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Pencil Cactus – 21 Questions Answered (Euphorbia Tirucalli)

Pencil Cactus – 21 Questions Answered (Euphorbia Tirucalli)

Despite what many people believe, the Pencil Cactus is not classified as a cactus. It is also known as the firestick plant, naked lady, and milk bush. This plant is actually a small tree or shrub that belongs to the Euphorbiaceae family.

Euphorbia tirucalli, or the pencil cactus as it is commonly known, is native to Africa and is predominantly found in dry areas with black clay soil. With smooth, succulent branches, this shrub can grow up to a height of 22 Feet (7 meters). It has become a popular decorative plant worldwide.

Known as the firestick plant because of the orangey-red color that makes this plant look like it is on fire during the cooler seasons, this family of flowering plants is easy to grow either indoors in pots or outdoors in full sunlight.

They are perfect plants for beginner gardeners as they do not need much attention and will grow well in almost all conditions.

History Of The Pencil Cactus

This succulent shrub or small tree is easy to recognize because of its pencil-thick, green, smooth branches, with small yellow flowers at the ends of the branches and small, oval leaves growing on the branches.

The name pencil cactus is derived from the cylindrical shape of the branches, which are around the thickness of a pencil.

More mature plants have thicker brown branches with smaller green branches at the end, which resemble a firestick.

Although often mistaken as a member of the cacti family, the pencil cactus lacks the sharp spines that are common to most cacti.

Found throughout much of the northeastern, central, and southern parts of Africa, it grows in the wild without much attention in dry, arid areas.

The pencil cactus has been introduced into other tropical regions of the world, such as Brazil, India, Vietnam, and the Philippines, where, because of its size and height when growing wild, it is often used as a hedge.

Because of its beautiful green stem color and short, red, orange, yellow, and green twigs, the pencil cactus is often used as an ornamental plant in gardens and landscaped areas. 

Is The Pencil Cactus Toxic?

The pencil cactus plant is a plant that produces an acidic milky white sap or latex, which is highly toxic to both humans and animals. The sap is released once the stem of the plant is broken, so it should never be ingested or touched with bare skin.

The toxin from the sap can cause severe skin, mouth, and eye irritation in humans. Gastrointestinal problems and blindness has been reported in severe cases.

This plant should never be planted in areas where children are going to play and should be kept away from small children who may try to chew on the plant.

In animals who have ingested the sap, vomiting and mouth irritation occurs, so this plant should be kept away from areas that animals are allowed into.

When working with this plant, always make sure that you are wearing the necessary protective gear such as rubber gloves and goggles to prevent being poisoned by the sap.

What Are The Symptoms Of Pencil Cactus Poisoning?

When the sap touches the skin, it can immediately cause redness, burning, blistering, and a nasty rash in both humans and animals. If any sap gets into the eyes, they will swell and become very painful.   

If the sap is ingested, it can cause vomiting or diarrhea or, if ingested in high amounts, can be fatal.

Humans or animals that are allergic to the toxin could suffer an anaphylactic shock. If poisoning is suspected, take the patient to your nearest medical facility immediately. 

What Is The Pencil Cactus Used For?

The pencil cactus plant is a species of hydrocarbon plant, meaning it naturally produces a substance similar to petroleum. The sap of this plant has been tested as a fuel source and has been used in the production of rubber.

In some countries, the pencil cactus has been used in traditional medicinal healing to treat the symptoms of asthma, coughing, earache, and rheumatism. However, due to its toxicity, you should never ingest any part of a pencil cactus or expose your skin or eyes to its sap.

Perhaps the most popular use of the pencil cactus is as a decorative ornamental plant.

How To Care For A Pencil Cactus Plant

Pencil cacti, like other succulent plants, fare well in high temperatures and with little rainfall. This means they don’t need much attention, only an occasional watering when the soil becomes dry.

This makes the pencil cactus a great option for people who lack a “green thumb” or tend to forget to water their plants. Pencil cacti can withstand a fair amount of neglect and keep on living. 

Just make sure to avoid over-watering your plant. Pencil cacti are accustomed to dry soil, they actually prefer that the soil dries out in between waterings.

A good rule of thumb is to water your pencil cactus once every ten days during warm months, and as little as once a month during the winter. 

Can You Grow Pencil Cactus Indoors? 

A pencil cactus plant will thrive indoors if the conditions are right. They are not a fussy plant and don’t need too much attention. If planted correctly, they will continue to grow without much care.

However, pencil cacti don’t do well in low light. Make sure your plants get plants of light next to a nice sunny window.

In cooler climates, the pencil cactus is a common indoor ornamental plant because of its hardiness and beauty.

What Are Best Containers For Growing A Pencil Cactus Indoors? 

For your pencil cactus plant to grow well indoors, you need to use the right container. 

The best pots for succulents have excellent drainage and are large enough to accommodate the growth of the plant. A pencil cactus can grow long roots, so using a deep pot is ideal. By giving the roots plenty of room to grow, you help the plant to grow large, stable, and healthy. 

Ceramic or glazed terracotta pots are the ideal choice for succulents as they are porous and prevent waterlogging. The only downside to these pots is that they can become very heavy when filled with soil and plants, so make sure you have the pot in its final position before adding the soil and plants.

If you are planning on moving the potted plants, try using plastic or resin containers as they are lighter and will be easier to move. Make sure they have proper drainage holes before filling them

The downside to using plastic pots is that they are poor insulators—in extreme temperatures, plastic pots do little to protect the roots of your plant. During hot summer months, some growers complain that the roots of their plants get cooked as the water is baked off rapidly.

You can fix this by watering more frequently, painting the pots white, or by wrapping them in something reflective like aluminum foil. 

Do some research on the internet for ideas on good pots, or visit your nearest garden center.

Can You Grow A Pencil Cactus Outdoors?

The pencil cactus will thrive outdoors in areas with direct sunlight. Even though it can tolerate some afternoon shade, it thrives with four to six hours of sunlight per day, so grow this plant in the sunniest spot in your garden.

How Much Light Does A Pencil Cactus Need?

When growing the plant indoors, it still needs plenty of light. For the best lighting, place your cactus near a south or west-facing window, or any window with bright light. 

The pencil cactus plants will not thrive in areas with low light, but they will continue to grow as long as they are watered regularly and kept in a temperature-controlled environment.

Be sure to rotate your pots at least once a month so that the plant gets sunlight on all sides.

What Is The Ideal Temperature For A Pencil Cactus Plant?

The ideal temperature range for a pencil cactus is between 50 – 75 degrees Fahrenheit (10 – 24 degrees Celsius).

They are not very cold-hardy plants and don’t do well in temperatures below 30 degrees Fahrenheit (-1 degrees Celsius).

Being a semi-arid tropical plant, pencil cacti can survive in temperatures as high as 100 degrees Fahrenheit (37 degrees Celsius).

During the winter, you can protect your outdoor plants from frost by covering them in frost cloth or plastic, or by moving them indoors or into a greenhouse. 

How Much Water Does A Pencil Cactus Need?

Only water a pencil cactus once the soil dries out. During a hot, dry summer, you could water your plants every ten days, but in the winter, you can reduce watering to once a month. 

To avoid overwatering the plant, allow the soil to dry out completely in between waterings. If the plant receives too much water, its roots can rot, causing the plant to die if not treated in time. If the soil still feels moist to the touch, it’s too soon for another watering.

How To Water A Pencil Cactus

With indoor plants, make sure that you wait for the soil to dry out completely. How much you water the plant depends on whether the pot it’s in has drainage holes or not. Moisten the soil without over-saturating it. 

During rainy months, you likely won’t have to water your pencil cactus at all. Again, just check the moisture level of the soil with your fingertips, if it’s still moist, don’t water it. If the plants become brown and wrinkly, you need to water the plants and thoroughly soak the ground.

What Are The Soil Requirements For A Pencil Cactus?

The pencil cactus needs soil with excellent drainage to grow well, either as an indoor plant or outdoors in your garden.

As they prefer dry, sandy soil, they are perfect for planting and adding color to a rock garden or any other hard-to-grow areas in your garden.  Add perlite to the area to improve the drainage for your plants.

A great potting mix for pencil cacti is two parts cactus mix and one part perlite. These plants don’t need much fertilizer, you can amend the soil with a standard all-purpose fertilizer just once a year. 

Can I Grow A Pencil Cactus From Seed?

You can grow a pencil cactus from seed, but as the seeds are tiny, most gardeners opt to buy already grown plants from a garden center. If you would like to try and grow the plant from seed, contact your nearest garden center for advice on what to do.

How To Prune A Pencil Cactus

Pruning may be required if the pencil cactus grows out of the space that you have for it or if the plant generally grows too big outdoors.

What Do I Need To Prune A Pencil Cactus?

Pruning a pencil cactus is not always necessary, but if you have to cut it back or prune it eventually, it’s best to have the correct equipment for the job.

  • A pair of long-sleeved, thick rubber gloves for protection from the latex sap.
  • If pruning large plants, a pair of safety goggles should be worn to protect your eyes.
  • Covered shoes, long pants, and long sleeves are a good idea to protect your skin from rashes because of the latex sap.
  • A pair of pruner blades.
  • A bleach solution to clean the blades after cutting through the sap made of one part bleach mixed with nine parts water.
  • A spray bottle containing clean water.

How Do I Prune A Pencil Cactus?

Pruning a pencil cactus plant can be done at any time during the year. Some gardeners follow an annual schedule of pruning and tidying up their plants before or after certain seasons during the year. Schedule these necessary jobs according to what suits you best.

First, cut back any broken or dead stems from the plant which you are working on. Cut the branch outside the joint without leaving a stub.

Keep trimming away the branches that are too large or are not healthy on the plant until they fit the space you have for it, whether indoors or outdoors. Regular pruning of the old branches stimulates new growth, and you can shape the plant to how you would like it to look.

Once you have cut off a branch, spray the cut on the plant with clean, fresh water to stop the sap from oozing out. 

After cutting and shaping the plant to your requirements, wash down the pruners in the bleach solution to remove all the toxins from the sap.

If the plant is growing in a pot or container, move it into a well-lit area and make sure it gets enough water to help it recover. 

If the plant is outdoors, keep the soil damp but do not overwater. Add some extra soil and nutrients to the bed for the plant to recover and to encourage new growth.

How To Propagate A Pencil Cactus From Cuttings

Growing a pencil cactus from cuttings is relatively easy, but care must be taken to avoid the sap when harvesting from the parent plant and replanting the cuttings.

What Do I Need To Take Cuttings From A Pencil Cactus Plant?

To care for the cuttings and to prevent root rot and disease, light and water are crucial, along with:

    • Small pots, deep enough to support new root growth
    • Potting soil or a soilless medium such as peat moss or vermiculite
  • A spray bottle with clean water
    • A sharp pair of scissors, knife, or razor blade to prevent damage to the parent plant
    • Garden gloves for protection from the sap
  • A healthy plant

How Do I Take Cuttings From A Pencil Cactus Plant?

Taking a cutting from the pencil cactus plant largely depends on which season you plan to grow the new plants. The best specimen for a cutting should ideally be several inches long with numerous growth nodes and full foliage.

  • A softwood cutting, or this season’s new growth, is ideal. The cutting will root well as it hasn’t had time to harden on the parent plant.
  • Semi-softwood cuttings are taken in summer just before the new growth is mature.
  • Hardwood cuttings are taken from a mature plant.

How To Root Cuttings From A Pencil Cactus Plant

Always remember to wear gloves before taking any cuttings from a pencil cactus plant to protect you from the latex sap’s harmful effects.

Once you have decided on the specimen to be harvested for a cutting, use the sharp blade to cut the parent plant’s specimen as per the above instructions.

The cutting needs to dry out and callus before it can be re-planted, so leave it outdoors in the sun for a few days until it is dry.

Callus on Pencil Cactus Cutting

Fill the pots with the growing medium and spray water over the medium until damp and not soaking wet.

Plant the cutting with the cut end buried into the damp growing medium in the pot. Bury the end of the cutting at least 1 – 1 ½ inches (2.5 – 3.8 cm) into the medium.

Pencil Cactus Cuttings in Pot

I use a homemade cactus soil mix that’s (3) parts sand, (3) parts regular potting soil, and (2) parts perlite.

Place a small plastic bag over the pot’s cutting and place it in an area with indirect sunlight or into a growing tent. The ideal temperature for new growth should be between 55 – 75 degrees Fahrenheit (13 – 24 degrees Celsius).

To encourage airflow and to spray freshwater onto the cutting, open the bag regularly. Make sure that the growing medium is kept damp.

Check the cutting for root growth regularly and re-pot when the root system is established. The root system could take up to a month to develop and grow.

The new plant can be re-potted into a bigger indoor pot or directly into your garden bed. Watch the new plant carefully and keep re-potting once the plant has outgrown its current space.

Will A Pencil Cactus Cutting Root In Water?

A pencil cactus, although a hardy plant that is used to surviving in dry environments, will root perfectly in the water. A good reason to root your pencil cactus in water is to propagate many new plants without buying new plants from the store. By propagating your own plants, you can have as many as you can grow without spending anything.

The success of rooting your cutting in water would depend on the plant itself and the environment that it is in. Sometimes the timing is not right for the cutting to root in water, but generally, you will have success with rooting a pencil cactus plant in water. 

How Do I Root A Pencil Cactus Cutting In Water?

Once you have harvested the specimen from the parent plant, leave the cutting outside for a few days to dry in the sunlight. The cut part of the specimen needs to be calloused over before placing in the water to root. This could take up to one week.

Fill a glass jug or vase with clean fresh water. Measure the depth of the water by how long the cutting is. The root should be in the water, but not any of the leaves on the cutting.

Place the cutting into the water with the cut end of the stem just inside the water.

Place the glass jug or vase containing the cutting into a sunny area and wait for the plant to root. This could take up to one month.

Check the water regularly. You may need to replace the water often to prevent fungus and bacteria from forming in the water and infecting the plant.

After the roots have grown in the water, transplant the new plant to an indoor pot or an area prepared outside in your garden. Make sure that the soil is moist and that you are using the correct potting soil if planting it into a pot.

How To Transplant A Pencil Cactus Plant

Your indoor potted plant may at some stage become too big for the pot that it is in. It can easily be transferred to a different, bigger pot without causing too much trauma to the plant.

Be careful not to move the plant from its existing home until the soil that it is currently in is completely dry.

First, choose a new suitable pot with ample drainage holes in the bottom. Next, gently lift the plant from the existing pot and knock off the excess soil. Trim the dead and shriveled roots from the plant.

Place the plant into its new pot and cover it with a fresh potting mix. Wait for about one week before watering to give the plant a chance to recover.

Common Problems When A Growing Pencil Cactus

As we know, the pencil cactus is a fairly hardy, healthy plant. However, pencil cacti are susceptible to some pests and diseases. Sometimes the plant requires extra watering, more sunlight, or extra soil nutrients to bring it back to health.

Let’s discuss a few of the common problems associated with the pencil cactus and how to treat them.

Why Is My Pencil Cactus Turning Red?

During the colder months of the year, the pencil cactus will turn orange and red, giving it the nickname, Firestick.

The pencil cactus is often planted alongside other succulents as their vibrant colors bring joy to every garden! This is not a disease and does not mean that the plant is unhealthy. It will change back when the weather is warmer.

Why Is My Pencil Cactus Turning Yellow?

There are a few reasons why this could be happening to your plant.

  • Not enough light
  • Incorrect soil type
  • Over or under-watering
  • The air temperature is either too cold or too hot

Why Is My Pencil Cactus Plant Turning Brown?

If the leaves and stems on the pencil cactus plant are turning brown, it could be getting too much light and heat and not enough water. The plant requires around six hours of sunlight per day, but if the sunlight is extreme, it could burn the leaves and stems, turning them brown.

Provide some shade cover for the plant during the hottest time of the day, water if required, and it should recover.

Which Pests And Disease Will Attack The Pencil Cactus Plant?

Although most pests stay away from toxic plants, your indoor pencil cactus plant can be attacked by common household pests such as mealybugs, spider mites, and aphids 

If the plant has been over-watered and root rot has occurred, mealybugs or spider mites could attack the plant. The signs to look for are fuzzy white patches on the twigs or webbing on the succulent.

The only way to eliminate pests is to treat them with an insecticide or neem oil or cut back the infected branches.

To treat root rot, allow the soil to dry out and don’t water again until the soil is dry.

Why Is My Pencil Cactus Dying?

Usually, a pencil cactus plant will only die if it is continually over-watered. Signs of too much moisture are drooping growth, discolored foliage, and mushy stems. It should recover if caught in time by moving the plant to a different pot and allowing it to dry out.

Remember to follow the above instructions in this article on how to water your pencil cactus.

Eventually, the plant will die from natural causes, but it should live to a good age with some care.


The pencil cactus is an ideal plant to keep indoors even if you don’t have the time to tend to it often. It can handle neglect and is a very low-maintenance plant.

By providing your pencil cactus plant with bright light, sandy soil, and occasional watering, it should grow, thrive, and live a long life.

Its vibrant colors and unique foliage are a welcome addition to any garden or home.