Euphorbia tirucalli or Pencil cactus is a succulent native to Africa that features pencil-thin stems growing in an upright and bushy pattern.
The tips of the stems are often orange or pink, especially on new growths, which adds aesthetic and architectural value to the plant.
The Pencil cactus is relatively easy to grow indoors, so if you’re considering it as a houseplant, my plant care recommendations below will come handy to you.
Size & Growth
As a tall-growing succulent, the Euphorbia tirucalli can reach the ceiling indoors if conditions are favorable and it’s allowed to grow. While the height it can reach indoors is around 6 feet, outdoors the plant grows much taller, reaching 30 feet even.
Because it can grow so tall and it’s an unmistakable presence in your home, you must be cautious with this plant because its milky sap can cause severe allergic reactions and rashes on mucous membranes.
If you have small children or pets inside the house, you should reconsider whether you want to keep this potentially dangerous plant around.
Even when pruning or handling the plant, you should always wear protective gloves. Rashes, blisters, swelling or allergic reactions are to be expected upon contact with the sap.
Because these plants are accustomed to direct light in their natural habitat, you must thrive to recreate the same light conditions.
When grown indoors, place the plant in a sunny spot in your home for maximum light exposure and growth.
Don’t even try to experiment with low light conditions. The Pencil cactus will simply not tolerate it and do poorly and show signs of etiolation.
Place near a window with southern exposure to ensure your Pencil cactus will receive adequate light during the day.
The Pencil cactus has adapted to growing in arid, water deprived environments and it’s good at storing water in its stems. Therefore, don’t worry about forgetting to water this plant.
You’re much more likely to cause damage by overwatering it rather than forgetting to water it now and then.
It’s fine to water this plant every 2-3 weeks in the summer and withhold water altogether during the winter months.
Overwatering will easily cause root rot issues, especially if your Pencil cactus is not planted in a well-draining potting mix.
Therefore, besides allowing the potting mix to become dry before watering, you should also choose a potting mix that’s designed to keep succulents and cacti happy.
Gritty, fast-draining soil that doesn’t become compacted is ideal for the Pencil cactus. You can plant in any potting mix that’s specially formulated for succulents and cacti.
These special mixes can already contain fertilizer for succulents and cacti, so you may not even have to bother with that.
Although your Pencil cactus might get by even in regular potting soil, I highly advise against it.
Regular potting soil is simply too heavy and prone to compaction and water retention, which can easily lead to root rot issues if water is allowed to pool at the roots.
Temperature & Humidity
Considering that it’s a plant native to Africa and more arid regions of India, it’s no surprise that your Pencil cactus will prefer a warm and dry environment.
Temperatures should be above 65 F. Anything below will detrimentally affect the development and well-being of your plant.
Pencil cacti kept outdoors during the summer, should be taken indoors in the fall. Even when indoors over the winter, you should still be careful to protect your Pencil cactus from cold drafts or sudden changes in temperature.
While hardy, it’s not a cold-resistant plant. It’s hardy in warm, arid climates.
If your potting mix already contains fertilizer, you don’t need to regularly fertilize your Pencil cactus. Even if the formulation of the potting mix is without any added fertilizer, you only need to fertilize this plant in the spring.
If you find a good fertilizer formulated for succulents or cacti, you can use that at the dose and frequency recommended on the label. Usually, there’s no need to fertilize these plants more often than once a month.
Slow release fertilizers are also an option, use these when planting or repotting the Pencil cactus. They’ll usually last for about 6 months.
Potting & Repotting
The best pots for cacti and succulents are unglazed terracotta pots. Because of their porous structure they can absorb excess moisture easily, preventing the much-dreaded root rot when used in combination with well-draining potting mix.
Usually, when growing Pencil cacti, repotting is not in the books for at least 2-3 years. These plants don’t mind being pot-bound, and even when they’re transferred it’s best to get a pot that’s just one or two sizes bigger.
When repotting, check the roots for damage or disease. Transfer your Pencil cacti to a new pot only in the spring or summer, when the plant is at its strongest.
How to Propagate Pencil Cactus?
Although it’s relatively easy to propagate the Pencil cactus, the difficulty stems from the fact that the milky sap of the plant can cause severe skin problems.
When taking stem cuttings, make sure to wear protective gloves and some suggest wearing protective goggles as well just to make sure you don’t accidentally rub your eyes with your hands.
The easiest way to harvest stem cuttings is to cut them with a razor blade. Allow the cuttings to dry and form a callus, and then place in a soiless medium.
Mist the potting mix and keep it moist but not wet to stimulate root formation.
If you’re looking for a tall-growing, interestingly shaped succulent that carries with it a bit of danger, the Pencil cactus might be something to consider.
Although it’s a plant that’s off limits to pets and children, if not applicable, you can grow this plant indoors or out, when and where the weather allows it.
Don’t forget to wear protective gloves when handling it and give it plenty of sunshine so it can grow and develop into the bushy plant it’s supposed to be.