Pencil cactus: location, care & propagation of Euphorbia tirucalli

The pencil cactus (Euphorbia tirucalli) is a low-maintenance succulent with an unusual appearance. Here are tips on how to properly handle the plant.

Like most succulents, the pencil cactus is a relatively undemanding plant. However, some care should be taken when handling the plant due to the toxic milky sap that can come out at cut sites. Find out here what else you should pay attention to when it comes to location and care.

Pencil cactus: flower, origin and properties

Pencil cactus (Euphorbia tirucalli) is also known as pencil tree, Indian tree spurge, or milk bush. Originally, the plant comes from the southern and eastern regions of Africa, and today – thanks to its low maintenance – it is very popular as a houseplant. Euphorbia tirucalli belongs to the spurge (Euphorbia) genus within the spurge family (Euphorbiaceae). Like numerous species of this plant family, the pencil cactus contains a milky sap that oozes when the plant is injured. This milky sap is toxic and corrosive in the case of Euphorbia tirucalli, so a safe location should be selected for the plant.

The pencil cactus consists of green and fleshy, but narrow branches that give it a special appearance. The leaves can store water to survive dry periods. The leaves on the shoots are small and inconspicuous and are usually quickly shed. In the wild, the plant also grows small, yellowish flowers between June and August, which are located at the ends of the branches. While indoor shrubs grow only about 80 cm tall, pencil cactus also reach heights of up to 10 metres in nature.

Tip: In addition to the classic green milk bush, there is another interesting variety, also known as the “Stick of Fire”: the shoots of Euphorbia tirucalli ‘Rosea’ are a fiery red and give the plant a special appearance.

Growing pencil cactus: location, timing and procedure

When choosing a location for the pencil cactus, the main thing to ensure sufficient sunlight. Since Euphorbia tirucalli requires direct sunlight, it should be placed by a south-facing window, for example. This usually also provides sufficient heat because the pencil cactus does not tolerate temperatures below 12 °C. In summer, the succulent can also be placed in a bright place outdoors.

When it comes to substrate, the pencil cactus is somewhat more demanding: to avoid waterlogging, the planting soil should be permeable and well drained. You can use cactus soil for the pencil cactus.

Tip: If you water less often, the pencil tree can also be planted in universal compost. It is best to regularly check whether the plant is doing well and that the water supply is suitable.

Care measures

Pencil cactus care is very easy because the plant does not require a lot of water or nutrients. From time to time, however, the pencil tree also needs a little attention. We briefly show what needs to be considered.

When the surface of the substrate has dried, you should water the soil. For watering, rainwater is ideal as it is naturally low in lime, and this will benefit the pencil bush. In summer, watering is done about once a week, and less often in winter. Excess water must be removed from the saucer so that root rot does not occur.

Tip: Limp, drooping branches are a sign of too little water.

The nutrient requirements of the milk bush are rather low. However, during the growing season from spring to autumn, you should provide the fast-growing plant with some fertiliser every four weeks. Our Plantura Liquid Houseplant Food is suitable for this purpose, which you add to the watering water in half concentration.

In winter, the pencil cactus should be allowed to rest. The plant is then kept at about 15 °C in a bright place. Watering is now even less frequent, just enough so that the root ball does not dry out completely. Fertiliser is not necessary during this period. The rest period should be about three months and take place between October and February.

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The pencil cactus can be pruned to restore the shape of older specimens. Pruning is appropriate especially when the plant becomes bare lower down and no fresh shoots are formed. To do this, cut back the shoots by about a third. Be sure to wear gloves to protect yourself from the milky sap that escapes during pruning, and clean all equipment afterwards. The pruned areas on the pencil tree can be treated with a damp cloth. It is best to prune towards the end of the dormant period, as less sap will escape and the plant will be able to resprout immediately in the spring. The cut shoots are also suitable for propagation of the milk bushes.

The pencil tree should be repotted every two to three years. Wearing gloves is also recommended for safety here. When the old pot is fully rooted it should also be repotted into a larger planter.

Tip: A layer of pebbles on the bottom of the planter ensures adequate water drainage and avoids waterlogging.

Propagating pencil trees

Cuttings are best for propagating the pencil cactus. To do this, in the spring, cut off a few shoots about 15 cm in length, just below the node of leaves. The cuttings are then dried for about two days, so that the cut areas do not rot. Subsequently, they can be placed in nutrient-poor substrate and put in a warm, bright place. Our Plantura Organic Herb & Seedling Compost, for example, is ideal for growing cuttings. The nutrient-reduced soil promotes strong root growth of the seedlings before they grow to height. Our compost consists of natural raw materials and is completely peat-free. Keep the substrate moderately moist to prevent root rot. After about three weeks, roots should have formed so that the little pencil cactus can now be treated like the mother plant. Be sure to wear gloves when propagating to protect yourself from the corrosive milky sap.

Common diseases and pests

Pencil bush is considered a fairly hardy plant and is rarely attacked by pests. If it is still not growing well or looks limp, the cause is usually a location that is too cold or wet. Nevertheless, the following pests may occasionally appear:

• Wool lice, aphids or spider mites: These rarely occur on the pencil tree and then usually only appear when the humidity in the room is low.
• Tube fungi: these are caused by waterlogging, which also leads to root rot and can manifest itself in a yellowing of the shoots.

Tip: The most common pencil cactus care mistake is overwatering, which can cause waterlogging and root rot. In this case, the plant should be immediately repotted in dry, fresh substrate.

Is the pencil cactus poisonous?

The pencil bush is indeed a poisonous plant. This is due to the milky sap in the succulent branches that oozes when injured and is irritating to the skin. Therefore, place the plant out of the reach of pets and children, and always wear gloves when pruning.