With what seems to be an endless array of Hydrangea paniculata cultivars entering the market, July has turned the garden into a snow white scene. The Asian Hydrangea paniculata was first published as a new species in 1829, but was not grown in the Americas until Arnold Arboretum director, Charles Sargent brought back seed from an 1892 expedition to Japan. That original plant, now, 131 years old, measures 16′ tall x 25′ wide. I’m not saying you need to plan for your Hydrangea paniculata to reach 131 years old, but the average of a house in the US is 46 years, so logic says we should at least plant for a 50 year mature size.
Below is our clump of Hydrangea ‘Rensun’, which is marketed under a completely different name, Strawberry Sundae. The introducers of this lovely clone tout this as maturing at 5′ tall x 4′ wide, but our 6 year old specimen is already 7′ tall x 11′ wide. Based on that growth rate and the mature size of the species, I’d expect it to reach 14′ wide x 22′ wide in 50 years. It’s truly fascinating why it’s so difficult to for plant breeders to get more accurate measurements before these plants are introduced to market. One can only imagine the maintenance problems caused when you locate plants based on the size given on the plant tag, only to have the plant get 2-4 times as large as your space allows.