What sets the Endless Summer 1 gal. The Original Hydrangea Plant apart from other hydrangeas is its unique ability to bloom on both old and new wood. This means that this shrub can produce flowers continuously throughout the growing season, from late spring to fall. The blooms are large, mophead-like clusters of pink or blue flowers, depending on the soil PH. In acidic soils, flowers will be blue, while in alkaline soils, pink.