Dieffenbachia (dumb cane)

About Dieffenbachia (dumb cane)

Dieffenbachia is a bold, cane-stemmed foliage plant from the Caribbean and tropical South America with big oblong leaves splashed in cream, white or yellow (NC State). It grows fast in bright filtered light and makes a 3-6 ft floor plant. Its name, dumb cane, comes from the sap: needle-like calcium oxalate crystals numb and swell the mouth and throat and can take away speech, so it is the most poisonous plant in this group and a poor choice for homes with toddlers or chewing pets (Clemson, NC State).

Hardy outdoors only in zones 10-11 (NC State); it is grown indoors everywhere and can summer outdoors in shade once nights stay above 60 F.

When to plant

Timing is counted from your average last spring frost (and first fall frost). Sow & Tell works out the actual dates for your ZIP code.

Usually bought as a nursery plant or started from a cane or tip cutting taken in spring or early summer (Clemson).

Growing it indoors

• Light: Bright filtered light spring through fall, with some direct sun welcome in winter; it tolerates low light but grows slowly there, and darker-leaved kinds take dim rooms best (Clemson, Penn State).
• Water: Water thoroughly, then let the top inch of mix dry completely before watering again (Clemson, NC State); overwatering and poor drainage cause most dieffenbachia problems. Water less in fall and winter when growth slows.
• Humidity: Prefers high humidity (NC State); a pebble tray or grouping with other plants helps in winter.
• Temperature: Ideal 60-75 F; protect it from cold drafts and sudden temperature changes (Clemson).
• Feeding: A foliage houseplant fertilizer at half strength every 2-4 weeks from March through September, or a time-release fertilizer per the label, and none in winter; too much burns the leaf margins (Clemson).
• Repotting: Repot in early spring when roots fill the pot, one size up in a loose, rich mix (Clemson).

Soil

A loose, fertile potting mix high in organic matter with good drainage (NC State).

Pot in a loose, fertile mix high in organic matter with good drainage (NC State).

Feeding

• March through September: foliage houseplant fertilizer at half strength, or a time-release fertilizer. Liquid feed every 2-4 weeks at half strength, or apply time-release fertilizer per its label (Clemson).
• October through February: none. Stop feeding while growth slows for the winter (Clemson, Penn State).

Too much fertilizer burns the leaf margins, while too little gives small yellow leaves and stunted growth; half strength on schedule is the middle path (Clemson).

Varieties (9)

NC State and Clemson Extension name 9 cultivars.

Pests to watch for

Twospotted spider mite, Scale insects, Whiteflies, Fungus gnats, Aphids, Mealybugs

Diseases and problems

Root and crown rot, Fungal leaf spot, Blight

In the kitchen

Safety: Highly poisonous (NC State): all parts carry needle-like calcium oxalate crystals and oxalic acid. A bite causes burning and swelling of the lips, tongue and throat, loss of speech, trouble swallowing and vomiting; a swollen throat can block breathing, so get medical help at once (Clemson). The sap gives a skin rash and can damage the cornea if it gets in an eye, so wear gloves and wash up after pruning. Clemson doesn't recommend it in homes with children or pets.

Pets: Toxic to dogs and cats (ASPCA): insoluble calcium oxalates and a protein-digesting enzyme cause oral irritation, intense burning of the mouth, tongue and lips, heavy drooling, vomiting and trouble swallowing. NC State also lists it as a problem for horses.