How can I trim my hydrangeas back?

Hi Joyce, it REALLY depends on the exact type of hydrangea that you have. Many of the common varieties do well getting cut ALL the way back to the ground every other year. This is what I do with my plant and it does really well. Any amount of cutting your do though needs to be done in very early spring or late fall.

Determine what type of hydrangea you have. Some bloom on new wood, some on old. See if these help.

https://www.finegardening.com/article/pruning-hydrangeas

https://www.finegardening.com/article/how-to-prune-hydrangeas

Here is a great video tutorial for you: https://www.youtube.com/watch?v=HunAJRIa-QU

Hello—Pruning hydrangea can be confusing. It’s because it depends on the variety of hydrangea. Knowing your hydrangea type is an important factor. Looking at your leaves and blossom will help ID the variety, please look at the references below for best practice recommendations. I hope this helps.

https://www.almanac.com/plant/hydrangeas

The timing of the pruning seem determines by the hydrangea variety according to this source.

Prune during the summer, just after the flowers fade:

Bigleaf or Florist Hydrangea (Hydrangea macrophylla)

Prune in late winter or early spring:

Hills-of-Snow or Sevenbark Hydrangea (H. arborescens ‘Grandiflora’),

Oakleaf Hydrangea (H. quercifolia)

Peegee Hydrangea (H. paniculata ‘Grandiflora’),

Tea of Heaven (H. serrata)

Prune as needed to control growth -

Climbing Hydrangea (H. anomala petiolaris)

https://www.thespruce.com/when-to-prune-hydrangeas-1403320

And another reference

http://www.finegardening.com/pruning-hydrangeas

The ones I see most often growing here in NC are the "Bigleaf" type. The flowers are usually blue because of the type of soil we have (acid from the pine trees, a soil azaleas also like) but they can be turned pink if the soil is treated to become more alkaline. If this is what you've got, pruning now will cut off the flower buds so you won't get blooms this year the same as pruning the common types of azaleas now would do. Pruning now likely won't kill the plant (unless it's a severe pruning) but it could elicit some growth that will get killed if we have a typical NC spring--- in my part of NC the last frost could be as late as April. So you could end up with bushes that look a bit unsightly. Ideally you should prune right after blooming.