The blue torch cactus is becoming rarer and rarer as time goes on. As such, it’s important to learn how to properly care for it. With this guide, you can help it thrive so that you can enjoy your unique cactus for years!
To successfully care for a blue torch cactus, it must be grown at 80–90°F, given 6 hours of sun daily, planted in well-drained soil with 50% grit, and watered twice a month. Liquid fertilizer with phosphorus can be given twice a year during growing seasons.
There is a Swedish proverb that says the well-loved child has many names. For this cactus, this is certainly true! Commonly known as the blue columnar cactus, the wooly blue torch, and the wooly blue spirals, this cactus has fascinated people for years.
Check out this quick summary of everything the blue torch cactus needs to flourish.
Well-drained mix made of 50% pumice, 30% cactus soil or coco coir, and 20% vermicast
Water twice a month and allow the soil to fully dry before watering. Reduce water in the winter
6 hours of full sun per day
80°F to 90°F
40 to 60%
Twice a year with phosphorus-rich liquid fertilizer at half strength or less
Keep scrolling to learn more details about each of these factors!
A blue torch cactus needs soil that also contains about 50% pumice with cactus soil, or 30% coco coir, and 20% vermicast. The inclusion of coarse components such as perlite and lava stone further improves drainage.
Like most other cacti, the blue torch cactus needs to be grown in a gritty and well-draining growing medium. If the cactus is well-tended, its narrow stem should grow up to 2 feet per year.
Regular potting soil is not recommended as this can hold too much water than the cactus can handle. Cactus soil should be used instead.
Whatever growing mix you decide to use, at least 50% should consist of grit or gravel. This will help increase drainage and protect the cactus from getting wet feet!
Avoid placing rocks at the bottom of the pots. This has been disproven to be good for drainage and can even be harmful to plants.
Learn more about when and when not to put rocks at the bottom of pots.
Once your blue cactus torch has been given the right soil, you can expect to see it grow to 1–2 feet inside a container. In the ground, however, this cactus can reach over 10 feet (3.05 m) tall!
The blue torch cactus can be watered 2 times a month and must be allowed to dry completely before the next watering. Reduce or halt watering completely in the winter to prevent rot.
Because it is drought-tolerant, the blue torch cactus does not need to be watered daily. It only needs to be watered infrequently once established.
Never leave it in standing water. It grows primarily in seasonally dry environments and is used to such conditions.
However, it will appreciate regular watering during hot summers and will thrive when watered 1–2 times a month. If your blue torch cactus is kept outside and receives a heavy soaking from rain, you can skip watering it for the next 3 weeks.
How much water your cactus will need will always depend on environmental factors such as lighting and humidity.
A good general rule to follow though, is to cut back on watering during the winter. Just like other cacti, the blue torch cactus prefers to rest during the winter and does not require as much moisture.
Blue torch cacti require a minimum of 6 hours of direct sun per day to help maintain its coloration. Their stems will turn green if the plant is not receiving adequate light and must be given increased sun exposure.
The blue pigments in the blue torch cactus become more and more prominent with age and sun.
It’s one of the few columnar cacti with vivid blue stems and should be light sky blue when placed in direct sun. If it does not receive enough light, it will eventually lose this color and fade back to green!
While it will still be alive, it will no longer be as colorful. To solve this, put it in a sunnier spot. Doing so will make the blue pigments gradually return over the next few months.
Provide the blue torch cactus with at least 6 hours of full sun to help keep it happy and help maintain its lovely blue hue. Newly bought blue torch cacti should be acclimated and allowed to gradually adjust to its new lighting.
Temperatures between 80–90°F are suitable for blue torch cacti and will ensure consistent growth. It does not thrive when kept under 50°F. Hence, it must be brought indoors during the winter or protected to prevent frost damage.
This sun-loving cactus can tolerate higher temperatures than most other plants, so don’t be afraid to plant it in hotter climates.
Having said though, if you worry about excessively hot weather, the cactus can always be moved to more shaded areas. Do this if it starts to show signs of sunburn and darkened patches on the stem.
A blue torch cactus is not very picky and can grow in temperatures up to 90°F.
In case you regularly have frosts below 50°F or 10°C, it’s best to keep the cactus as a potted plant or grow it strictly indoors.
Because while it can tolerate temperatures much lower than this, the cold can still be damaging. Your blue torch cactus is likely to rot if it is not kept dry and properly ventilated.
The blue torch cactus grows well in typical household humidity between 40–60%. But it can still grow in even lower humidity levels.
If you live in an area with low humidity, you’ll be happy to hear that buying an extra humidifier for this cactus is not necessary. Plus, your wallet will thank you for it!
High humidity isn’t an essential factor when caring for blue torch cacti, since many desert cacti like these live in environments with less than 40% humidity.
Indoor cacti should grow just fine at average or moderate household humidity levels. Check the humidity in specific rooms and areas using a hygrometer. But again, this isn’t required.
Additionally, it’s important to note that misting does not make any reliable difference in raising the humidity. If anything, it might harm your cactus in the long run.
Explore more in this article on “Should Cactus Be Misted?”.
Misting can cause stem rot in cacti and can even lead to fungal disease by allowing excess moisture to sit on the surface of the cactus. Therefore, it’s best to avoid misting your blue torch cactus.
A blue torch cactus is not a heavy feeder, only needing fertilizing twice a year. Excessive fertilizer can burn cactus roots. Avoid granular fertilizer. Feed the cactus liquid fertilizer rich with phosphorus in the spring and summer.
It might be tempting to shower this rare cactus with plenty of nutrients to help it grow, but this can be more harmful than you think!
Blue torch cacti have thin and fibrous roots that have adapted to collect as much water as they can in shallow soil. For this reason, the roots are highly sensitive, making this cactus more susceptible to fertilizer burn.
Caring for this cactus is relatively easy compared to other plants, as it does not need to be fertilized more than twice a year.
A phosphorus-rich liquid fertilizer can be diluted and given at half strength during spring or summer as it’s still producing new growth.
Slow-release fertilizer might be more convenient but can quickly overwhelm the cactus over time, so you may wish to avoid it.
Learn more and know the pros and cons of liquid vs granular fertilizer.
When in doubt, fertilizer can be given in weaker or smaller amounts.
Unlike the blue torch cactus, many succulents can turn blue as a sign of etiolation or a lack of light exposure. This blue discoloration in succulents can be maintained but this will eventually kill the plant.
After learning how to care for the blue torch cactus, you might be wondering why cacti and succulents turn blue, to begin with.
Typically, if you see your succulents turning blue and growing longer stems with fewer leaves, this could mean they are etiolated.
When there is not enough sun for the plant, this can result in etiolation. Deprived of light, these succulents will desperately attempt to grow towards the nearest light source, stretching themselves out in the process.
Without this much-needed sun, chlorophyll production will eventually dwindle, leaving the plant to look more pale and blue. Succulents that turn blue for this reason can be kept for a short amount of time. But it can’t live like this for long, and will soon die.
Now, what about the blue torch cactus? It becomes bluer as it ages and is exposed to more sun. It seems to be quite the opposite compared to a majority of succulents.
Studies for this cactus are rarer than the plant itself. It’s not clearly explained why this specimen produces such vibrant blue pigments in the sun.
But we do know that this isn’t uncommon in nature, and that there are other blue succulents!
The echeveria blue bird is another common succulent that grows blue leaves and thrives with only 4 hours of full sun. Propagation can be done by cutting mature plants in half and allowing them to take root.
The following succulents, just like the beloved blue torch cactus, are naturally blue. One of the most common blue succulents available is the blue echeveria.
Unlike other succulents, its leaves do not only turn blue when it lacks light. The echeveria blue bird naturally produces blue-green leaves and needs just a few hours of direct sun to help maintain its color.
Additionally, these succulents can easily be propagated by cutting mature plants in half, removing a few leaves from the bottom section, and allowing it to grow new leaves. The top half of the plant can be left alone to develop roots.
After several weeks, these cuttings will eventually take root and produce more blue echeveria!
This lovely blue color should stay until the plant is severely stressed, in which case, it may turn red.
Find out why cactus plants turn red and how to treat them.
Do blue torch cacti bloom flowers?
Flower buds are usually only seen on blue torch cactus after it has fully matured and is at least 3 feet (0.91 m) high. The flower buds emerge from white tufts of hair on the cactus and will grow to be white flowers shaped like funnels. These blossoms frequently open only during the night.
Are blue torch cacti toxic?
The blue torch cactus is not toxic if consumed and is safe for pets and children. Golden spines can be found on the stem of the cactus, however, and are extremely painful to touch. Keep this cactus out of children’s reach. Only handle the blue torch cactus using gloves.
Is the blue torch cactus rare?
Although popular for its ornamental value, the blue torch cactus is endemic to Rio, Brazil and is unfortunately being threatened by habitat loss. Because of this, the cactus can be difficult to find in plant centers and can be extremely expensive.
A blue torch cactus is not a high-maintenance plant. However, growing this cactus requires exposure to 6 hours of full sun per day and being planted in a potting mix made of 50% grit for optimum drainage.
The cactus should only be watered every two weeks once the soil is completely dry. Avoid watering this plant in the winter when it is dormant. Feed the blue torch cactus liquid phosphorus-rich fertilizer at half strength at least once a year to help support growth without burning the roots.