Pencil Cactus Care Guide: Essential Tips for a Healthy Euphorbia Tirucalli

Last Updated: October 16, 2023

Pencil Cactus

Pencil Cactus

Introduction to the Pencil Cactus Houseplant

Also known by its scientific name Euphorbia tirucalli, the Pencil Cactus, despite its name, is not a true cactus. This plant is a member of the Euphorbia family, which is a large plant family made up of over 7,000 individual species.

The Pencil Cactus, native to Africa, has a distinct growth pattern that sets it apart. Strong, upright stems that resemble chunky pencils or sticks branch out from the base.

This plant is also loved for its resilience as it’s remarkably easy to care for, needs minimal attention, and is highly adaptable to a variety of indoor conditions.

Pencil Cactus Characteristics


The Pencil Cactus gets its name from its distinctive, pencil-like branches. These are slender, cylindrical, and greenish in color, giving the plant an appearance somewhat akin to a bunch of elongated, upright green pencils.


While in its natural habitat, the Pencil Cactus can grow to remarkable heights of up to 30 feet. However, when kept as an indoor plant, it typically reaches a more manageable height of 4 to 6 feet.

Growth Habit:

This plant has a fast growth rate and tends to grow in a bushy, vertical manner. It’s known for its sprawling habit, which can be controlled with regular pruning.


Rarely, the Pencil Cactus may flower indoors, producing inconspicuous blooms. However, this is not a common occurrence and should not be expected in home environments.


A key characteristic of the Pencil Cactus is the milky white latex it produces when cut or broken. This latex is toxic and irritating to skin and eyes, so caution is required when handling the plant.

Light Requirements for Pencil Cactus

Native to regions of Africa, this succulent member of the Euphorbia family thrives best in beight light conditions, mirroring its natural habitat. However, it also displays a surprising level of adaptability, making it an excellent choice for indoor gardening.

Optimal Light Conditions

The Pencil Cactus plant, like all succulents, loved sunlight. It flourishes best when exposed to bright but indirect light. But while it enjoys sunlight, a lot of direct and intense light can cause scorching.

Indoor Lighting for Pencil Cactus

The Pencil Cactus can survive under artificial light. Fluorescent lights, particularly those designed for plants, can be an excellent alternative.

Adapting to Lower Light

The Pencil Cactus can also adapt to lower light conditions. If necessary, it can survive in partial shade or in rooms with less sunlight. However, growth may be slower in these conditions and the vibrant green color may not be as pronounced.

Note: Pencil Cactus, like other Euphorbia species, can become “leggy” or elongated when they don’t receive enough light. If you notice this, consider moving your plant to a brighter location.

Watering Needs of Pencil Cactus

Although it can withstand periods of drought, it still requires a certain level of care when it comes to hydration. Knowing the right watering technique is crucial for the health of your Pencil Cactus.

The first rule of thumb is to always remember that less is more when watering this plant. Excessive watering can lead to a condition called root rot, which can be fatal for your Pencil Cactus pretty quickly. To avoid this issue, ensure that your plant is never left in standing water.

Tip: Always check the moisture level of the soil before watering your Pencil Cactus. If the top layer of the soil is dry, it is time to water.

Following a regular watering schedule is not recommended for the Pencil Cactus. Instead the frequency of watering should be determined by the plant’s environment and the season. This means some months you’ll be watering more than others. Here’s a general guideline to help you get started:

  • Summer: Water your Pencil Cactus once every two weeks. The warmer temperatures will cause the water to evaporate quicker.
  • Spring and Fall: Watering once a month is usually sufficient. These seasons have milder temperatures, so the soil stays moist for a longer period.
  • Winter: Limit watering to once every 6 weeks. The plant is dormant during this season and requires less water.

Remember, these are just guidelines. You should always check the soil’s moisture level before watering.

Pencil Cactus Humidity Requirements 

The Pencil Cactus thrives in dry conditions and it’s not a big fan of high humidity levels.

Generally, the Pencil Cactus prefers humidity levels that range between 40% and 50%. Anything significantly higher or lower can potentially stress the plant, leading to yellowing of leaves or drooping growth.

How to Monitor Humidity Levels

The easiest way to monitor the humidity around your Pencil Cactus is by using a digital hygrometer. This device measures the relative humidity in the air.

Does Misting Help?

Unlike many houseplants, the Pencil Cactus does not benefit from misting. In fact, misting can lead to leaf rot and other fungal diseases due to the lingering moisture on the plant. The Pencil Cactus is a succulent, meaning it stores water in its stems and prefers to be dry most of the time. So, it’s best to avoid misting this one!

Temperature Considerations

This plant prefers warmer, desert-like conditions but although high temperatures are not a problem for this succulent, that doesn’t mean it’s completely indestructible.

Daytime Temperatures

During the day, the Pencil Cactus thrives best in temperatures ranging from 70 to 90 degrees Fahrenheit. This warmth mimics the plant’s natural environment, promoting optimal growth and vitality. However, make sure your plant is not exposed to direct, scorching sun rays, as it can cause sunburn to the leaves. This will show up as sickly yellow or brown patches.

Nighttime Temperatures

At night, the Pencil Cactus can handle a drop in temperature. Ideally, keep the temperature around 50-60 degrees Fahrenheit but this plant is versatile and can handle occasional dips below this range. Just ensure it doesn’t get too cold, as frost can severely damage your plant by causing the water stored in the cells to freeze.

Choosing the Best Soil Type

Your Pencil Cactus requires well-draining soil to thrive and the primary objective is to prevent water from pooling around the roots, which can lead to root rot.

Components of an Ideal Soil Mix

A well-balanced soil mix for a Pencil Cactus should include the following components:

  • Coarse sand: This helps improve soil drainage and mimics the natural gritty soil the plant grows in the wild.
  • Peat moss or coco coir: These elements help maintain a certain level of moisture without retaining excess water.
  • Perlite or pumice: They add air pockets to the soil, helping with drainage, aeration and preventing soil compaction.

You can create your own blend at home or purchase a pre-made cactus or succulent mix from a garden store.

Soil pH

Pencil Cacti prefers slightly acidic to slightly alkaline soil, with a pH range between 6.0 and 7.5. Most cactus and succulent soil mixes fall within this range, but it’s always a good idea to check the pH before planting, especially if you’re preparing your own mix. You can easily test the pH using a simple home soil test kit available at most garden centers.

Pencil Cactus Repotting Guide

Repotting a Pencil Cactus plant is a crucial aspect of its care and maintenance. Though these plants are relatively low-maintenance and can thrive in the same pot for years, there comes a time when they outgrow their current home and need a larger space to expand their root system.

Repotting not only provides the plant with more room to grow, but also revitalizes the soil and promotes healthier, more vibrant growth.

When to Repot

Typically, Pencil Cactus plants need to be repotted every two to three years. However, this timeline can vary depending on the plant’s growth rate and the size of the current pot.

Signs that your plant may need repotting include a slowdown in growth, roots growing out of the drainage holes, or the plant becoming top-heavy and tipping over. If you notice any of these signs, it’s likely time to repot.

Repotting Process

  1. Prepare the New Pot: Choose a new pot that is one to two sizes larger than the current one and ensure it has good drainage to prevent waterlogging. Fill the pot with a well-draining cactus or succulent potting mix.
  2. Remove the Plant: Carefully remove the Pencil Cactus from its current pot. It’s a good idea to wear thick gloves to protect your hands from the plant’s spines.
  3. Trim the Roots: Prune any dead or overgrown roots. This promotes healthier growth and helps the plant adapt to its new home more easily.
  4. Place the Plant: Place the plant in the new pot, making sure it is centered and upright. Add more potting mix if necessary, but avoid packing it too tightly.
  5. Water Thoroughly: Once the plant is securely in its new pot, water it thoroughly. This helps settle the plant and the potting mix.

Fertilizing your Pencil Cactus

The Pencil Cactus is a low-maintenance houseplant that requires minimal fertilization but it can be really helpful in low doses to maintain and promote healthy growth.

As a general rule, your Pencil Cactus should be fertilized once every 1-2 months during the growing season, typically from spring through the end of summer. During the winter, it’s best to cut down on fertilization completely, as it’s the plant’s dormancy period and excessive nutrients can actually cause more harm than good.

Choosing a Fertilizer

Opt for a balanced, water-soluble fertilizer. This means the N-P-K ratio — nitrogen (N), phosphorus (P), and potassium (K) — should be equal, such as 10-10-10 or 20-20-20. Nitrogen promotes leaf growth, phosphorus aids in root and flower development, and potassium contributes to overall plant health.

Fertilization How-To

  1. Dilute the fertilizer: Dissolve the recommended dose of fertilizer in water according to the product’s instructions. We often tend to dilute it even more than recommended just to be on the safe side and avoid overdoing it.
  2. Apply the fertilizer: Pour the diluted fertilizer over the soil, ensuring it’s evenly distributed. Remember to avoid getting fertilizer on the plant’s leaves or stems, as this can cause issues if done repeatedly.
  3. Rinse the soil: Every so often, deeply water your Pencil Cactus to flush out any excess salts from the fertilizer.

Propagating your Pencil Cactus

Propagation is a fantastic way to expand your collection of houseplants or share them with friends and family. The process is pretty straightforward thankfully but here’s a brief step-by-step to help you along the way.

Step 1: Choose a Healthy Stem

Identify a healthy and mature stem from your Pencil Cactus. The stem should ideally be several inches long to allow for the best possible start for your new plant.

Step 2: Make a Clean Cut

Using a clean, sharp knife or pruners, cut the selected stem from the plant. Ensure you make a clean cut to minimize damage. It’s important to note that the sap of the Pencil Cactus is toxic, so you should handle it with care and avoid contact with your skin and eyes.

Tip: Always wear gloves and protective eyewear when handling a Pencil Cactus to protect yourself from its poisonous sap.

Step 3: Let it Heal

After you cut the stem, it needs to form a callus over the cut surface before you plant it. This can take anywhere from a week to a couple of weeks, depending on the environmental conditions. Place the stem in a dry, shaded area and allow it to heal.

Step 4: Plant the Stem

Once the cut surface has fully healed, you can plant the stem in a pot filled with a well-draining cacti or succulent mix. Place the stem approximately one inch deep into the soil and firm the soil around it.

Step 5: Provide Appropriate Care

Water the newly planted stem sparingly until new growth appears, and gradually increase watering as the plant grows. Ensure it receives plenty of indirect sunlight and continue caring for it as you have been with the mother plant!

Flowers on a Pencil Cactus

Unlike many other common houseplants, the Pencil Cactus doesn’t follow a routine yearly flowering cycle. Instead, it blooms sporadically and infrequently.

During the blooming phase, the Pencil Cactus produces small, yellowish-green flowers. These delicate blossoms are a sight to behold but are not often seen in typical indoor conditions. The flowers are usually clustered towards the ends of the plant’s pencil-like branches, providing a striking contrast to its otherwise green hue.

It’s important to know that even with perfect care, some Pencil Cacti may never flower. This is simply due to the plant’s unique and unpredictable blooming nature. Do not worry if your plant doesn’t bloom – as long as there are no signs of distress, this isn’t a cause for concern.

Pencil Cactus Toxicity

The Pencil Cactus contains a milky, latex-like sap within its branches that is highly toxic.

This sap is known to contain various compounds, among them the diterpene ester phorbol, which causes irritation. Contact with this sap can lead to a range of symptoms, some of which are rather severe.

  1. Direct contact with skin: If the sap comes into direct contact with the skin, it can cause irritation, redness and swelling. In some cases, it may lead to a severe rash or burns.
  2. Eye exposure: If the sap gets into the eyes, it can cause severe pain and irritation. In extreme cases, it can lead to temporary or permanent blindness.
  3. Ingestion: If ingested, the sap from the Pencil Cactus can cause vomiting, abdominal pain, and in severe cases, it can even impair the respiratory system leading to difficulty in breathing.

As they are toxic plants, it’s crucial to handle the Pencil Cactus with care. Always wear gloves when pruning or handling the plant, and ensure it’s kept out of reach from children and pets. In case of accidental exposure to the sap, immediately wash the affected area with water and soap and seek medical attention if symptoms persist or are severe.

Pruning and Trimming Techniques

When to Prune

Generally, the best time to prune your Pencil Cactus is during or just before its growing season, which is typically in the late spring to early summer. However, if you notice any diseased or damaged branches, it’s advisable to prune them immediately, regardless of the time of year.

Pruning Techniques

Begin by inspecting your plant thoroughly. Look for branches that are overgrown, discolored, or damaged. Once you’ve identified the branches that need to go, follow these steps:

  1. Put on protective gloves: The sap of the Pencil Cactus is toxic and can cause irritation, so it’s crucial to wear gloves before you start pruning.
  2. Use a sharp, sterilized pair of scissors or pruners: A clean cut helps the plant heal faster and reduces the risk of disease.
  3. Make a clean cut at an angle: This allows the sap to drain out instead of pooling at the cut, which could lead to rot.
  4. Dispose of the cut branches carefully. Don’t compost them, as the sap can linger and potentially harm other plants or animals.

Pencil Cactus FAQs


Common Problems with your Pencil Cactus

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