Plant this compact hydrangea into a border along a low fence or edging a sidewalk, and it'll reward you with large double mophead blooms that change colors as they mature. They will start out light green in spring, and by late summer they will mature to violet or pink. Be sure to check your soil's pH level if you're looking for a specific bloom color. About 5.2-5.5 produces violet flowers, about 6.0-6.2 produces pink flowers. This dwarf shrub also draws attention as a container accent, and attracts butterflies. Be sure to check your soil's pH level if you're looking for a specific bloom color. About 5.2-5.5 produces blue flowers, about 6.0-6.2 produces pink flowers. Hydrangea macrophylla 'REI05'