Tall bright blue trunk, white flowers, golden and orange spikes along the ribs are the distinct characteristics that make Pilosocereus Azureus a must-have in every cacti collection.
This pillar-type cactus turns bluer as it ages. At full maturity, it displays a greyish-blue tone earning it the name Blue Torch Cactus.
It has become an instant favorite for both landscapers and hobbyists because of the contrast it creates in landscapes, desert gardens, and even containers.
It belongs to the Pilosocereus family that is native to Mexico, Brazil, and the Caribbean. They can grow up to 10 to 30-feet tall and they’re known locally as Tree Cactus. Mature Pilosocereus Azureus display spectacular white blooms from April to July.
Nor do you need to plant directly in the ground to enjoy this blue beauty. Mine is potted in a 10” planter, sitting by my living room window sill for a couple of years now!
Here’s how to take care of your Blue Torch Cactus.
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Pilosocereus Azureus “Blue Torch Cactus” Care
The Blue Torch Cactus enjoys a well-draining soil mix. For best results, use a gritty medium that provides very good drainage. This Cactus grows well in hardiness zones 9b-11b and loves tropical temperatures. Don’t leave it alone in the freezing cold during winter, though. I suggest using burlap. Burlap protects the cacti while allowing air circulation to avoid winter rot and damage.
A plant that thrives in arid landscapes, Blue Torch cacti would grow well in a gritty medium that has very good drainage.
You can pick up cacti soil mix from your local garden center or you can create your own soil mix. You can take 1 part potting soil or compost, 2 parts pumice or perlite, 1 part sand or gravel.
Test it out and check if water goes right through your medium before planting your Blue Torch Cactus. If it’s having a difficult time draining, you can always add more pumice, perlite, sand, or gravel. The goal is to make it gritty enough for air circulation and water drainage but it should have enough body to hold your cacti.
Pilosocereus cactus also prefers a slightly acidic to a near-neutral soil pH (6.1 – 7.3). Adding coffee grounds occasionally will help your Blue Torch thrive.
Pilosocereus Azureus is a sun-loving cactus. In fact, they turn bluer and their spikes become golden orange in full sun. That’s 8 hours of direct sun without worrying about the nasty cacti sunburns!
However, if you’re growing your Blue Torch Cactus indoors, look for south or west-facing window to maximize sun exposure.
If you don’t have a south or west-facing window, place it in the sunniest part of your house. A good 4-6 hours of indoor sunbathing would be okay.
Here are a few telltale signs that your Blue Torch Cactus is not receiving enough light:
- Etiolation – Just like other columnar cacti, Pilosocereus Azureus will stretch and follow the light. You’ll observe thinning of top growth that disfigures its upright trunk.
- Discoloration – Your Blue Torch Cactus won’t longer have its sought-after blue hue. Others fade, some turn green.
- Root rot – One of the major causes of root rot is wet roots. This happens when the roots sit on wet soil for a long period of time. Exposure to the sun helps the soil dry.
When moving your Blue Torch Cactus from your home to your lawn or outdoor area, you have to acclimate it to avoid sunburn. Immediately placing your cactus outside and leaving it there to adjust on its own can cause the plant to die.
To help acclimatize your cactus, slowly introduce it outdoors by putting it outside for a few hours each day.
For the first week, you can place it in a shaded area after 2-3 hours of morning sun. Another week of partial sun exposure and then direct sun.
When it comes to watering Pilosocereus Azureus in a controlled environment like a landscape of planters, you need to remember one most important thing: water only when the soil is dry.
You can use a soil moisture meter. These are devices that measure the volumetric water content in the soil. This can be bought online and some garden centers have them on their shelves as well.
If you can’t get a hold of a soil moisture meter, you can simply use a stick or a toothpick or stick your finger on the soil. If it comes up muddy or wet, check again tomorrow or the next day.
Some suggest keeping your Blue Torch dry during the winter but you can give it a few drinks especially when it’s getting soft and starting to wrinkle. It actively grows during summer so give it a little bit more water.
Again, it should drain well and it should not sit on water from the drainage plate.
A native in South America and the Caribbean, the Blue Torch Cactus thrives well in warm temperatures, tropical and arid climates. It is hardy in zones 9b-11b. It can tolerate temperatures up to 70°F – 80°F and hardy to 30°F.
It should be protected in winter. You can cover the cactus in burlap, frost blankets, or bed sheets. These keep it from scarring and fungal rot caused by the drop in temperature and keeps it away from moisture.
A good practice to help your Blue Torch Cactus survive a harsh winter is to condition it to adjust as early as late fall. Remember that when the temperature drops, it becomes dormant. So you can reduce watering and stop fertilizing come November.
If you decide to uproot the plant and move it indoors, wrap it with cloth or newspaper and wear gloves. Although the spikes are short and not poisonous, they can be sharp and dangerous. While indoors, it should be placed in an area away from your pets and children.
Pilosocereus Azureus can be identified as a semi-tropical cactus since it grows abundantly in the Caribbean and Brazil. The humidity in its native environment ranges from 40% all the way to 70%. This makes the Blue Torch Cactus tolerant to humid environments with good airflow.
However, don’t get disappointed if you live in an area that belongs to the dryer end of the spectrum.
Blue Torch Cacti grow well in desert-like conditions. You can provide more water but see to it that it’s not getting waterlogged.
A good indicator that Pilosocereus Azureus is getting the moisture and water it needs is by pinching it gently. The body should be firm. If it’s getting soft and bouncy, give it a drink.
Water around the pot and not directly on the plant to prevent rot. This method also allows the roots to spread out and provide more anchorage to the plant.
Pilosocereus Azureus doesn’t need much fertilizing because it is already a fast grower. I know some hobbyists who own the bluest and healthiest Pilosocereus Azureus who never fertilized theirs.
The secret is to add compost or vermicast on your medium and repot every 2 years to replenish the soil nutrients. If you’re going to use fertilizers use a complete time-release fertilizer.
Time-release fertilizers release small and consistent amounts of nutrients over a period of time. Using it prevents fertilizer burn that can cause discoloration or root damage.
You can apply at the beginning of the year or during summer on its growing period.
The easiest way to propagate a Blue Torch Cactus is with cuttings.
Use a sterile knife to cut the top part of your mature Pilosocereus Azureus. Place it in a shaded area for 7-12 days until the “wound” is dry. Stick it to your medium and do not water for another 5 days. Watering it immediately will cause it to rot.
When it’s time to water your plant, water only around the edges of the pot. Increase watering when the plant has fully rooted. You can check by giving the plant cutting a soft tug. Resistance means that it has already developed roots.
To make sure that your cutting will develop roots, you can apply a rooting agent or cinnamon. Cinnamon is a cheaper, natural option and it also has antifungal properties.
Aside from applying it to the wounds, you can also sprinkle it lightly to your medium to keep ants and wild mushrooms away!
Pilosocereus Azureus can also be propagated through seeds but it will take years until you will be able to grow one. However, starting from seeds is very rewarding.
To germinate Pilosocereus Azureus seeds, prepare a cactus soil mix. You can buy a ready-made soil mix or make your own.
Fill up half of a plastic container with your soil mix then top it up with fine, strained soil. You can also use a germination tray with a cover. Moisten it preferably using a mister.
Sprinkle the seeds once your pot is prepared. Do not worry about spacing them out, in fact, they germinate better in clusters. Don’t cover them with soil because cactus seeds need light to germinate.
And finally, cover it with plastic wrap and poke some holes or put it inside a ziplock bag.
Place it in a warm area that gets consistent morning light. Mist sparingly and transplant when they’re more than an inch big.
At maturity, it also produces babies or branches off from its base. You can separate it and plant it in another container but they also look good as a cluster.
The Blue Torch Cactus is an upright, columnar cactus with short golden and orange spikes.
They’re very versatile cacti because they do well in both dry and humid conditions as long as they get enough direct sunlight and gritty soil.
They also love warm temperatures and their most active growth period is during the summer. They become dormant during winter.
When planted on the ground, it can grow up to 30-feet tall. When in pots and containers, you need to repot them every now and then to accommodate their fast growth. Keeping them in a small pot restrains their growth.
They also produce tubular, bluish-white flowers that bloom at night when they’re around 60cm tall. The bigger the trunk, the bigger the flower.
When pollinated, these flowers become an edible, deep maroon fleshy fruit that is home to thousands of seeds. Their main pollinators are bats and sphynx months.
Pilosocereus Azureus have extensive, fibrous root systems. They don’t have a taproot thus they don’t penetrate deep into the ground. To keep it happy in a constrained area, you should provide a gritty soil mix so the roots can easily grow around the planter.
Ideally, the planter should be half or twice as small as the plant. This prevents overwatering. They don’t mind getting root-bound and you can replant every 2-3 years.
You can use any kind of planter from plastic to ceramic and glass as long as it has drainage holes. I suggest using a terracotta planter. This kind has very good porosity that helps with airflow. The earthy color also looks great with the plant’s blue skin.
Common problems with Pilosocereus Azureus or “Blue Torch” Cactus
The Blue Torch Cactus shares common enemies with other columnar cacti –mealybugs, scales, and spider mites. The good thing about these is that if detected early, it’s not that difficult to get rid of them.
You don’t really have to obsess over the plants but you should check on them regularly. Look out for white fuzzy insects or brown bumps on the base and top of your Pilosocereus Azureus. These are mealybugs and scales and you can get rid of them using cotton balls or swabs dipped in alcohol.
After removing the individual bugs that are visible, mix 1 part alcohol, a few drops of dishwashing soap, and 4 parts water. Spray it throughout your plant and repeat until you don’t see the bugs anymore.
Spider Mites are a little bit more difficult to detect since they are small. So what you need to check is discoloration, speckling, and fine shimmery webbing. Once you see this, soak the whole plant in water to dislodge the mites and apply neem oil mixed with water using a microfiber cloth or spray.
When spraying your plant, keep it in a shaded area until the mixture dries up to prevent sunburn.
Other common problems are:
- Overfertilization – Overfertilization can cause splitting, discoloration, and brown spotting. Blue Torch Cacti don’t need fertilization. They can grow and thrive with none at all. But if you want to fertilize, use a time-release complete fertilizer once a year.
- Root rot – Root rot is usually caused by fungi and overwatering. To prevent this, start with the basics –gritty soil mix, watering only when the soil is dry, and enough light. When you detect root rot remove it from the soil, cut the infected part, and leave it to dry. You can apply fungicide or cinnamon.
Top tips when growing Pilosocereus Azureus or “Blue Torch” Cactus
- Light, light, and light.
- Acclimatize before fully moving outdoors.
- Use gritty soil mix, it should drain immediately when you water.
- Fertilize with a time-release fertilizer once a year or make the soil rich with compost and vermicast.
- Don’t be heavy-handed when watering. Water only when the soil is dry.
- Use burlap, frost blankets, or bedsheets to protect it during winter.
- Place it in a warm area.
- Use a planter with drainage holes, preferably a terracotta pot for airflow.
- Regularly check for mealybugs, scales, and spider mites.
- Use cinnamon as a rooting hormone and fungicide.
Frequently asked questions about the Blue Torch Cactus
How to differentiate corking from sunburn in my Pilosocereus Azureus?
Corking is part of the natural aging of a cactus and usually develops from the base of the cactus. You’ll observe that the trunk becomes hard and barklike. If you observe browning after increasing sun exposure, that would most likely be sunburn, especially for younger plants.
Should Pilosocereus Azureus necessarily be in full sun?
Pilosocereus Azureus loves the sun. If it doesn’t get its light requirements, the trunk becomes thinner and lighter. But this doesn’t mean that it should only be planted outdoors. Bright south or west-facing area would work well and you can also supplement with a grow light.
Pilosocereus Azureus or “Blue Torch” Cactus is an easy to grow cactus that rewards you with a beautiful blue color for your landscapes, rock gardens, and planters for years! If you’re lucky, you’ll also enjoy its blooms and fruits.
It’s not a high-maintenance plant especially if you’re already used to growing succulents. If you’re new to cacti and succulent care, this guide outlines everything you need to know to keep a Blue Torch Cactus happy and thriving.
Once you get the hang of it, you can add more to your collection. Before you know it, you’ll have a display of cacti and succulents in different forms, shapes, and colors!
Daniel has been a plant enthusiast for over 20 years. He owns hundreds of houseplants and prepares for the chili growing seasons yearly with great anticipation. His favorite plants are plant species in the Araceae family, such as Monstera, Philodendron, and Anthurium. He also loves gardening and is growing hot peppers, tomatoes, and many more vegetables.