The Q&A Archives: Diffenbachia hybrid (SP)

Question: A few weeks ago I bought a beautiful, very green Deffenbachia sp. We watered it and put it in a bright spot that receives no direct sunlight. Within a few days the leaves looked very yellow and spotty. I thought that we overwatered so I left it alone until the soil dryed out. Now the plant is very brown and the leaves are brittle in the brown spots. I am watering sparingly. There are some new leaves opening and they are mostly green but one or two is yellow and they have some brown spots. I brought the plant home on a cold January day in Chicago - but the plant was outside for about thirty seconds. what am I doing wrong?

Answer: Based on your description, there are several possible causes for the leaf problems. To certain extent, the plant will simply be stressed by being moved to a new location and it will need some time to adapt. Under ideal circumstances, this plant likes it warm and humid with moderate indirect light.

Cold temperatures are detrimental to this plant, with actual damage occuring at about 50 degrees, so that certainly may be part of the problem. Try to give it a warm household temperature of about 70, with ample humidity and good air circulation (but keep it away from drafts, both hot and cold.)

A location near a heat vent or radiator during winter heating system is going to create a warm dry draft that is especially detrimental. Close proximity to a window pane can also create an especially cold microclimate.

This plant is adapted to lower light levels, so it is possible it is in too bright a location. A northern exposure or back a few feet from an eastern window, or using a filtered curtain can all be beneficial.

The soil surface should begin to dry a bit between thorough waterings with tepid water. Do not allow it to go bone dry as drought conditions can cause foliage dmage. Avoid saturating the soil (can cause root rot issues) and be sure to empty any excess collected in the drainage saucer under the pot. Use your finger to check the soil and see when you need to water next.

Overfertilizing can cause foliage issues. Most newly purchased plants do not need feeding for a month or two after purchase. Then use a water soluble fertilizer for foliage plants (such as 10-10-10 plus minors) at the weaker rate on the label about once a month.

This plant is sometimes affected by spider mites. Check the plant for signs of fine webbing in the joints where leaves meet the stems and on the undersides of the leaves and along the stems. This pest causes a dry-looking leaf much as you described. If you find this webbing, treat (and repeat treatment) with commercially formulated insecticidal soap per the label directions, being sure to spray all surfaces of the plant thoroughly. You can also rinse the plant with tepid water about once a week to help keep these at bay. They tend to surge during the dry winter heating season and humidity helps reduce their numbers. Using a humidifier or pebble and water tray to humidify the air near the plant can also be helpful. Also, remove the worst affected leaves and dispose of them in the trash to limit sources of reinfection.

I hope this helps you trouble shoot.

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