The Euphorbia tirucalli is one of over two thousand splendid and diverse plant life within the Euphorbiaceae family. This widespread family of stem succulents has evolved over time to develop characteristics similar to cacti. This clever plant adaptation has enabled this genus to survive in some of the harshest of natural habitats. It’s why they thrive everywhere from the dry, arid landscapes of Southern Africa, Tanzania and Kenya, to India, Indonesia, China and Sri Lanka.
All About Euphorbia tirucalli
Species of Euphorbiaceae range from towering trees (Euphorbia ingens) to the tiny, slow-growing Euphorbia bupleurifolia. In maturity, the latter reaches a height of just 8 inches. More than two thousand Euphorbia species grow throughout temperate areas of the world. In fact, more than 200 are found in Southern Africa alone.
Regardless of their country of origin, they all have one component in common: the toxic latex sap held within their stems and branches. This is just one of the characteristics used to identify them as part of the huge Euphorbiaceae plant family.
The Euphorbia tirucalli—Pencil Cactus plant
The Euphorbia tirucalli is my species of interest today, also known as the “Pencil Cactus” or “Sticks of Fire”. It’s native to Africa’s semi-arid and tropical climates, and is most prolific in North Eastern, Central and Southern Africa. There, this branched, variable succulent readily self-seeds, often reaching heights of up to 30 feet tall.
Its dense, thicket-like structure is regularly used as farm barriers and hedging, hence its common name of “Rubber Hedge Euphorbia”. It’s also used as a cattle feed crops, as well as for extensive commercial cultivation for fuel. This is because it has similar properties to gasoline.
Outside of Africa, this intriguing specimen plant is also found in India, Indonesia, China and the Philippines. As you can see, its origin is extensive.
Suitable Growing Environments for your Euphorbia tirucalli
Due to the temperature environment, the Pencil Cactus is quite a common sight in Sri Lanka. In Tamil, its common name is “Kalli”. The pencil cactus is treated as a frost-tender succulent in cooler climates, perfect for agreenhouse or conservatory. It’s only suitable for outdoor growing in zones 9 to 12.
Many enthusiasts overwinter their Euphorbia tirucalli indoors, then site it outside for the summer months, which seems to work quite well. When grown as a houseplant, you can expect a top height of around 6 – 8 feet tall. Far more manageable than a native 30-foot specimen!
A Fuel-Producing Hydrocarbon Plant
This Euphorbia tirucalli is a hydrocarbon plant. As mentioned, it naturally produces a poisonous latex sap that can be easily converted into a fuel—basically the equivalent of gasoline. Chemist Melvin Calvin cleverly exploited this characteristic and went on to cultivate the species in a bid to commercially produce oil.
He estimated that a single acre could potentially produce 10 to 50 barrels of oil. Unfortunately, Mr. Calvin found he had over-estimated the production levels. As a result, his quest was unsuccessful and the idea was later scrapped.
History of the Euphorbia Tirucalli
The family and genus name “Euphorbia” were given by the Swedish botanist and author Carl Linnaeus back in 1753. It was in honour of one of Linnaeus’ great heroes: “Euphorbus”, who was a fine first century physician to King Juba of Mauritania.
Euphorbus commonly created traditional medicines using plants of the Euphorbia genus. The species name “Tirucalli” was actually taken by Linnaeus from the common name used by the locals of Malabar in Southern India.
This succulent has been used for many years in traditional medicine. It apparently has many medicinal properties, ranging from curing impotence to providing an antidote for snakebites. I wouldn’t recommend testing these claims myself, but I always find it interesting when a toxic substance is supposedly used to heal people.
Euphorbia Tirucalli As a Houseplant
The Euphorbia tirucalli is popular within the houseplant-growing community, not only for its unmistakable smooth, branched form and winter colour, but because it is one very resilient plant. Minimal care, verging on neglect seems to keep the “tirucalli” very happy indeed.
As previously mentioned, you can expect a mature height of between 6 to 8 feet, with a similar sized spread. Its form is spineless, upright and branching. The slender stems are the diameter of a pencil, hence its common name.
Branches are cylindrical and smoothly toothed, only around 8 mm in diameter, and glaucous grey-green in colour. These branches produce small, slender, pendulous branchlets with a rounded crown appearance. New, young growth has a pink hue and very tiny leaves. However, both of these characteristics disappear once the plant reaches maturity.
How Does Euphorbia tirucalli Photosynthesis Take Place?
Due to the wonder of plant adaptation, the pencil cactus uses its spineless, succulent green stems to photosynthesize. This natural adaptation means the plant is able to minimize its surface area and limit excess water losses. It may not be of value when grown indoors, but is fundamental to its wellbeing in its native habitat.
Towards the end of the summer, you’ll notice that cactus will change from glaucous green to yellow-gold.This will progress into the winter month,s turning to ginger, and then deep orange-ed. It’s a truly stunning transformation, providing brightly coloured branches of unexpected winter interest.
The form and fiery shades of this super-succulent are what attracts us to the Euphorbia tirucalli. In contrast, its flowers are rather insipid. However, small clusters of flowers are borne on the crown and inner angles anytime from September through till December.
These attract loads of wildlife, but bees and butterflies are primarily responsible for pollination.
Fruits and Seeds
The fruits are produced from November to December time, in the form of pale green capsules. These are up to 12mm in length, with a pink hue and lots of soft light hairs. The seeds are smooth and dark brown, each around 5mm with a white line around the hilum.
Let’s take a look at how to care for the unmistakable Euphorbia Tirucalli, detailing the perfect growing conditions and resulting in a very happy plant.
Planting the Euphorbia tirucalli
Siting your Plant
Situate your Euphorbia in a position of full sun to part sun, with dappled shade. Ideally a high light and low humidity environment will emulate its natural habitat, which is what we’re really trying to achieve. You’ll get best results indoors in a sunny spot, or outdoors in a conservatory or glass house. Remember this is a frost-tender species and only suitable for outdoor growing (year-round) in zones 9–12.
This colourful succulent is not only easy to care for, it also tolerates dry and rocky soils. It’s drought tolerant, deer and rabbit resistant, and perfect for planting sheltered spot coastal or Mediterranean gardens.
Maintain an ideal minimum temperature of 18 degrees C year-round to keep your Euphorbia tirucalli happy. I always like to keep my houseplants at around 20C, and these seem to get on just fine.
Perfect soil for the Perfect Plant
I recommend using a course, sandy growing medium, with a slightly acidic pH value. A mixture of loam and sharp sand with a touch of perlite should do the trick. Ensure your mix is free-draining, as this cactus doesn’t like to be kept wet.
All Euphorbias contain a milky plant sap within their stems and branches. Even if you brush past these plants, you’re likely to make the plant “bleed”, which could then touch your skin. This species contains 0.4 % rubber and 5.1 % latex: a toxic mixture that often causes adverse reactions in those who don’t wear gloves, or take extra care when handling their plants.
Further complications such as blindness, skin blisters and even fatality can occur if Euphorbias are ingested. When growing wild, this toxic sap acts as a deterrent to many grazing animals. In a home environment, however, keep your plant well away from pets and inquisitive children.
When handling all plants, wear suitable gloves to avoid any potential problems that could otherwise easily be avoided.
Caring for the Euphorbia tirucalli
As with all succulents, the Euphorbia tirucalli likes to be kept on the dry side. It can absorb a lot of water at one time, storing it away and gradually releasing it (when necessary) over the next couple of weeks. Throughout the winter months, you will not need to water at all, as this plant needs a dry winter dormancy.
Water your pencil cactus every two weeks throughout the spring and summer months, when growth is in full swing. Then reduce it early autumn to once every three weeks. Winter dormancy should happen from late October through until the following March.
Fertilizing your Plant
Use a well-diluted liquid fertilizer once every couple of weeks throughout the spring. A succulent fertilizer would be perfect, but only feed when you’ve already watered your plant and the soil is wet.
The Euphorbia tirucalli will grow quite happily in its naturally branching and upright form, with little need for pruning. The key when siting your plant is to plan for potential growth, allowing enough space for it to expand over time.
You can propagate from your Pencil Cactus by sowing seeds, or from taking stem cuttings and truncheons. Take cuttings in spring or summer when the plant is in active growth.
Always remember to wear appropriate long-sleeved clothing, gloves, safety goggles and long trousers when handling Euphorbias, to avoid getting the toxic sap on your skin.
Stem cuttings will root quite quickly and are the easiest to produce. Take a look below for a quick “How-To” guide:
- First get prepared: you’ll need small pots, well-draining compost mix, a clean pair of snips, and a disposable container half-filled with water
- Once you have put your goggles, gloves and long clothing on, take some 6 – 12-inch stem cuttings
- Dip the base of each cutting in the water, rinsing away the bleeding white sap as you go
- Lay the cuttings on some newspaper in a shaded spot for a few days to dry out and heal
- Fill your small pots with the well-draining compost, lightly water and use a dibber or pencil to make about a two-inch deep hole in each pot
- Wearing gloves, place each cutting into the two-inch dibber holes, firming the soil around each one
- Place in a semi-shaded spot at a temperature of 75 degrees F, watering about every 4-5 days once the top half of the soil has dried out
- Leave your cuttings to root for around a month—you’ll know they have rooted when there is some resistance when you gently tug at the cutting tip
The striking colours of this Euphorbia make it the perfect container plant. Whether planted alone or in a group, it has great winter interest and works very well with many other succulents which thrive in similar soil types.
Overall, the Euphorbia tirucalli is an eclectic succulent with an unusual growing form and wonderful winter interest. A great plant for both the “newbie” and the more experienced succulent grower.