How to Grow and Understand Dumb Cane (Dieffenbachia)

Not Your Average Houseplant

Dieffenbachia Maculata
Wikimedia Commons

The dieffenbachia is a beautiful if sometimes confusing group of plants. These plants feature pointed, broad leaves in a variety of combinations of green and white. There are at least a dozen varieties, with names like D. picta, D. amoena, and D. oerstedii. A large, well-grown dieffenbachia can reach five feet, with leaves of a foot or more. However, the plants will rarely reach this size in typical indoor conditions.

The so-called dumb cane gets its name from its milky sap, which is a mild irritant and should be kept from bare skin. The sap can cause temporary loss of speech. These plants are a good option for gardeners with the space to grow them, but consider avoiding dieffenbachias if you have small children or pets around the house. Otherwise, they could be hurt by the irritating substances produced by the dumb cane plant. 

Growing Conditions

  • Light: They appreciate bright light during winter months. During the growing season, the plant prefers dappled shade or indirect light.
  • Water: During the growing season, they like regular moisture and do not want to dry out. A large dieffenbachia might need to be watered twice a week. In the winter, cut back water.
  • Soil: Use a fast draining, well-aerated potting mix. Make sure their drainage is good to avoid damaging the roots; they should never be left in soggy soil or else the plant risks destruction.
  • Temperature: They like above-average warmth. If the temperature drops below 60 degrees or the plant is exposed to cold drafts, it is likely to lose lower leaves and gain a "palm" effect.
  • Fertilizer: Feed regularly with a balanced, diluted fertilizer like a 20-20-20 for best results.

Propagation

There are several possibilities:

  • During repotting in the spring, offsets can be divided (leaving some roots intact) and planted in their own pots. If you take this route, make sure not to damage the root systems of the parent plant in the process, and consider using a sterilized tool to avoid disease.
  • In older, leggy dieffenbachia, the top can be cut off and potted into fresh potting soil with a rooting hormone. New leaves will sprout from the stump.
  • Pieces of the cane can be sprouted by laying them horizontally in damp potting soil

Repotting

Repot annually for best results, simply by lifting the plant as a whole, knocking away any old soil and dead material from the roots, and replacing it in a larger container. Watch out for signs of stress on the plant, like roots poking out from the surface, crowding, or falling leaves, which could signal that the plant needs repotting. After repotting a dieffenbachia, give it some time to adjust to its new settings before you affect it too much. And make sure to wear thick gloves, or else you risk hurting yourself on the surface of the plant.

Grower's Tips

These are great plants, much favored by interiorscape companies who use them either as singular specimen plants or as massed plantings to great effect.

They are not, however, very easy plants to maintain over the long-term as some varieties are extremely sensitive to drafts and lower temperatures. Look for D. ​picta or D. amoena varieties, such as Tropic Snow, Camilla, or Marianne. Remember to wear gloves when exposure to the sap is possible, especially near the mouth. Dumb cane sap has been known to cause temporary loss of speech (hence the name). This plant is best recommended for experienced gardeners who have the skills to keep it alive and help it flourish. Watch out for common houseplant pests like scale and spider mites, which cause exterior damage. In small-scale cases, they can be simply wiped away manually, but a more significant infestation could require the use of a good strong pesticide.