Sumo Gardener

Pencil Cactus – How to Grow and Care Guide

I’ve always had an affinity for more peculiar houseplants and the pencil cactus is certainly one of them. It is now a very popular ornamental houseplant cultivated by beginners and experts alike thanks to its very low maintenance demands and its uniquely wiry, green succulent foliage. 

It can be grown as a shrub or a small tree so it’s able to offer a few applications both indoors and outdoors. Today I will be looking into how to grow and care for this spindly specimen so you can have all the information you need to successfully cultivate one of your own


Euphorbia tirucalli commonly known as Pencil cactus





Common Names:

Pencil cactus, Indian tree spurge, pencil tree, milk bush, fire stick


Indoor or outdoor


Shrub, tree

Growth Outdoors:

20 to 30 ft. tall, 6 to 10 ft. wide

Growth Indoors:

Up to 6 ft. tall, 1 to 3 ft. wide

Sun Requirements:

Full sun

Foliage Color:


Flower Color:

Yellow (insignificant)


Spring to summer

Hardiness Zones:

11 to 12 (USDA)

Maintenance Level:

Very low

Poisonous for Pets:

Milky sap is highly toxic to pets and people

Getting to Know the Pencil Cactus

Pencil cactus also known as fire stick cactus

Featuring clusters of pencil-thick, smooth and green succulent branches atop cylindrical and fleshy stems, the pencil cactus does also produce tiny oval-shaped leaves and small yellow flowers in spring to summer, both of which will likely fall off early. 

This is why the plant is predominantly grown for its lush thick branches that can quickly add a playfully quirky presence to any room or outdoor setting.

With the ability to handle a lot of neglect, this plant is the perfect pick for travellers or those who may not have the time to tend to a more temperamental plant. 

Botanically labelled Euphorbia tirucalli, the pencil cactus has many common names including the Indian tree spurge, pencil tree, milk bush and fire stick, the latter of which refers to the plant's vibrant pinkish-red new growth.

The pencil cactus forms a part of the Euphorbiaceae family and it is native to many tropical regions in Africa and Asia including but not limited to South and East Africa, India, Vietnam and even Brazil. 

It thrives in semi-arid tropical climates naturally and will grow well cultivated in homes in USDA Hardiness Zones 11 to 12. 

Pencil Tree Growth Habit

There are varying reports on its growth rate but the pencil cactus will usually grow to around 6 feet tall and 1 to 3 feet wide indoors and 20 to 30 feet tall and 6 to 10 feet wide outdoors. 

This is why most choose to grow this plant in containers indoors as it is significantly easier to manage in those environments.

Fire Stick Cactus Safety Precautions 

It is important to note that this plant produces a highly poisonous latex sap that can cause temporary blindness if in contact with the eyes and if consumed, it can cause severe inflammatory and intestinal reactions in dogs, cats and people.  

Always handle this plant with care and wear protective gear for your eyes, hands and sometimes clothing as the sap also stains fabrics. If grown indoors, be sure to place the plant in a safe location if you have any curious pets or children. 

Always clean your tools with rubbing alcohol after handling your pencil tree.

How to Grow Pencil Cactus

Euphorbia tirucalli is best planted during its active growing season from spring to early summer. Once established, this plant shows impressive resilience and will only require basic growing conditions in the right zones. 

How to Grow Pencil Cactus

Positioning Pencil Tree for Ideal Exposure

Thriving in sunny locations, this plant needs at least 6 hours of full sun on most days. It can tolerate more shaded afternoon conditions as well. If grown indoors, place it by your brightest window.

Best Soil for Successful Growth

Milk bush will perform at its best in dry, sandy, well-draining soil with a neutral to acidic pH level. The soil shouldn’t be too rich in nutrients.

For container-grown plants, use a high-quality succulent or cactus potting mix that doesn’t retain moisture. Can’t check your soil’s pH level? (Check out this soil tester.)

Temperature and Humidity

This plant needs warm temperatures of between 65 and 75°F most days. Temperatures ideally shouldn’t drop below 50°F too frequently. Indoors, be sure to shelter your plant from cold drafts including those from air conditioning units. 

Pencil cactus enjoys dry, low-humidity environments where the relative humidity is below 40 percent. If your humidity is a little too high, try to ensure that your soil doesn’t retain any unwanted moisture.

How to Propagate Pencil Cactus 

Pencil cactus plants are readily propagated from cuttings done during late spring to early summer. Again, protective clothing is recommended for this process. 

If you’re not too interested in the propagation process, young healthy nursery plants should be available online or at your local garden centres and nurseries. 

Propagating Pencil Cactus

Propagating Pencil Cactus from Branch Cuttings

  • Using a quality, sharpened and sterilized pair of pruning shears, take a healthy cutting from a mature green branch that is around 6 inches long. (See our reviews on highly rated pruning shears for reference).
  • Immediately dip the cutting into fresh water to stop the sap from flowing. This will help to make the process a little safer moving forward.
  • Place the cutting in a dry but sheltered location and leave it for about a week to callous over the cut end. 
  • Once calloused, you can prepare a well-draining container filled with quality, moist cactus or succulent potting mix then pot the cutting into the mix. 
  • Place the newly planted cutting in a sunny location with lots of bright, indirect or ambient light. 
  • Water lightly after planting then allow the soil to dry out before watering again.

Caring for Pencil Cactus

Thanks to how low-maintenance this plant truly is, care is usually kept to a minimum in the right conditions, especially once pencil cactus is established. 

Here are some helpful Pencil cactus care tips that will keep your plant happy and healthy.

Caring for Pencil Cactus

Establish a Good Watering Routine

The plant will require water only a couple of times per month during the warmer parts of the year. In the cooler months, it will require even less. 

On average, water your plant every 2 to 3 weeks in summer and about monthly from fall to winter. Always allow the soil to dry out completely between waterings. 

This plant is very tolerant to drought so overwatering should be avoided. 

Pruning Pencil Tree

Pruning won’t be required too much but prune off dead stems and branches as needed in early spring to encourage healthy new growth and to keep your desired shape and size. 

Prune at the base of stems and branches but don’t take too much from the bottom as these plants can become quite top-heavy. Be sure not to compost cut-off pieces due to toxicity. 

Clean your pruning shears with rubbing alcohol afterwards.

Fertilizing Fire Stick Cactus

This plant is not a heavy feeder and will only require annual fertilizing in spring with a balanced liquid houseplant fertilizer.

Potting and Repotting Requirements

Container-grown plants will need to be repotted once they outgrow their current containers or pots. Repotting should be done in spring every 2 to 3 years. 

Be sure to use a well-draining, unglazed clay container to ensure excess moisture is evaporated through the porous walls. Repot when the roots have filled the container and move one size up each time. 

Cut away any dead roots and remove as much old soil as possible when moving your plant to its new home.

Rotating Regularly

Be sure to regularly rotate your plant to ensure equal growth.

Overwintering Fire Stick Cactus

For container-grown plants outdoors, be sure to bring them inside during the harsher periods of winter to ensure they survive. You can place them back outdoors once temperatures don’t fall below 50°F overnight.

Euphorbia Tirucalli Common Pests and Diseases

There are no notable pest or disease issues for these hardy houseplants other than possible infestations from spider mites and aphids on rare occasions.

These pesky invaders can be treated with neem oil or a horticultural soap or spray. Overwatering and excess soil moisture can cause root rot so be sure to always allow the soil to dry out completely before watering again.

Pencil Cactus Frequently Asked Questions

How to Propagate Pencil Cactus

What happens if you touch a pencil cactus?

The thick latex sap is very toxic to both humans and animals. If the sap makes contact with the skin, it will quickly cause redness, rashes, burning and other skin irritations. 

Avoid getting the sap in your eyes at all costs as it can cause severe irritation and even blindness if left untreated.

How fast does pencil cactus grow?

In good conditions, this plant will usually grow between 2 and 20 inches each season. 

Why is my pencil cactus turning red?

This is a completely normal occurrence. New growth appears as a pinkish-red that will mature over the growing season. In its native habitat, red is the natural color of many of these plants.

Pencil cactus will also turn red if its environment is cold but bright enough outdoors.

Is pencil cactus good for a home?

If situated safely in your home, this plant makes for an excellent houseplant that provides interesting and attractive silhouettes to any room.

Should you be interested in establishing other gorgeous cactus types in your home or garden, be sure to have a look at our helpful guide below:

Perk Up Your Living Spaces with the Persuasive Pencil Cactus

As much as the toxicity can be a slight deterrent, I think this plant deserves its notoriety still thanks to its excellent houseplant characteristics. Perfect for all growers, especially travellers, Euphorbia tirucalli truly defines low maintenance whether indoors or in your garden.

Enjoy exciting new growth and consistently captivating silhouettes with the pencil cactus plant.

About the Author Mabel Vasquez

Mabel has enjoyed a long career as a horticulturist, working in nurseries and greenhouses for many years. Although she loves all plants, Mabel has developed a particular passion over the years for herb gardens and indoor plants. Mabel has since retired from her horticulture career and loves sharing her many years of experience with our audience here at Sumo Gardener.

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