Culture
Tropical to semi-tropical tree or shrub that is reliably winter hardy to USDA Zone 11, but is currently surviving in the far southern parts of Florida and California in Zone 10. This plant is typically grown outdoors in the type of soils loved by desert cacti, but with less arid conditions. Prefers dry to dryish atmospheric conditions in sharply-drained soils that are nourishing but without high organic content. Plants can grow in full sun but appreciate some part afternoon shade in hot summer conditions. Avoid excessive watering. Best performance typically occurs when daytime temperatures do not exceed 75°F. and nighttime temperatures do not dip below 50°F.
Container plants perform best in coarse loams enriched with a fairly liberal amount of peat moss or leaf mold plus additional gritty material such as coarse sand, perlite, or broken clam shells. Bonemeal is a good additive.
Noteworthy Characteristics
Euphorbia tirucalli, commonly known under a large number of common names including Indian tree spurge, milk bush, pencil tree, finger tree, aveloz or petroleum plant, is a dioecious, single to multiple trunked, succulent, cactus-like, milky-sapped tree that typically matures to 20-30’ tall with a spread to 10’ wide. It lacks spines and is generally considered to be the least cactus-like of the tree spurges. It is primarily native to semi-arid tropical parts of eastern and southern Africa, but was introduced with subsequent naturalization occurring many years ago along the Arab trading routes from the Arabian Peninsula across the Indian Ocean to India and Indonesia. It typically develops a heavy trunk with thick primary branches which are woody and brown. New branchlets are green with a short cylindrical shape having a pencil-like thickness, often forming clusters at the branch ends. Cyathia (flower structures) are located at the tops of the branchlets in stalk-less clusters, featuring large petal-like showy bracts which typically hide the inconspicuous tiny yellowish flowers within. Tiny leaves (to 1” long) are oblanceolate.
This plant effectively grows in tropical to semi-tropical climates as a shrub, screen or hedge plus indoors in more temperate climates as a houseplant. Plant parts contain a milky sap which is poisonous if ingested and will often cause on contact a variety of allergic reactions to skin and eyes, including temporary blindness. Wear gloves when working with this plant to avoid contact with its toxic sap.
Species plants are currently being touted in some circles as being a potential medical treatment for cancer.
Additional potential uses include being a source of oil (some claim that plants might be capable of producing 10 to 50 barrels of oil per acre) which technically translates into the further claim that a planting the size of the State of Arizona could meet current yearly requirements for gasoline in the U.S. on a yearly basis.
Genus name probably honors Euphorbus, physician to the King of Mauretania.
Specific epithet comes from the Indian-Malayalam names of tiru meaning good and kalli meaning medicinal plant qualities.
Problems
Some susceptibility to nematodes, spider mites, aphids, and mealybugs. Fungal and bacterial diseases may appear.
Uses
In tropical or semi-tropical climates, it may be grown outdoors as a specimen or background plant. It is also effectively grown as a shrub, hedge or screen. Interesting addition to desert gardens.
Where not winter hardy, it may be grown indoors as a houseplant.