Question
I just bought two diffenbaccias home andthe leaves are turning brown. The soil is moist and I was about to repot them, but I am concerned they might be diseased. I cut all the leaves off that are browning, but I think it may be systemic. What can i do? Thank you.

Answer
Denice,

Browning on dieffenbachia leaves is usually caused by either too much water or too much sun. The plant should be well watered then not watered again until until the top 2 inches of soil is totally dry. There will still be moisture lower in the pot. This plant also hates the sun, it needs bright light but no direct sun shining on its leaves.

I also do not reccommend that you repot any new houseplant until it has been in your home for a year. Most plants like to be somewhat rootbound. If you really want to repot it do not increase the size of the pot. Put it in a pot  the same size as the pot it cam in or absolutely no more than 2 inches larger in diameter. Too large a pot will kill a plant because you will overwater it. If you are combining 2 plants into one pot and they both came in 6 inch pots put them together in no larger than a 10 inch pot. Right now keep your dieffs in the pots they came in and let them dry out better between waterings and move them to a location with bright indirect light. If you sitll think you have a fungal problem spray them lightly once a wee with Lysol type spray  getting the fronts and backs of all the leaves. Do this for a month and see if the plants are looking better then repot them if they are looking better. Good luck.

Darlene