The mother species of this Bigleaf Hydrangea came from Japan. This cultivar with the large, hortensia (mophead) flower clusters has been replacing the old, very popular cultivar of 'Nikko Blue' because this new one can bloom on new wood and can be pruned at various times to rebloom the next year while the older cultivar can only bloom on old wood and be pruned right when the flowers lose their colour, otherwise won't bloom the next year. If the Bigleaf Hydrangea is not pruned sometimes, it becomes large and messy with dead stout stems among it. Either cultivar or any other similar cultivars are known as "the Hydrangea" in the Philadelphia, PA, region as it is so very abundantly planted there and around the Mid-Atlantic, offered from conventional nurseries to big box stores. Magically, this 'Endless Summer' is hardy to Zone 4, while the vast majority of this species cultivars were and are cold hardy only to Zone 6. Growing up in the 1950's onward, west of Chicago, IL, in Zone 5a, I only saw such a plant as a florist flowering plant, just like the Japanese Evergreen Azaleas. The hortensia or mophead flower cluster is a mutation that is composed of all the sterile showy florets that normally only ring the outside of the cluster; not having any of the tiny fertile florets that normally make up the rest of the inflorescence. Thus, it offers no pollen or nectar for pollinators. I much prefer the natural lacecap forms of any hydrangeas because their flat flower clusters, having both fertile and infertile florets, do supply pollinators and the flower clusters are not so heavy that they fall down. The flowers are blue in colour from the use of aluminium ions from acid soils from pH 5.0 to about pH 6.0; then they can be purple at a little higher pH, and then pink above pH of 6.5. The 'Endless Summer' Hydrangeas are mostly pink in the Chicago and upper Midwest due to most soils being around pH of 7.0.