No blooms on my hydrangea last summer - help!

https://www.gardeningknowhow.com/ornamental/shrubs/hydrangea/hydrangea-not-blooming.htm

Sara, I have the same problem. The first 4 years or so my blooms were so abundant. Then I had to trim the shrubs back because they got so large, and not one bloom since. I hope someone has an answer for both of us, because after 3 years without blooms, this is the year I dig them up and plant something else!

Often, the earlier you get it done after bloom, the quicker the shrub can recover, producing more and larger blooms next season. Don't prune these hydrangeas to the ground in late fall or early spring! Doing so removes all of next year's flower buds. ... When a Hydrangea gets old and woody, it can produce smaller blooms.

Did you trim them at the wrong time? Perhaps you removed the buds for the next year.

As a general rule (there are many different varieties with different pruning rules) the good old-faithful mophead hydrangeas should only be pruned immediately after the blooms are spent. They bloom on old wood, meaning this summer I will have blooms on the wood they pushed out last year after pruning. You don't say where you live but here in Western New York when I started having that problem my local nursery suggested feeding them with HollyTone now, early to mid-April. Since I've been doing that my blooms resurged and the blooms are huge! My hydrangeas came with the house so they are probably close to the 50 year old range. HollyTone is not harmful to pets either which is a bonus for me since my dog likes to supervise when I'm working in the garden :)

Check your soil ph levels. I know they need acid to turn a different color but they may be missing a certain nutrient that gives them the energy to bloom.