We have been living in our house for 4 years and the first year we had a beautiful bloom (cared for by previous owners) but since we moved in the blooms have been less than 25% of the first year. How/when do we cut mophead hydrangeas?
Your mop head hydrangeas (Hydrangea macrophylla) bloom in the spring on the branches from the prior year, called ‘old wood’. In other words, do not prune this variety of hydrangea in the spring, as you will effectively be cutting away the ready-to-go buds.
You may want to prune away the spent blossoms right after they have faded, mid-summer. As of today, mid-October, you may still carefully remove expired mop head blossom tips only — or leave them on for winter garden enjoyment. But do not prune back any existing branch material, as next spring’s buds are developing as we speak.
You don’t mention if you’ve actually been doing any pruning over the past 4 years, but wondering if some degree of spring pruning may have removed the other 75% of of the buds you’re missing. Also, as some day you may own a variety of hydrangea, please read HERE for an informative walk-through of the various types, and their optimum pruning seasons.