Gardening 101: Pencil Cactus

Pencil Cactus, Euphorbia tirucalli: ‘Sticks on Fire’

I am not usually a person who throws caution to the wind, but despite the numerous warnings about the toxicity of euphorbia’s latex sap, I still admire and use this striking plant in many of my container designs.

Please keep reading to learn why you should still plant pencil cactus (carefully, of course).

Native to arid South Africa and India, pencil cactus is actually a euphorbia, thus making it a succulent and not a true cactus despite the name. There are thousands of euphorbias, and like all of them, the pencil cactus has milky white latex sap that is released when the plant is injured. This sap can be strongly irritating to some and hard to remove even with soap.

I actually get the sap on my skin from time to time despite my safety attempts and don’t find the sap irritating, but there are countless wicked accounts of the opposite. If there is eye contact, blindness can occur, and ingestion of the sap can be fatal. Now I know this sounds like a doomsday scenario, but if caution is exercised and gloves and sunglasses or other eyewear are donned, then there is no need to shun this beautiful plant.

This euphorbia got its nickname ‘Sticks on Fire’ for a reason. Numerous slender stems, resembling small pencils or sticks, grow from the base, and during the cooler months they glow superbly in vivid shades of pink, orange, and yellow when grown in bright sun. The colors are utterly stunning and make you forget the warnings.

Pencil cactus is easy to grow if three things are provided: high light, low water, and gritty soil. Tip: This plant is perfect for travelers or people who sometimes forget they have houseplants.

Cheat Sheet

• This colorful succulent is the ideal specimen for containers providing a striking silhouette. In its natural habitat, pencil cactus can soar to 30 feet, and in a pot it can reach six feet under ideal conditions.
• Plant pencil cactus with Sedum ‘Angelina’ to highlight the bright chartreuse tones, or plant with Sedum ‘Firestorm’ or Crassula ‘Campfire’, whose red and orange margins pick up the euphorbia’s bright hues.
• Pencil cactus is an excellent choice for drought-tolerant, succulent seaside gardens where temperatures don’t dip below 25 degrees Fahrenheit. Looks lovely with aloes and agaves.

Keep It Alive

• Outdoors, grow pencil cactus in full sun. Indoors, place it on a sunny, warm windowsill that receives a southern or western exposure. It also is happy living in a greenhouse.
• Provide immaculate drainage for pencil cactus. Bagged cactus soil is encouraged.
• Water every two weeks and less in the winter, and as with most succulents, it’s better to let pencil cacti dry out than to drown it or risk rotted roots.
• Fertilizing is not urgent, but if you want, try a balanced liquid houseplant food, feed pencil cactus once a year in the spring.
• Be cautious when pruning any dead stems to avoid skin contact with the sap.

For more growing tips, see Pencil Cactus: A Field Guide to Planting, Care & Design in our Garden Design 101 plant guides. Learn more about our favorite succulents:

• Succulents & Cacti 101: A Guide to Growing, Care & Design
• Agave: A Field Guide
• Gardening 101: Christmas Cactus