1) water roots are not stable when placed in soil ...& they die & so may the stem.... this true for all plants
2) apply o.1% IBA (rooting hormone) stick in well drained, but moist soil & mist 1-2 time a day if needed
3) If you must start in water watch carefully for the very first appearance of a root then put in moist soil. keep soil damp & mist 1-2 times a day....

Thank you for your reply. I use rooting hormone for most of my cuttings but with no luck the two times I tried it with a diffenbachia stem. Wish I could post a pic - the new plantlet is very healthy - about six inches tall. Do you mean use the r h on this one or a new one?
Beth

My diffenbachia plant is about 6 years old. It's the large leaf variety. In august I cut it back because it was leggy and put it back in the soil. The top portion of the 5 leaves were healthy, however, since then all of the leaves has turned yellow and died. There is one new leaf left and it has not opened and it is turning yellow. I cut it back again because the cutting got mushy. Can you help. I'm trying to save this plant,because my father started it for me and he is now deceased. Please help. thanks

Hi Yvette, welcome to Gardenweb! I would encourage you to start a new discussion in the house plant forum for your new question. Your question will be noticed by many more growers of Dief there. Has the original part from which you cut the top started to make a new top yet?