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Cacti & Succulents, Specific Houseplants

Pencil Cactus Care: How To Grow Firesticks


10 min read

If you’re looking for a succulent houseplant to make a striking statement, look no further than the pencil cactus or Euphorbia tirucalli. This firecracker of a plant goes by many names: aveloz, firestick plant, Indian tree spurge, naked lady, and milkbush.

That last name refers to the cloudy latex sap it releases if it’s damaged, which can be toxic. But with a little precaution, you can successfully plant, cultivate, and enjoy a pencil cactus plant in your home or landscape.

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Pencil Cactus Quick Care Guide

The gorgeous firestick plant has a strikingly unique visual appeal
The gorgeous firestick plant has a strikingly unique visual appeal. Source: Dallas Krentzel
Scientific NameEuphorbia tirucalli
 Common Name(s)Pencil cactus, aveloz, Indian tree spurge, naked lady, pencil tree, pencil plant, and milk bush
FamilyEuphorbiaceae
Height & SpreadGrow up to 30′ high
SunFull, bright sun all day
SoilA gritty and well-draining soil
WaterLow
Pests & DiseasesRoot rot, phomopsis, spider mites, mealybugs, aphids

All About the Pencil Cactus

Belonging to the Euphorbia family, pencil cactus grows in a variety of shapes within an indoor landscape. It can grow up to 30 feet high in its natural habitat. E. tirucalli Sticks on Fire has vertical stems and loose branching. It is as thin as pencils and has a reddish-golden color that turns to yellow in late spring and early summer and then red in winter. Firestick plant grows up to 4 to 8 feet and 120 to 240cm wide in homes if provided with full sunlight and a frost-free climate.

It is called a pencil cactus plant because of the diameter of the stem, which is equivalent to a pencil. The new branches in the plant are slightly pink. You may see leaves appearing as the branches sprout. But they disappear once the branch matures.

Leaves, you ask? Well, turns out the pencil cactus plant is not actually a true cactus but a succulent. The leaves of the plant form but fall off almost right after they mature. That being said, the stems of Euphorbia plants are not technically stems, but modified thorns. The concept of modified thorns becomes clearer if you think about the botanical structure of other Euphorbias, like the Christmas cactus, Easter cactus, or Thanksgiving cactus.

There are commercial uses of Euphorbia tirucalli, too. Since it is a hydrocarbon plant, it can produce latex that can be modified and converted into an alternative of gasoline. It can also be used in the production of rubber. Additionally, the pencil cactus plant can be grown in soil that is not great for growing other plants.

The plant has a wide distribution across Africa and India and is more prominent in the northeastern, central, and southern regions. The cultivation of pencil cactus extends to the Arabian peninsula and the surrounding islands. Pencil cactus grows in dry areas with low humidity and is typically used for feeding cattle, funnily enough!

The milk bush makes an amazing houseplant, with the striking stems contrasting most indoor plants quite well. However, because of the milky sap latex the plant produces, it is toxic to pets and humans. If you have curious children or pets, keep these plants away from them. In that same vein, wear gloves, eye protection, and a long-sleeved shirt when you handle or repot yours.

Pencil Cactus Care

Here you can see ants on the flowers of Euphorbia tirucalli
Here you can see ants on the flowers of the milk bush. Source: KHQ Flower Guide

Firestick plant has very simple needs. It doesn’t have very particular soil, water, or fertilization requirements.

Light

Pencil cactus requires full sun for optimal growth – at least six hours per day. If you’re indoors, right next to a south-facing windowsill is your best bet. Mild and warm temperatures, ranging between 65°F to 70°F, are best for growth. In cold spells, ensure your cactus is indoors when the temperature dips below 50°. Keep it out of cool drafts. On the other hand, heat is mostly not a problem for your cactus, as it can withstand consistent 100° weather.

Water

Being succulents, they can store water in their fleshy stems and leaves, meaning pencil cactus prefers not much water at all. Water it with fresh water once every 2-3 weeks in the summer when the top inch of soil is dry and maybe once a month in the winter. During cold spells, you don’t need to water it at all.

Soil

If you grow pencil cacti in your home as an indoor houseplant, make sure to have gritty and well-draining soil. The excess moisture needs to drain from the soil. Otherwise, there will be a risk of rotting out the roots, the most common houseplant issue. Grow pencil cactus in a preformulated cactus soil, or create your own cactus soil with peat moss, coarse materials, and amendments. Sandy soil is fine. Compacted soil is a no-go.

Pencil Cactus Fertilizer

Stick plants can be fed with a controlled-release fertilizer at the start of the growing season. You can apply it with a weak liquid solution weekly. Using a balanced 20-20-20 fertilizer at one-quarter strength can be applied for large, mature outdoor plants. Most soils will do fine with a 6-4-6 fertilizer. Your pencil cactus prefers no fertilizer in fall and winter when it’s dormant.

Pencil Cactus Propagation

Euphorbia firesticks are easy to propagate, like many of their fellow succulents. You can propagate stick cactus with some cuttings taken from the new or healthy stems. This pencil cactus cutting develops tiny roots. Make sure to wear gloves and eye protection when you cut into the cactus. Dry your stem cuttings out before planting them in new cactus mix. Otherwise, the cut end will rot in the soil before it can set out new roots. Water them in lightly, and then don’t water until the top 2 inches of the soil dry out. Your cutting should form roots and new growth in about a month.

Repotting Pencil Cactus

Every year or two, you will need to repot your plant. Search for a pot size that’s about 1 to 3 inches wider than the root ball of the cactus to be repotted, with adequate drainage holes. Gently remove the entire plant with the root ball intact. Gently separate some of the roots, and fill your new pot with fresh cactus soil. Then place the plant within and top it off. Water lightly.

Pruning Your Pencil Cactus

Frequent pruning is not required for stick cactus. If it starts growing too big, you can trim some branches to cut it back to a more manageable shape. The sap is toxic, so wear a good pair of work gloves and avoid direct contact with the sap on any part of your body.

Troubleshooting Pencil Cactus Issues

Also known as Quebradura or pencil cactus, here you can see the plant making a statement in the landscape
Also known as Quebradura or pencil cactus, here you can see the plant making a statement in the landscape. Source: Alejandro Bayer

While the pencil cactus isn’t typically prone to growing problems, pests, or diseases, there are a few to look out for. Let’s discuss those now.

Pencil Cactus Growing Problems

Overwatering the sticks on fire plant can be troublesome. If you overwater the plant and the soil has poor drainage, you’re going to get root rot underneath the soil. Make sure to water the plant very infrequently, especially when the weather isn’t hot. Check the soil moisture and only water if you find it completely dry. Consider using a looser-textured mix if you find your soil holding on to too much water.

Low light conditions can cause chlorotic, yellowing leaves on your cactus. In this case, move it to a spot with more sunlight, or provide a grow light.

Diseases of Pencil Cacti

Phomopsis is a fungal condition that can develop on your pencil cactus. It’s caused by the fungal pathogen Phomopsis juniperovora, which spurs the development of gray, recessed tips on your pencil cacti. The fungus spreads through wind, rain, and infected soil. Overwatering creates conditions where the fungus proliferates. If this disease appears, wearing gloves, cut off the infected tip with a sterilized pruning knife, and dress the wound with sulfur.

Root rot is a disease that develops when growing conditions of your pencil cactus plant are improper. It causes soft and browning cacti bases, and leaves. You can try to remove the damaged areas and repot your pencil cactus into fresh cactus soil. If the situation doesn’t improve after that, you’ll have to dispose of the cactus altogether as there is no cure for root rot.

Pests

Aphids, mealybugs, and spider mites are all common pests of house plants, which is what most pencil cactus plants are. Each of these congregate on your succulent and suck the plant juices, causing leaf tips to curl, dead stems, and leaf drop in extreme cases. Treat them first by wiping them off your cactus with a damp cloth. You can follow up with a cloth soaked in rubbing alcohol to finish the job.

Frequently Asked Questions

Pencil cactus
Pencil cactus. Source: Starr

Q: How do I know if I am overwatering pencil cactus?

A: You can check the moisture of the plant by examining the soil and studying the appearance of the cactus. If you find the soil soggy, it means either you have overwatered the plant or have poor draining soil. The signs of overwatering are a less stable cactus plant with grayish-brown colored stems

Q: When is the best time to fertilize firestick plant?

A: The best time to fertilize the plant is during the summer growing season. Use an organic houseplant fertilizer and apply once a month for healthier growth.

Q: Is a pencil tree plant suitable for growing in pots?

A: Yes, you can grow the plant in pots. Make sure the pot has drainage holes, and potting mix suitable for cacti and succulents is used.

Q: How poisonous is a pencil cactus?

A: The latex within the plant’s stems can irritate human skin and cause distress if consumed by pets and humans. Keep it out of reach of curious pets and kids.

Q: Can pencil cactus take full sun?

A: Direct sun is great for your pencil cactus. At the very least, provide bright light from an east-facing window.

Q: Can pencil cactus survive winter?

A: It cannot. Therefore, keep it indoors when temperatures reach 50°F or less.

Q: Does a pencil cactus flower?

A: While there are scientific studies that cite a pencil cactus bloom, it’s not common in domestic situations. Most likely, it flowers in its native habitats in Africa and India.

Q: How often do you water a pencil cactus?

A: As a general rule, only water when the top inch of soil is dry.

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