Pencil Cactus Care: How To Grow Euphorbia Tirucalli

I love Pencil Cactus and have grown one for many years. This is an easy plant to care for in the home and the garden. There are two key components of Pencil Cactus Care to keep it happy, healthy, and alive.

I’ve had my Pencil Cactus for a very long time now. It’s not the original plant, but a cutting I took in San Francisco, and it traveled with me when I moved to Santa Barbara. I brought a cutting of that plant when I moved to Tucson, so the lineage continues!

I first laid eyes on this plant when I was installing the Macy’s Spring Flower in the late 80’s, and it was part of one of the window displays. This was back before succulents became all the rage as they have been in the past fifteen years or so.  

The show was full of rhododendrons, azaleas, hydrangeas, and the like. So, the Pencil Cactus turned my head. I ended up buying it when the show was taken down.

I’ve grown it as a houseplant and in the garden. Here’s what I’ve learned about this beautiful succulent.

Botanical name:  Euphorbia tirucalli  Common name: Pencil Cactus, Pencil Tree, Milk Tree, Pencil Plants, Indian Tree Spurge, Milk Bush

A popular variety of this plant is called “Sticks On Fire.” It doesn’t grow as large and has vibrant reddish/golden stems.

Note: This post was published on 11/4/2015. It was updated on 11/8/2023 with more info & new images.

Pencil Cactus Care Indoors

Pencil cactus grows indoors in a white pot next to a window.
This plant is from a few cuttings planted two years ago. When you scroll down to the “Repotting” section, you can see a picture of me planting it.


Pencil Cactus grow bigger when living outdoors. Mine in the photo above is two years old, grows in a 10″ pot, and is 6′ tall x 2.5′ wide. I keep it pruned on the narrow side at the base so we can open the door!

Most Pencil Cacti I’ve seen sold in the indoor trade are in 6″, 8″, and 10″ grow pots. Their size ranges from 1′ to 5′.

The tallest I’ve seen one growing indoors is 9′. Mine will eventually get taller than that because it receives plenty of bright, natural light and has plenty of room to grow upwards, as the ceiling in my entryway is 13′.

Light Requirements

Pencil Cactus requires high light when growing indoors. It’ll need plenty of bright light to thrive. Place your Pencil Cactus in or near a west or south-facing window that receives at least 4-6 hours of direct sunlight daily. Just be sure it isn’t touching hot glass.

Mine grows in front of a tall, narrow south-facing window with another window at the top (not seen in the photo) and a picture window across the room, so it receives plenty of natural light all day.

You can tell if your Pencil Cactus is in light conditions that are too low if it starts to stretch out, lean towards the light source, or if the growth is looking weaker. If that happens, relocate it to a brighter area.

Rotate it every few months if it’s not getting enough light from all sides. This is especially true in the cooler months when the light will be less intense in your home. 

Up close of the dense growth on a pencil cactus with small leaves.
The dense growth of a mature Pencil Cactus. If you look closely, you can see tiny leaves on the stems & at the end of the stems. On my Pencil Cacti, the leaves are present in spring, summer, &/or fall.

Water Requirements

Pencil Cactus is a succulent, so it’ll need less frequent watering than your tropical house plants.

In a nutshell, let the soil go dry before watering again. I water mine in a 10″ pot every two weeks in summer and every three to four weeks in winter.

Yours might need watering less or more often. Many variables come into play, like the pot size, the type of soil it’s planted in, its growing location, and your home’s environment. The more light and warmth, the more often yours will need watering.

If unsure, consider getting a moisture meter to monitor the soil dryness/wetness.

This post on watering succulents indoors will give you more information.


If your home is comfortable for you, it’ll be comfortable for your Pencil Cactus. It can tolerate our home temperatures and lack of humidity just fine.

To give you an idea of the extremes this plant can handle, mine growing outdoors in Tucson, AZ endures the 100F+ temps in summer and temperatures down to 28F in the winter.

Nell Foster outdoor standing next to a large pencil cactus growing on back patio.
My Pencil Cactus in Tucson just before it got repotted. It’s much happier now in a bigger pot, so it can stand up on its own & not have to lean on the wall.

Pencil Cactus Care Outdoors


Pencil Cactus plants are native to Africa and, in their native environment, can grow to 30′, which is why they’re also called Pencil Tree. 

As they mature, their branches flop and bend downwards as they grow. These plants can reach impressive heights in regions with a suitable climate; the tallest one I’ve seen was 15′ in the LA area.

Mine, growing in a pot in Santa Barbara, was around 6′ tall. You can see it pictured below. My newly repotted Pencil Cactus in Tucson is 8′ tall by 6′ wide.

Light Requirements

In Santa Barbara, zone 10b, my Pencil Cactus thrived in the late morning and afternoon sun. The mornings and late afternoons in summer were often foggy and cool, so full sun was fine.

In Tucson, zone 9a, where the summers are hot and intensely sunny, mine does best in bright shade. It receives morning sun for about an hour or two.

Pencil cactus grows outdoors and terra-cotta pot with other succulents against wooden fence.
My Pencil Cactus is growing in my backyard in Santa Barbara.  Mature plants are heavy as they grow larger, & need a substantial base.

Water Requirements

With its succulent characteristics, the Pencil Cactus thrives in conditions with minimal water.

During the summer, when it’s growing season, infrequent but deep waterings are ideal. It ensures that the roots receive moisture, and the soil can dry out between watering sessions, preventing the risk of overwatering, which can be detrimental to these plants.

Mine grew in a large terra cotta pot measuring 28″ x 28″ in Santa Barbara. During the summer, I watered it every month or so, providing two big watering cans full at a time.

In Tucson, I was watering mine in an 18″ pot every 7-10 days in summer. It was just repotted into a 29″ x 29″ pot (badly needed!), so I imagine it’ll be every two weeks in summer.

The smaller the pot, the more often it’ll need watering.

I back off on the watering frequency in the winter months. How often depends on the temperatures and the rainfall.

If you want more details on this, check out how often should you water succulents.

General Pencil Cactus Care

Pencil Cactus Soil

Like other succulent plants, a Pencil Cactus must grow in a mix with good drainage and aeration. Using chunky or gritty soil specially formulated for cactus and succulents is best.

For years now, I’ve been making my succulent soil. You can find the DIY Succulent Soil Recipe here. My outdoor and indoor succulents grow well in this fast-draining mixture of coco chips, coir, and pumice.

If you don’t want to make your own, there are plenty of online sources to buy the mix. I’ve used Dr. Earth, EB Stone, Bonsai Jack, and Tanks’. Other popular choices are Superfly BonsaiCactus Cult, and Hoffman’s.

If you’re growing Pencil Cactus in a container, make sure that the pot has adequate drainage holes to allow excess water to escape. The build-up of too much water can quickly cause root rot; the water needs to drain out of the container it’s growing in. 

If it’s in the ground, that might mean adding some loam to your soil or other material to add the drainage. You can check with your local landscape supply company to see what they provide.

Indoors: I always use straight succulent and cactus mix with some amendments (compost and worm compost) mixed in.

Outdoors: I used 3/4 succulent & cactus mix and 1/4 potting soil with amendments added in coastal Santa Barbara.

I recently used 1/2 succulent & cactus mix with 1/2 potting soil and added amendments in hot, dry Tucson, where I want the soil to hold more moisture.

The potting soils I use on the regular are Happy Frog and Ocean Forest.

Nell foster repots a pencil cactus cutting indoors.
This is the Pencil Cactus growing next to the door (seen in the photo up top) when I planted it from a few cuttings. You can see how much it’s grown in two years!


The best time to repot a Pencil Cactus is during the growing season. That’s spring and summer into early fall. 

Pencil Cactus, when small, don’t have an extensive root system. They’re happy to stay in the same pot for a while, but at some point, they’ll need to be transplanted into a new pot. 

I repot mine when the plant is out of scale with the pot. Pencil Cactus get heavy as they grow and need a bigger base to support that. On average, I repot mine every four to seven years.

They get much harder to repot as they get larger because of the weight issue. When my large Pencil Cactus was repotted a month ago, I had three men doing the job. The plant was so heavy I couldn’t move it, let alone lift it into a 29″ pot!

Try not to break branches or stems when repotting this plant. Read the section on “Pencil Cactus Sap/Toxicity” below.

Here’s a general guide to repotting succulents, which you’ll find helpful.

Pencil Cactus Fertilizer

A Pencil Cactus isn’t fussy in this department. When planting, I feed mine with a worm compost/compost blend and top dress every two or three years in spring.

During the growing season is the best time to feed your Pencil Cactus. We have a long growing season here in Tucson from mid-February through October. I fertilize with  Maxsea or Sea GrowGrow Big, and Liquid Kelp five times during the growing season. I alternate using fertilizers and don’t mix them.

Whatever indoor plant food you choose, don’t over-fertilize because salts build up and can burn the plant’s roots. This will show up as brown spots on the stems.

Pencil Cactus Pruning

Spring and summer are the best times to prune a Pencil Cactus. Into early fall is fine also if you’re in a more temperate climate.

These plants grow fast when the conditions are to their liking. You might have to prune yours at some point to control the size, to shape it, or to propagate.

I haven’t pruned my large one growing outdoors lately because it has plenty of space to grow. I prune mine indoors twice a year to control the width.

If your plant is in a pot, you don’t want to prune too much off the base and leave most of the growth at the top. They get top-heavy, and your plant could take a tumble.

Learn more about Pencil Cactus pruning here!

Warning: Be very careful when pruning this plant. Read the section on “Pencil Cactus Sap/Toxicity” below.

Pencil cactus cuttings on the ground outdoors with tape on the ends.
I’ve dedicated a section to pencil cactus sap. Please read it before pruning, repotting, or moving this plant. If a branch or stem is broken or cut, a white sap will drip out. That’s why I have paper towels covering the cut end of each stem.

Pencil Cactus Sap / Pencil Cactus Toxicity

Some say the sap of this plant is overrated in regards to toxicity; others say it’s very toxic. I’ve been growing this plant for over thirty years and have had no issues. I wear gloves when pruning it and am very careful not to get it near my face, especially the eyes or mouth.

I have once or twice gotten a small amount of sap on my arm, which hasn’t irritated me. One of my readers shared that it was highly irritating to him, especially when exposed to the sun. Do some research, and come to your own conclusion.

These plants are considered to be toxic to humans and pets. I get my information on this subject from the ASPCA

My cats pay no attention to my Pencil Cactus, but because of the sap, keep your eye on your pets around this plant.

When I’m pruning, especially indoors, I cover the cut ends on the stem and the plant to keep it from dripping onto the floors, furniture, or my clothes. It can leave black stains.


Pencil Cactus plants are tough cookies! Mine, or any I’ve seen, have had no pest issues.

Like most succulents, mealybugs are the number one pest. Also, keep your eyes open for aphids and spider mites, as they could be an issue.

For most pest infestations, you can control them with neem oil or insecticidal soap. The latter is what I’ve been using for two years now and has been effective.

Pencil Cactus Care Video Guide

Large Pencil Cactus Repotting Video Guide

Conclusion:  Pencil Cacti are easy to grow if you give them two things: bright sunlight and water when the soil is dry.

These wacky yet wonderful plants are great for people who travel or tend to forget (not intentionally, I’m sure; we know how that goes) about their houseplants.

The far-out and fabulous-looking Pencil Cactus doesn’t like to be fussed over in the garden or your home!

Happy gardening,

Signed by Nell Foster

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Pencil cactus growing outside in large pot text rates pencil cactus care indoors and outdoors

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  1. Hi Nell
    Great video really informative ?
    I live in the north east uk (Cleveland) I’ve committed the sin of falling in love and buying a plant without looking it up or researching anything about it …. it looks so different to any other plants I’ve seen and has character.
    After watching your really intuitive video I am assuming I have inadvertently obtained pencil cactus / succulent. I noticed during transportation It did exude a white sap if cut etc. It’s a pity, as I’m not sure how to send you a picture of this rather charming plant I took on my iPhone yesterday. ..
    The plant I purchased last was in the houseplants section in my local garden centre. I assumed it will be one of those “ tender” plants who are unable to withstand the -10 to even -17 (if it’s really grim) winters we can get here and will require tlc.
    In your video you mention it needs light and to water sparingly which is fine, however you say the pencil cactus can get really tall … I suppose my question is can I keep it small ( space is an issue and I can’t put it outside as the ground is still frosty) without making it look as though it’s had a bad haircut if so, how short can I go?
    I really love the uniqueness of this plant and I don’t want to make it suffer as it was quite expensive at £40.
    I’m sure I can’t be the only person in the world to have this I have bought a plant without researching it. ?
    I appreciate any advice help .
    Hands across the sea

  2. Hi Addy – It’s always good to do a bit of research! Give this plant as much light as you can indoors; & don’t over water it. They “mush out” fast. It does get very tall but won’t grow as nearly as much indoors as it will outdoors in warm weather. As to the pruning, mine here in Arizona has grown to 9′ tall. The roof on my covered patio is a bout 12′ so I’ll be cutting the plant back before it touches. I could easily cut it back to 3′ tall if I wanted. You should be able to tell where to cut it back so it looks good. And be careful when pruning – here’s another post for you: Nell

  3. I bought a pencil plant in Aldi supermarket back in October and it is growing well on a table inside by the front door . However it is already about two feet high. I live in Scotland and have an unheated greenhouse so how should I look after it? After reading your article I have reduced the watering and I am going to repot it when I can get a suitable compost. Any advice will be welcome.

  4. Hi Janet – Pencil Cactus are cold hardy to around 25F. Back off on the watering in winter. You can transplant it in spring or summer using a very well draining mix preferably a succulent & cactus mix. Hope that helps, Nell

  5. Hey! How to you get the main stem or trunk to thicken to looks maybe more tree like? I’ve seen photos where the main truck looked really thick!

  6. Hi Logan – Mine have always grown a thick trunk over time. The 2 cuttings which I brought from Santa Barbara to Tucson are now almost 9′ tall. I’ll have to cut them down a bit in fall & that will also thicken the trunk. Nell

  7. What’s the other plant you have in the terra cotta pot with the pencil cactus?

  8. Hi Nell!

    I live in Denver, Colorado, and was gifted a stunning Euph Tiruncalli which is about 6 ft tall, and 7 years old! Very heavy, with only one thick trunk. In her previous life, “Eunice” was inside with north-facing window exposure. Colorado is a very sun-intense state. I got her in June, and she went straight to my full-sun (6-8 hrs) yard and EXPLODED with growth! Technically, I way overwatered her, but instead of croaking, she rewarded me with many new branches and stems! But it is Colorado, so she came in for the winter, to a west-facing window, but not too much intense sun. I watered her last 6 weeks ago, but I’m noticing tiny dry brown bits that break off if I tug, sometimes in the middle of one stem, generally at the ends, or midway (not trunk or tip). So I just soaked her, but I’m unsure what’s going on. Can you help?

  9. Hi Shelly – Mine does that occasionally because it grows so densely & so vigorously. It can happen due to watering or perhaps in your case, explosive growth. Nell

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