Rachel's Garden Notes

I am working on a site that has river rock as their mulch. After removing two dead shrubs I have suggested replacing them with a hydrangea x paniculata 'limelight' and a hydrangea arborescens 'Annabelle'.
The concern I have is that the hydrangeas prefer a acid soil and the rocks provide too much alkaline along with heat. I will amend the soil with organic material and fertilizer for acidic plants, however, if given the choice I would much rather mulch them with a hardwood mulch. This would retain moisture and provide them with nutrients needed over the long run.
I use all sorts of rock as accents in my gardens to provide different textures and to stop run off, but given a choice would always lean to use of hardwood mulch for the plants.