A new and distinct Hydrangea cultivar named ‘；COF-HM1’； is disclosed, characterized by compact plants producing mop-head inflorescences with pink or blue flowers, depending upon the absence or presence of aluminum. Plants are well-suited to commercial applications, having a rapid production cycle. Rebloom potential is increased in plants of the new variety, which rebloom on both new growth and old wood. Plants of the new variety are cold hardy and bloom abundantly. The new variety is a Hydrangea, normally produced as an ornamental plant.
