Euphorbia tirucalli

The pencil tree is a succulent, spineless shrub or tree that has a unusual growth habit and is native to Madagascar. It has a heavy trunk, brown primary branches, and pencil-like, green, new branches. In its native habitat, this plant can grow up to 30 feet tall and 6 to 10 feet wide. If grown indoors, it will range from 2 to 6 feet tall and 1 to 3 feet wide. It is a member of the spurge family (Euphorbiaceae). The specific epithet, tirucalli, is derived from tiru meaning "good" and kalli that refers to the medicinal properties of this genus. This name was chosen by the Swedish botanist, Carl Linnaeus, from words used by the native people of Malabar in Southern India.

This plant thrives in bright indirect light or direct sun. When grown outdoors, the plant does best in dry climates where the temperature ranges from 50 degrees in the evening and 75 degrees during the day. Plant in well-drained soils that are nourishing but without high organic content. If local conditions include hot summers, it is best to site the plant where there is some afternoon shade. When grown indoors, use coarse loamy soil with peat moss or leaf mold plus gritty material such as coarse sand. Water the plant about every 1 to 2 weeks and allow the soil to dry out between waterings. It is tropical to semi-tropical by nature and reliably winter hardy to USDA Zone 11 to 12.

The new branchlets are green, cylindrical, and pencil thick. They will form clusters at the end of the branch. The leaves are tiny, only about 1-inch long, and fall off very early. The flowers are inconspicuous, tiny, and yellowish. The blooms are located at the top of the branchlets and surrounded by showy bracts that hide the flowers. The milky sap of this plant is very caustic.

It is currently surviving in southern parts of Florida and California in Zone 10. It is drought tolerant and when grown outdoors in warm climates, the tree is typically used as a hedge or barrier. When grown in more temperate climates, it can be kept smaller and used as a houseplant.

Diseases, Insects, and Other Plant Problems: No significant problems. Watch for nematodes, spider mites, aphids, and mealybugs. Fungal and bacterial diseases can appear. Overwatering can cause root rot.

Keep this plant out of reach of children and pets. Wear gloves when working with this plant to avoid contact with its toxic sap. Seek medical attention immediately, if ingested or eye exposure.

VIDEO Created by Elisabeth Meyer for "Houseplants, Succulents, and Cacti", a plant identification course offered in partnership with Longwood Gardens.

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