactus you can treat it with neem oil or insecticidal soap. You can also hose off visible pests with a strong strand of water or remove them using cotton swabs dipped in isopropyl alcohol. Root mealybugs can be difficult to detect and control since they reside underground. 

This plant is also susceptible to root rot when overwatered. This is a serious condition that silently kills many plants. Bacteria and fungi that cause root rot thrive in damp soil conditions. So, it’s important to keep the soil on the drier side than overwatering. 

Final Thought

Silver torch is an eye-catching plant you would want to add to your landscape or indoor cacti collection. It’s relatively easy to grow and maintain. Simply grow it in well-draining soil, ensure it gets full morning sun, and water it only when the soil is completely dry.

Like most cacti, it thrives in warm temperatures but needs cool conditions during winter. The plant may benefit from a cactus fertilizer during growth seasons. It’s also important to repot it every two to three years or when it gets excessively pot-bound.

References and citations

Florilegium – Cleistocactus strausii, The university of Arizona

Anderson, Edward F. The Cactus Family. 1st ed., Timber Press Incorporated, 2001.

“Insect Pests of Cacti and Succulents Grown as House Plants,” Missouri Botanical Garden.