Answer: According to the experts at Raintree Nursery, plum trees like soil that's slightly acidic. The mulch you used will help enrich the soil, prevent excessive evaporation of soil moisture, and keep the soil cooler in the hot summer months. A good rule of thumb is to apply a 3"-6" layer of organic mulch in an area beginning about 6" away from the trunk of the tree, extending to the branch tips of the tree. If you place mulch material up against the trunk of a tree, it might hold too much moisture against the bark and cause some problems with rot. Keep it a few inches away for best results.
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