Pilosocereus azureus (Blue Torch Cactus)

Pilosocereus azureus

Last updated on September 11th, 2022 at 12:36 pm

Pilosocereus azureus, also known as the blue torch cactus, can make an excellent addition to any garden where it’s the only cactus you have or one of many different types of plants.

The blue torch cactus makes a great accent plant in your garden, and its unique appearance will certainly attract attention from visitors and passersby alike.

Pilosocereus azureus was named after its gorgeous blue, violet, or lavender spines, which shimmer in the sun, looking like blue flames.

This exotic, tropical-looking cactus has been used as an ornamental plant in gardens and pots across the world since the beginning of the 20th century because of its beautiful color and it is still popular among collectors today.

Here are some tips on how to care for Pilosocereus azureus and keep it growing its best year after year.

Origin and distribution

Pilosocereus azureus is a cactus native to Mexico. It is found in the states of Tamaulipas, Veracruz, and Puebla. The plant grows in rocky, mountainous regions at elevations of 1000-2000 meters. Azureus are planted by specialist collectors as ornamental garden plants.

They can be grown outdoors or indoors in pots or containers. If they are grown outdoors, they should be given partial shade and protection from cold winds because they are vulnerable to frost damage.

However, this makes them difficult to grow in colder climates.

For these reasons, blue torch cacti are best grown indoors. In temperate climates where there is no danger of frost damage and growing them outdoors is practical, it will produce flowering spikes up to 10 feet tall and spines that range from 3 inches long to more than a foot long.

Pilosocereus azureus propagation

Pilosocereus azureus

To propagate Pilosocereus azureus, remove a stem with several nodes from the main plant. Cut the stem into 3-4 inch sections and allow them to callous over for a few days. Once the ends have calloused, insert them an inch or so into moistened cactus mix or perlite.

Keep the soil moist but not wet and in a warm, bright location out of direct sunlight. New roots will form in 4-8 weeks. When new growth appears at the top of the pot, move it to its own container with a fresh potting medium. If you are rooting more than one stem, separate them by at least two inches before inserting them into their own pots.

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After about 6 months, cut off all the leaves on each of the stems that grew from your original cutting; these leaves may turn yellow if they are root-bound. After 8 months, carefully pull out all but one node on each stem and transplant them into their own containers again with a fresh potting medium.

In 2-3 years your original cutting should be covered in pups (or daughter plants). These can be divided into individual pots as well. It is best to wait until the second year before dividing pups, as this gives them time to establish themselves better.

Pilosocereus azureus care information

Pilosocereus azureus

The Pilosocereus azureus is a columnar cactus that can grow up to 20 feet tall. It is native to Mexico and can be found in the wild in Sonora and Baja California. The blue torch cactus is adapted to living in hot, dry climates and does not need much water to survive.

When watering, make sure to allow the soil to dry out completely between waterings. The blue torch cactus blooms from May to July and produces white flowers that turn yellow with age.

Light requirement

The Pilosocereus azureus requires a lot of light to grow. If you live in an area with little sunlight, you may need to supplement with artificial light. The best way to provide the cactus with the light it needs is to place it in a south-facing window.

You can also purchase grow lights for around $100 and set them up about 2-3 feet away from the plant. Remember that this type of cactus doesn’t like being wet so make sure to keep your plants away from any moisture or water source.

Soil/potting mix

This cactus prefers a well-draining soil or potting mix. A good option is to mix together equal parts of perlite, sand, and cactus potting mix. You can also add in a small amount of sphagnum moss to help hold moisture.

If you’ve transplanted your blue torch cactus from another container, you may need to water it more often at first until the roots have had time to adjust.


The Pilosocereus azureus is succulent, so it does not require much water. In fact, too much water can be detrimental to the plant. The best way to water a blue torch cactus is to let the soil dry out completely before watering again. This plant is native to desert regions, so it is used for infrequent watering.

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When you do water your blue torch cactus, make sure to use room temperature water. Be careful not to overwater this type of cactus as it has very shallow roots and can rot if given too much water.

If you live in an area with more frequent rainfall than what is common for this plant’s natural habitat, then fertilize once or twice per year with a controlled-release fertilizer during the spring and summer months only.


Fertilizing your Pilosocereus azureus is important to maintain its health and vigor. You can use a balanced fertilizer that is low in nitrogen and phosphorus, or you can use a cactus-specific fertilizer.

Apply the fertilizer to the soil around the base of the plant, being careful not to get any on the plant itself. Water the plant thoroughly after applying the fertilizer. Fertilize your blue torch cactus every two to four weeks during its growing season, which is typically from spring to fall.

Fertilizer should be applied sparingly, a little goes a long way! To avoid burning your plant, never fertilize it at night.


The Pilosocereus azureus is a heat-loving plant that thrives in temperatures above 50 degrees Fahrenheit. It can tolerate occasional light frosts, but prolonged exposure to cold weather will damage the plant.

When grown indoors, the blue torch cactus should be kept near a sunny window where it will receive at least six hours of direct sunlight each day. During the summer months, the plant can be moved outdoors to a sunny location.


The blue torch cactus prefers warm climates and high humidity levels. However, it is tolerant of a wide range of conditions and can even survive in drought-like conditions.

The ideal humidity range forPilosocereus azureus is 70 to 80%. In the wild, they tend to grow near water sources or in shady areas. Blue torch cacti prefer some shade during the day but should be kept out of direct sunlight.

They require bright light at night so don’t place them too close to a window or other light source if you live somewhere with long winters.

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The Pilosocereus azureus is a columnar cactus that can grow up to 20 feet tall. It is native to Mexico and can be found in the wild in the states of Tamaulipas, Nuevo Leon, and Coahuila. The blue torch cactus is easily recognizable by its bright blue color and prominent spines.

When pruning this cactus, be sure to wear gloves and long sleeves to protect your skin from sharp spines. Cut off dead or damaged tissue with a clean pair of scissors or garden shears.

If you have any questions about whether or not the plant needs to be trimmed, always err on the side of caution and trim it back if necessary. Trimming will help promote new growth for the following year’s blooms.

When to repot

You’ll know it’s time to repot your Pilosocereus azureus when the roots start to come out of the drainage holes, or if the plant is top-heavy and falling over. If you see any of these signs, it’s time to give your cactus some more room to grow!

Place the pot in a shallow tray filled with pebbles to keep it from disturbing the roots as you remove it from its current container. A new pot should have drain holes at the bottom and be a little bit bigger than your old one.

Fill with loose, well-draining soil mix such as cactus mix, then set the plant inside of it. When planting a succulent that has been potted for several years, break up the root ball into smaller pieces and trim off any dried-out roots before planting.

Gently pat down the soil around the base of the plant so that there are no air pockets – air pockets can lead to rot.

Once planted, water Pilosocereus azureus thoroughly so that all of the soil becomes moist but not saturated with water; don’t forget to place it back in an area where it will get plenty of sunlight and indirect light for about 12 hours each day.

Dormancy/Winter rest

As the weather cools and days grow shorter, many cacti enter into a period of dormancy. This is a natural process in which the plant conserves its energy for the winter months ahead.

For Pilosocereus azureus, dormancy typically lasts from October to March. During this time, the cactus will not grow or bloom. However, it is important to provide some basic care to ensure that your plant remains healthy during this rest period.

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Water the cactus sparingly and avoid fertilizing it. When you do water your plant, be sure to water thoroughly until moisture comes out of the potting mix at the bottom of the pot. Avoid letting any part of the soil dry out completely.

Growth rate

Pilosocereus azureus

The growth rate of the Pilosocereus azureus is rather slow. However, with the right care, this cactus can grow to be quite large. When watering, be sure to only give the cactus a little bit of water as too much can cause the plant to rot.

The best time to water is in the morning so that the cactus has all day to dry out. Be sure to fertilize your cactus every few months with a high-quality cactus fertilizer.


Pilosocereus azureus is not toxic and therefore is considered safe around pets and children.

USDA hardiness zones

Pilosocereus azureus thrives in USDA hardiness zones 10-11. It is native to Mexico and can grow up to six feet tall. It is one of the easiest cacti to grow and care for, which makes it a great choice for newbies.

The blue torch cactus produces large clusters of small yellow flowers during the summer months, which attract hummingbirds and other pollinators.

Pests and diseases

The blue torch cactus is susceptible to mealybugs, scale, and root rot. Mealybugs are small, white insects that attack the cactus by sucking the sap from the plant.

Scale are small brown or black insects that attach themselves to the cactus and feed on the plant’s juices. Root rot is a disease caused by fungi that attacks the roots of the cactus, causing them to rot.

In order to prevent this disease, keep the soil around the base of the plant well-drained. Also, make sure that there is good air circulation near the base of the plant so it doesn’t sit in wet soil for long periods of time.