Dumb cane

Identification and origin

Dieffenbachia seguine belongs to the arum family, Araceae, along with philodendrons and monsteras. Its native range runs from the Greater Antilles (Cuba, Hispaniola, Jamaica, Puerto Rico) and the Lesser Antilles to Trinidad, Venezuela, the Guianas, Colombia, Ecuador, Peru, Bolivia and Brazil. Many plants sold as Dieffenbachia picta, D. maculata or D. amoena are now included in this species.

It is an upright, evergreen herbaceous perennial. The thick, fleshy stem, marked with scars where old leaves fell, branches little and carries its leaves toward the top, which is where the “cane” comes from. The leaves are simple and alternate, oblong and pointed, glossy, with many side veins; they can reach 18 in long and 12 in wide. They are spotted, marbled or veined with cream, white or yellow depending on the cultivar: ‘Camille’, cream edged in green; ‘Tropic Snow’, dark green splashed with cream; ‘Rudolph Roehrs’, pale yellow blotched with white. Indoors it seldom blooms, and the flowers (a white spadix inside a pale green spathe) are not showy.

In a pot it grows 3–6 ft tall in common forms and up to 8 ft in the largest; some compact cultivars stay around 12 in. Spread ranges from 12 in – 3 ft.

Light

Bright but filtered light from spring through fall: behind a sheer curtain or set back from a sunny window. Keep it out of direct sun during the warm months. In winter, when the sun is weak, a brighter spot, even with some direct sun, suits it better. It tolerates shade, which is why it does so well indoors, but growth slows considerably. Turn the pot regularly: a plant lit from one side grows lopsided.

Watering

Water thoroughly, then let the top 1–1 in of the mix dry before watering again. Never leave water standing in the saucer. How often depends on the season, warmth and light: feel the mix rather than following a calendar.

What to watch for: drooping leaves usually mean the plant is thirsty; brown tips point to uneven watering; mix that stays soggy leads to root rot.

Potting mix

Most well-drained container mixes work. It prefers a loose, fertile blend rich in organic matter, acidic to neutral. From spring to late summer, a half-strength foliage-plant fertilizer every two to four weeks (or a slow-release product) keeps it vigorous; too much fertilizer burns the leaf edges.

Temperature

It is happiest between 61–75 °F. Don’t let it drop below 55 °F: if the leaves droop from cold, move it to a warmer room. Protect it from cold air currents and sudden temperature changes.

Outdoors year-round, it can only be grown in USDA zones 10 and 11, where there is no frost. There it can even become invasive: in Florida it is no longer recommended for outdoor planting for that reason.

Repotting

Repot in early spring, only when the plant needs it, into a well-drained mix. Poorly draining mix, like watering too often, rots the roots, so water sparingly afterward and let the surface dry. Wear gloves throughout, because any broken root or stem releases irritating sap.

Pruning

With age, dumb cane naturally sheds its lower leaves and its canes become bare. To rejuvenate it, cut the leggy canes back to about 6 in tall: the plant will resprout. The cut pieces can be used as cuttings. Always wear gloves and keep the sap away from your eyes.

Propagation

In spring or early summer, several methods work: tip cuttings, cane cuttings (sections of thick stem taken from a leggy plant), air layering a stem that has grown too tall, or dividing the clump. It can also be started from root cuttings.

Common problems

• Mealybugs and aphids: they leave sticky honeydew on the leaves.
• Spider mites, scale insects, whiteflies and fungus gnats: check leaf undersides and the surface of the mix.
• Root rot: overwatering or poor drainage.
• Leaf spots and blight caused by fungi.
• Curled leaves with brown edges: too much fertilizer.
• Yellowing, smaller leaves and stunted growth: nutrient deficiency.
• Very slow growth: not enough light.
• Leaves drooping without yellowing: thirst, or a room that is too cold.
• Lower leaves falling: normal with age.

A symptom rarely has a single cause: always weigh watering, light, temperature and feeding together before drawing conclusions.

Toxicity

Highly toxic to people and animals. All parts contain raphides, needle-shaped calcium oxalate crystals, along with a protein-digesting enzyme. Chewing the plant immediately causes burning, numbness and swelling of the lips, tongue and throat, heavy drooling, and difficulty swallowing and speaking (hence the name “dumb cane”), followed by nausea, vomiting and diarrhea. Throat swelling can interfere with breathing. The sap irritates skin and can damage the cornea if it gets in the eye. In dogs and cats it causes intense burning and irritation of the mouth, drooling, vomiting and difficulty swallowing; poisoning can be serious for pets. It is not recommended in homes with young children or curious pets; if any is swallowed, call Poison Control or a veterinarian right away.