I live in lower MI and purchased 3 Inv. Ruby hydrangea's - upon planting around a new patio built on a hillside I found that there is no soil where I had hoped to plant one of them. There is 2" to 3" of mulch and under that is what looks to be a limestone smaller rock base. I need to know if I pull the mulch back, and place soil on top of it, how deep the soil would need to be to support this type of hydrangea? I would then re mulch the area after the soil application. Is it worth the effort to put soit there in the first place? I cannot find how deep the roots will grow, nor if the lime stone base will affect growth / bloom. If anyone has suggestions / information I would really appreciate the input.
