After peak hydrangea season is long in the rear view mirror, the Japanese/Taiwanese Hydrangea involucrata erupts in flower. For us, that means August and September in NC. The main clone on the market (pictured below) is Hydrangea involucrata ‘Wim Rutten’, from Dutch plant breeder, Catherine Rutten. Our garden specimen is now just over six years old, and has grown to 3′ tall x 6′ wide. We grow this lace cap hydrangea in part sun/light shade. Hardiness 6b-9a, at least.
Could this be container grown in 5b? I fear If I tried in ground with mulch and burlap the buds might still freeze. But this looks beautiful.
It could easily be grown in a container if you keep the container around freezing in the winter, but would not survive in a container outdoors in Zone 5b, since the roots would freeze.