White Flowering Hydrangea

Question

My hydrangea has tons of buds, but only a few petals open up on each bud cluster. Then they stop. They don’t fully open.

Answer 1

It is likely lacking a good phosphorus/nitrogen balance in the soil. Too much nitrogen or too little phosphorus will cause it to fail to bloom. This article will have some other suggestions as well:
https://www.gardeningknowhow.com/ornamental/shrubs/hydrangea/hydrangea-not-blooming.htm