They say water blueberries with rainwater as to stop the PH of the soil being effected and to some extent the taste. To prevent the ericaceous compost from being neutralised just give them a feed during the summer months and top up the compost with an acidic mulch over Autumn and again in Spring.

However, tap water can effect the taste, making them bland but I have never had this problem and sometimes you have to use tap water.

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Best wishes
Andrewo
Harbinger of Rhubarb tales