Hydrangea Moonrock flowers open pure white like most paniculata types but then turn yellow-green at the tops, and will be an extremely light yellow in the fall. The chillier it gets the more vibrant the color. The flowers resemble a lava lamp or cone shape. The flower color on Hydrangea Moonrock is not affected by soil pH. Blooms on this super-hardy and easy-to-grow hydrangea are produced on new wood, which means that you will see flowers even after even the harshest winters. Beautiful for use as a cut (fresh or dried) flower.