Question
I have a Dieffenbachia and it is about 5ft. The top half is full and the leaves are spread out nice. The bottom half on the other hand is drooping way down and the leaves are starting to turn yellow.  I keep it in the kitchen about 4ft from the window.  It is growing new leaves all the time, but the more that grow the more I pull from the bottom because they droop and then turn yellow then wilt. About two feet of it has no leaves at all. I cut it once because of this problem and the new cut is growing ok. The stem is also very skinny. Will my new growth have a bigger stem?  What can I do to stop this problem? Should I cut it back again? Please help.

Answer
This is a very common problem with Dieffs. And the most common solution is to cut the top off, and start over again.
Because the stem that is bare will not produce leaves again, it will soon be a tall, bare, umbrella. It may, however have new grow come from the bottom. Try to encourage that new growth.  When I saw new growth on my tall plant, I cut the old stem off and used the new growth until it did the same thing as the old one. I am looking for new growth on that one to start, and then, I will do the same thing.
I have not tried it, but I have read that you can cut a small slit at the base of the plant, near a leaf node, and the new growth will start from there.
You may try moving it closer to the light, so that it is not stretching as much, causing the elongated stem. Cut back on the water, only water when the soil is dry, and don't fertilize until June, and don't allow drafts or cool temperature. They are very temperature sensitive. They will tolerate low light, but will be thicker and stronger in bright light. This will slow the growth, and cause it to go winter dormant. You want it to go dormant. Much of the problem is the top is growing faster then the roots can support. By slowing that growth the stress will be reduced and so will the yellow leaves.
Tip: Always be very careful when handling these plants. The sap is poisonous. Wash your hand thoroughly after touching it.