Last updated on August 25th, 2023 at 11:45 am
If you’re searching for a unique cactus to add to your collection, Pilosocereus pachycladus, also known as the blue columnar cactus, wooly blue torch, blue cactus plant, or tall cactus plant, might be just what you’re looking for. Native to the deserts of Arizona and New Mexico, this cactus typically grows to be about three feet tall (though it can sometimes grow as tall as six feet) and has four inch-long, bright blue spines.
If you live in an area with high humidity or wet weather, pilosocereus pachycladus may be right up your alley as an addition to your plant collection. These beautiful plants are unique because they grow with long, straight stems rather than the typical round ones that most cacti have.
Fortunately, you can easily grow your own blue columnar cactus if you have the right conditions and know exactly what you’re doing. In this guide, I’ll cover how to plant and care for a blue columnar cactus from start to finish so that you can enjoy this unique and beautiful plant in your home or garden.
Origin and distribution
Pilosocereus pachycladus is native to southern Mexico, Guatemala, and Belize. It has naturalized in Costa Rica and Panama. It is found in tropical deciduous forest on hillsides and stream banks, often at elevations of 1000–1400 m (3000–4500 ft).
This columnar cactus grows slowly, producing a tall central stem with branches that spread out to about 2 m across (6 ft) after 20 years or so. Flowering is not very showy; it usually produces no more than two flowers per branch per year. Flowers are pale green with tinges of pink or white and are borne from November through April. As the plant matures, the needles turn blue-green or grayish blue.
Pilosocereus pachycladus prefers to grow in hot climates, even tolerating occasional frost during the winter months when temperatures don’t go below -5°C (23°F). In gardens where it can be exposed to direct sunlight all day long, this species develops strong stems up to 10 cm thick that have small leaf spines along their length.
Pilosocereus pachycladus propagation
To propagate a Pilosocereus pachycladus is fairly easy, though in general all cacti should be propagated from seed, not from cuttings. To do so, collect 1-2 seeds and soak them overnight in lukewarm water.
Place each seed on its own paper towel and enclose it in plastic to create a mini greenhouse for each one. Allow your seeds to germinate over about 6 weeks at which point you can plant them separately into a well-drained soil mix.
Keep the soil moist but never wet; this will encourage root growth and help prevent rotting of the new plants.
You will know when your new blue columnar cactus has emerged from the soil by two signs: firstly, there will be a hole left in the surface of the dirt where it was planted.
Secondly, that hole will fill with water as roots take hold of their new environment.
If these two conditions are met then congratulations! Your blue columnacactus is ready to live outdoors!
Pilosocereus pachycladus propagation from cuttings
If you’d like to propagate your pilosocereus pachycladus from cuttings, you can divide or segment your plants, as described above. You can also take cuttings of them to grow a plant identical to its mother.
To do so, wait until night when there is no new growth developing on it. Take a sharp knife and remove 3-4 healthy segments about 1 in diameter from its sides.
Plant the cutting deeply into potting soil. Keep an eye on the soil level as this species does not tolerate sitting in water for too long. Eventually, roots will form at the base of the cutting and then go down into the soil.
Once that happens, it’s time to transplant the cutting back into the ground in a location where it’ll receive plenty of sunlight. Be sure to monitor this blue columnar cactus closely because any frost or low temperatures could kill it!
Pilosocereus pachycladus care information
An important aspect of pilosocereus pachycladus gardening is giving them what they need to thrive. Start by choosing a place in your home that gets plenty of sunlight, at least eight hours a day.
Light requirement
Columnar cacti grow best in full sun. Provide a minimum of four hours of direct sunlight per day for optimal growth. While your cactus may survive and even thrive under low light conditions, its growth rate will be reduced significantly.
Full sunlight is recommended to ensure maximum exposure to vitamins D3 and A produced by UVB radiation in direct sunlight, which are important for overall health.
Soil/potting mix
Pilosocereus pachycladus are tall, blue-green plants that can grow up to 10 feet tall in a greenhouse.
They require sandy soil with a pH between 5.5 and 6.5, a sunny location and full or partial sunlight at least six hours per day. It’s best to use commercial soil mixes or potting mixes rather than growing them in pure sand because they have shallow root systems.
As an added benefit, pilosocereus pachycladus has roots that are long and fibrous, and do not require special pots—just a good potting mix and a tall cactus plant planter.
When choosing your blue columnar cactus soil, look for something with slightly more clay than sand; pilosocereus pachycladus roots prefer to grow in moist soil but do not like to sit in wet environments for extended periods of time.
Watering
Pilosocereus pachycladus requires a little more attention to watering than other cacti. Only water when its soil is completely dry. It’s also important to make sure that it never sits in water, as standing water can rot its roots.
As such, you should use a saucer for your plant so that if you forget to empty it, excess water will simply collect in it instead of soaking into your plant’s soil and damaging its root system.
Fertilizer
To grow an optimal pilosocereus pachycladus, use about 1/4 of a cup of fertilizer around 3 feet from where you’ll be planting. Feed your new baby cactus lightly each month or two to keep it healthy. Give them at least a few hours of sun daily and make sure they have enough water in the soil.
If there is not enough water in the soil, the blue color will slowly disappear and they will turn green.
Pilosocereus pachycladus are tall cactus plants with large blue stems that can reach over 6ft tall. They come in many different colors including white, red, and pink but the blue color is what makes these cacti so special.
Temperature
This plant is sensitive to temperature. It cannot tolerate freezing conditions, although it can survive very cold weather. If you live in an area where temperatures dip below freezing, it’s best to bring your blue columnar cactus indoors for its safety.
Be sure to move it back outside as soon as possible once winter is over. Most Pilosocereus prefer tropical areas with year-round warm weather and indirect sunlight.
During winter, temperatures can drop to a low of about 0°C (32°F) in their natural habitat and over 30°C (86°F) in summer. In these conditions, blue cactus plants flower all year round and prefer full sun exposure, with moderate watering.
They are hardy plants that prefer sandy soil but are tolerant of light shade. To propagate blue cactus plant seeds, plant them at 5 cm deep with only their tips showing above ground level.
Humidity
It’s easy to forget about humidity when planning for cacti, but humidity is a key factor in determining how your plants will grow. Humidity requirements vary based on species and variety, but as a general rule of thumb, Pilosocereus pachycladus like higher levels of humidity (around 50-70% relative humidity) than many other types of houseplants.
Pruning
One of many techniques used to control columnar cacti, pruning involves cutting off parts of a mature cactus to encourage new growth. Pruning can be done at any time of year; winter is usually recommended because temperatures are low and less water is needed than in other seasons.
A disadvantage of pruning columnar cacti during cold months is that it will take longer for any wounds to heal since they can’t breathe as well.
When to repot
If your pilosocereus pachycladus has a trunk of about one inch, then it’s time to transplant it into a new pot that’s an inch or two wider than its original container. After repotting, don’t water for at least four days, and then only lightly, until new roots have grown.
If you keep your plant in direct sunlight, be careful not to overwater it; these plants prefer indirect light and moist soil. They need more air circulation, too, so they should never be placed near a window with closed curtains. Allow the surface of the soil to dry out between watering sessions.
Dormancy/Winter rest
This perennial cactus should be planted in well-drained soil, with a fair amount of organic matter. It will survive temperatures down to -20 degrees Celsius, so can be grown outdoors in cooler parts of North America (zone 6 and higher). Outdoors, it does not have to worry about droughts or freezes; indoors, however, water may be limited from late fall through early spring.
Make sure to never let its soil dry out completely and give it plenty of indirect light when indoors. In late fall or early spring, before frost is expected, you can bring your blue columnar cactus inside for dormancy. Water regularly until late fall or early spring and then allow its soil to dry out completely over winter.
Pilosocereus pachycladus flower & fragrance
Pilosocereus pachycladus produce small white flowers at the tips of their stems in spring and summer. These beautiful fragrant blossoms are pollinated by night-flying moths. If you’d like to grow a columnar cactus yourself, be sure to check if it is suitable for growing indoors, outdoors or in a greenhouse.
Growth rate
Pilosocereus is a slow-growing, columnar cactus that may reach a height of up to 10 feet tall. In ideal conditions, you can expect it to grow about one foot every year.
It’s possible for this cactus to produce branches from the base in response to extreme drought or severe frost. If the stem breaks, it will not regenerate and the plant will die if the stem is broken at or below ground level.
It prefers bright light, so make sure you put your plant in an area with plenty of sunlight if possible.
Toxicity
Although Pilosocereus pachycladus is non-toxic, there are several reports that say eating it may cause nausea, vomiting and drowsiness. When ingested by farm animals it may cause diarrhea and increased urination.
As always though you should consult a doctor if you or your pet have ingested any part of any plant (just in case).
USDA hardiness zones
Pilosocereus pachycladus thrives in USDA hardiness zones 8-10, and will typically grow up to 10 feet tall. It can take years for this plant to reach its full height, so make sure you are prepared for a long-term commitment before adding it to your garden.
These cacti can be planted both indoors and outdoors, but it is important that they have plenty of room because they have a voracious appetite for water. There are many varieties of these cacti available at nurseries or online, so do some research before you buy!
Pests and diseases
Like most cacti, pilosocereus pachycladus is susceptible to powdery mildew, which can appear as white or grayish spots on your plant’s leaves and stems.
Powdery mildew spreads rapidly in hot, humid conditions, so keep an eye out for any signs of mold or fungus on your cactus. In severe cases of powdery mildew infection, you might notice lesions appearing on stems or trunk; remove these tissues with a sharp knife and dispose of them.
