About 3 weeks ago, I purchased this plant in about a 6″ pot. I water it almost daily. It seems that the plant sucks up the water right away, but it seems to drain out the bottom quickly too. (It’s in the same pot from HyVee). A few of the leaves are turning yellow and brown on the tips. I will also add that although I have it in the window of indirect sunlight, it’s winter in the Midwest so it’s been pretty glum since I bought it. We haven’t had a full sunny day yet! Is it simply the lack of a sunny day, or am I doing something else wrong?
Tip yellowing and browning on Dieffenbachia leaf tips is a generic reaction to improper light or watering.
Dieffenbachias prefer lots of bright, but indirect sun light. If yours is right in a windowsill and the window is completely uncovered during the day, then it should be getting enough light even if the weather is cloudy.
The reason the water seems to run straight through is because the soil is still saturated from the previous watering. It should not require water more than once or twice per week. The top half inch of soil should feel very dry before you add any water.
Any leaves that have already discolored will not recover and can be trimmed off. As long as new leaves that emerge remain healthy, then you are on the right track. Normal aging will cause some discoloration of older, lower leaves.