I have alchemilla (Lady's mantle) at the base of my hydrangea, which provides early foliage and bloom before the hydrangea really takes off. When the Lady's mantle flops over is about when the hydrangea is really bulking up (early August). I also have the small groundcover comfrey in back of the hydrangea, which tolerates the fairly dense shade as the hydrangea takes off. Symphytum grandiflorum. Sorry, I'm not as versed as others to make links to the plants in the database, but both are there. And, finally, I do also allow some Lamium to grow under the hydrangea, although some folks consider this plant to be a pest. This is all under a common hydrangea macrophylla, not your particular variety, which is very pretty with the variegation.
