Why are you adding ash? Are you trying to change the color of the bloom? The color of the bloom is determined by the ph of the soil, and you would have to first test the ph, then determine what color you wanted the bloom to be to know how much ash to add...BUT, add to much and you will kill your plant.
http://www.gardeners.com/Growing-Bl ... geas/hydrangealp%2Cdefault%2Cpg.html
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