Fire Stick (Euphorbia tirucalli) — identification, habitat & look-alikes

Pencil cactus, or firestick, isn't a cactus at all but a succulent from Africa with pencil-thick green branches. It grows outdoors in frost-free parts of southern Florida, Southern California, and Hawaii, and is a popular houseplant elsewhere. Its milky sap can burn skin and seriously injure eyes. It's also called milk bush.

Appearance

Appearance: Outdoors it can become a tree up to about 16–30 ft (5–9 m) tall, but indoors it usually stays 2–6 ft (0.6–1.8 m). Smooth, spineless, round green branchlets cluster at the branch tips.
Leaves: Tiny leaves, about 0.4–1 in (1–2.5 cm) long, drop off early, so the plant looks leafless.
Flowers: Small yellowish flowers sit at the branch tips and are easy to overlook.
Fruit: A three-lobed capsule about 1/2 in (12 mm) across, pale green blushed pink, that splits open when ripe.

Look-alikes

Whisk fernPsilotum nudum

Whisk fern is small, about 1 ft (30 cm), with stems that fork in twos and tiny yellow spore cases along the branches. It never flowers and has no milky sap.

Why they get mixed upBoth look like bundles of leafless green sticks.

Mistletoe cactusRhipsalis baccifera

Its very thin stems (under 1/4 in, 0.5 cm) hang down from trees or baskets, and it makes white flowers and small white to pink berries.

Why they get mixed upBoth have slender, round green stems in dense clusters.

Where it lives

Typical habitats: Dry tropical savanna
Gardens
Houseplant
Range: Native to dry parts of Africa and Madagascar, and introduced across the tropics. In the US it grows outdoors in Hawaii and survives in the mildest parts of southern Florida and Southern California.
Preferred conditions: Reliably hardy only in USDA zones 11–12, though it survives in zone 10 in southern Florida and California; it can't take frost. Likes full sun to bright indirect light and sharply drained soil.

Growing it

Care: Water every 1–2 weeks and let the soil dry out in between; too much water causes root rot. Used outdoors as a hedge or barrier in warm, dry gardens.
Toxicity: All parts ooze a milky that causes painful skin rashes and, in the eyes, intense pain and possible temporary blindness, so get medical help right away if it gets in your eyes. Swallowing it burns the mouth. Wear gloves and eye protection when pruning, and keep it away from kids and pets.

Name and classification

Varieties and forms: 'Sticks on Fire' has reddish-gold stems that color up most in winter.

Conservation

IUCN Red List: LCLeast ConcernLow risk of extinction
Status: Listed on CITES Appendix II, like most succulent spurges.

Culture and stories

Culture and stories: Chemist Melvin Calvin promoted it as a possible "petroleum plant" because its latex is rich in oils, and Brazil's oil company tested it in the 1980s, without much success.