Question
QUESTION: It is May 8th and my plum tree still is not showing buds!
Why? It has been quite a wet winter and spring so far and my sump pump deposits its rain water at its base. can that hurt my plum tree?

ANSWER: Sounds like too much water. Too much water can be as harmful as too little. Roots need water and oxygen to grow. As water is applied, it displaces oxygen in the soil pore spaces. Low oxygen levels result in root growth slowing, stopping or root dieback. If a tree is overwatered and remains saturated for long periods, or is growing in compacted or poorly drained soil, low oxygen levels often result in root dieback. The result is die back of the foliage.

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QUESTION: I am having my sump pump redirected away from my plum tree.
Will my plum tree come back after it has a chance to dry out?

Answer
If it is still alive it should leaf out. You can check to see if the tree is a live by starting near the end on a upper branch and scrape a small bit of bark off the branch and if the color under the bark is green the branch ids still alive. If it is brown then continue down the branch scarping at intervals until you find green or reach the trunk. If not green is found you can check other branches. OR just wait and see what happens. You may get some die back of branches if so after the tree leafs out you can prune the dead branches off.