Question
My 3 year old Victoria has produced one plum this year and is at present almost bare of leaves. It is planted in acidic soil that is 5.5ph although mulching etc may well have affected the balance since I planted the tree. Can you advise me, please as to what remedial action is necessary?

Answer
The pH should be a little higher than 5.5.  Somewhere around 6.0 is good. I would buy some agricultural limestone (calcium carbonate) and apply about one lb around the drip line of the tree. The product is a white powder and you can barely till it into the soil if you wish.  A light watering should help move it into the soil as well.  It will take about 6 months for the lime to take full effect, but this should fix most nutrient deficiency problems.  Good Luck.