Answer: Probably the two most common sources for high soluble salts in a home garden would be overfertilization and runoff contaminated with winter de-icing salt. That could be leached by repeated heavy watering in quick succession to force it deeper into the soil, or possibly would leach naturally by heavy spring rains. You could try that and retest for the salts and see if it helps. I would not think masonry work would leave salts (I'm not a mason but offhand I can't think why it would), however fresh concrete can be very alkaline and could leach enough to raise the pH to where holly would not be happy. So you might check the pH as well if you have not already. When a plant dies repeatedly in one spot, I tend to suspect a soil problem such as poor drainage and/or a soil-based root disease. For example, perhaps the walk or a gutter drains close by that particular planting spot and makes the area extra wet. If it is a walk that you treat with salt in the winter, that could explain the salt as well. Without seeing the overall plant and its root system and symptoms, it is a bit difficult to make that type of diagnosis, but it might be something to discuss. I would recommend you consult with your local county extension and see if they have any additional ideas based on a review of the history of that spot in your plantings. In the meantime, I hope this helps.
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