The Euphorbia Tirucalli is one of over two thousand splendid and diverse plant life within the Euphorbiaceae family. A wide spread family of stem succulents, which have evolved over time and now have many characteristics of cacti. This clever plant adaptation has enabled this genus to survive in some of the harshest of natural habitats, from the dry, arid landscapes of Southern Africa, Tanzania and Kenya to India, Indonesia, China and Sri Lanka.
Species of the Euphorbiaceae range from huge, towering trees, such as the Euphorbia ingens, to the small and slow-growing Euphorbia bupleurifolia, which in maturity reaches a height of just 8 inches tall. More than two thousand Euphorbia species grow throughout temperate areas of the world, with an estimated more than 200 found in Southern Africa alone.
Regardless of their country of origin, they all have one component in common, this being their toxic latex sap held within their stems and branches – just one of the characteristics used to identify them, promoting their inclusion into the botanical Euphorbiaceae family.
The Euphorbia tirucalli
The Euphorbia tirucalli is my species of interest today, also known as the “Pencil Cactus” or “Sticks of Fire”. Native to the semi-arid and tropical climates of Africa, being most prolific in the North Eastern province, Central and Southern Africa, where this branched and variable succulent readily self-seeds, often reaching heights of up to 30 feet tall. Its useful, though somewhat dense, thicket-like structure is one regularly used as farm barriers and hedging, hence its common name of “Rubber Hedge Euphorbia”. Further uses as cattle feed crops, plus extensive commercial cultivation for the production of fuel, (of similar properties to that of gasoline), has made use of this fascinating plant species natively found growing contentedly in rocky outcrops, grassy hilltops, bushveld and vast regions of open savannah.
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 temperate environment, the Pencil Cactus is quite a common sight in Sri Lanka, where in Tamil it has the common name of Kalli. In less temperate areas of the world we treat the Pencil Cactus as a frost-tender succulent, perfect for greenhouse or conservatory growing all year round and outdoor growing in zones 9 to 12 only.
Many succulent 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, which is far more manageable than a typical native 30-foot specimen!
A Fuel Producing Hydrocarbon Plant
This Euphorbia tirucalli is a hydrocarbon plant. 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 between 10 to 50 barrels of oil per acre could potentially be produced. Unfortunately, Mr. Calvin found he had over-estimated the production levels, his quest was unsuccessful and the idea was later scrapped.
Various parts of this eclectic succulent have been used for many years in traditional medicine. It is reported have many medicinal properties, ranging from a cure for impotence to the antidote for snakebites. I must say I wouldn’t recommend testing these claims myself, but I always find it interesting when a toxic substance is supposedly used to heal people.
History of the Euphorbia Tirucalli
The family and genus name “Euphorbia” were given by the Swedish botanist and author Carl Linnaeus way back in 1753. It was in honour of one of Linnaeus’ great hero’s “Euphorbus”, who was a fine first century physician to King Juba of Mauritania. Euphorbus commonly created traditional medicines using plants within 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.
Growing Form of the Euphorbia Tirucalli
The Euphorbia tirucalli is popular within the house-plant 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.
You can expect a mature height of between 6 to 8 feet high, 1.8 – 2 m, with a relatively similar sized spread. Its form is spineless, upright and branching, with slender stems the diameter of a pencil, hence the common name of “Pencil Cactus”. Branches of this unique-looking succulent are cylindrical and smoothly toothed, only around 8 mm in diameter, and glaucous grey-green in colour. These branches produce small and slender, pendulous branchlets with a rounded crown appearance. New, young growth has a pink hue and very tiny leaves, but both of these characteristics disappear once the plant reaches maturity.
As this succulent has no adult leaves, you may be wondering how photosynthesis takes place?
Due to the wonders of plant adaptation, this Pencil Cactus uses its spineless, succulent green stems to photosynthesise. This natural adaptation means the plant is able to minimise its surface area and in turn, limit excess water losses. This may not be of great value when grown in your home, but in its native high-light habitat this could be fundamental to its wellbeing.
A Chameleon Plant
Towards the end of the summer, you will notice that your Pencil Cactus will start to change from glaucous green to a more yellow and golden tone of colour, this will progress into the winter months turning to ginger and then deep orange to red. A truly stunning transformation, providing brightly coloured branches of unexpected winter interest with a totally uniquely branched and upright habit.
Flowers of the Euphorbia Tirucalli
The form and fiery shades of this super-succulent are what attracts us to the Euphorbia tirucalli, the flowers are rather insipid when compared. However, small clusters of flowers are borne on the crown and inner angles of short branches anytime from September through till December. These attract loads of wildlife, but the bees and butterflies are primarily responsible for its pollination.
Fruits and Seeds
The fruits are produced from November to December time, in the form of pale-green capsules, up to 12 mm in length each with a pink hue and lots of soft light hairs.
The seeds are smooth and dark brown, each around 5 mm 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 to ensure you have a very happy plant.
Planting the Euphorbia tirucalli
Where shall I place my potted Euphorbia tirucalli?
Your Euphorbia will be comfortable 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 are really trying to achieve. Indoors in a sunny spot, or grown outdoors in a conservatory or glass house would suit. Remember these are a frost-tender species and only suitable for outdoor growing (year-round) in limited zones – 9 – 12.
What is the Ideal Growing Temperature?
An ideal minimum temperature of 65 degrees F, or 18 degrees C is needed year-round to keep your Euphorbia tirucalli happy. I always like to keep my houseplants at around 70 degrees F, around 21 degrees C, and these seem to get on just fine.
Which potting soil should I use?
I would recommend using a course, sandy growing medium for this Euphorbia, with a slightly acid 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 the Pencil Cactus does not like to be kept wet ,or like to be sat in any excess water.
Toxic Properties of Euphorbias – what you need to know.
All Euphorbias contain a milky plant sap within their stems and branches. Even if you brush past these plants you are 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 which most often causes an adverse reaction in those who do not wear gloves, or take extra care when handling their plants.
Further complications, such as blindness, skin blisters and even fatality can occur when these 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, I would highly recommend wearing suitable gloves to avoid any potential problems, which could so easily be avoided.
Caring for the Euphorbia tirucalli
How much water will my Euphorbia need?
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.
I would 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 start from late October through until the following March.
When do I feed my Pencil Cactus?
I would recommend using a well-diluted liquid fertilizer on your Pencil Cactus, once every couple of weeks throughout the Spring. A succulent fertilizer would be perfect, but only feed when you have already watered your plant and the soil is wet.
Is any pruning necessary?
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 your plant to expand over time.
How can I propagate from my Pencil Cactus?
You can propagate from your Pencil Cactus by means of sowing seeds, or from taking stem cuttings and truncheons. Cuttings are best taken 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…
How to Take Stem Cuttings from Euphorbia tirucalli
- First get prepared – you will need small pots, a 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 will 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.
Photos courtesy of Pinterest