Dieffenbachia

Species pages start from this and record only where they differ.

Light

Bright indirect, no direct midday sun — but the useful number here is the floor. UF/IFAS puts the minimum interior light at 150 foot-candles, lower than anything else on this site. Rotate the pot every few days; it stretches unevenly towards a window.

Water

Water through, then let the top 2-3 cm dry completely before the next one. Never leave the pot standing in water — that, not dry air, is the first thing to check behind brown leaf tips. Keep water off the foliage: the bacterial problems all travel in splash.

Humidity

It likes humidity and will take plenty, but no extension service or paper gives a figure for this genus, and the percentages circulating online come from sellers who do not agree with each other. The rule that matters more than a number: humidity without air movement is exactly what Erwinia soft rot wants.

Temperature

65-80 °F (18-27 °C) year round, floor 60 °F (16 °C). Below 55 °F (13 °C) expect drooping and leaf drop, and anything from just above 32 °F to 59 °F (0-15 °C) can cause chilling injury on a warm-grown plant.

Substrate

Any good free-draining potting compost opened up with perlite or bark. UF/IFAS asks for two things only — good aeration and low soluble salts — and names no recipe. It is terrestrial, so it does not want an epiphyte chunk mix.

Fertilizer

A balanced or high-nitrogen liquid feed at label rate, monthly in growth, and scaled to the light: UF/IFAS feeds a plant in a dim corner at roughly half the rate of one in a bright room. Curled leaves with brown edges is over-feeding.

Propagation

Tip cuttings, cane sections laid flat on warm compost at about 77 °F (25 °C), or air layering — a bare leggy trunk is not a lost cause. Gloves and eye protection: cutting a cane is the highest-exposure thing anyone does with this plant.

Dormancy

None, and the evidence runs the other way — cold in this genus is documented as injury rather than rest. Growth slows in low winter light, so water and feed less, but keep it warm.

Common problems

• Erwinia blight and soft rot is the signature disease: lower leaves yellow, spots go mushy and often smell. Favoured by warm, humid, still air — the controls are ventilation, dry foliage and clean tools
• Xanthomonas leaf spot shows as almost-black spots with a yellow halo spreading from the leaf edge. It is the same pathovar as Anthurium bacterial blight, so do not share tools or drip trays between the two
• Two-spotted spider mite is the main insect pest, with aphids, mealybugs, scale and thrips behind it
• Stem and root rots — Fusarium, Phytophthora, Myrothecium — enter through wounds and wet tissue. Keep pots off standing water and sterilise between cuts
• Chilling injury is chlorosis, water-soaked patches and reddish-brown stem collapse, newest growth first. It appears after a cold night and does not spread, which is how you tell it from disease
• The sap is the problem that defines the genus: burning and swelling of the mouth, drooling, difficulty swallowing and speaking, dermatitis on skin, corneal damage in an eye. NC State rates the species poison severity High. Gloves to prune, and keep it away from children and pets

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In the collection