My landscaper cut all of my hydrangeas and my butterfly bush to within 6 inches of the ground last fall without my knowing about it. Will they come back?

Butterfly bush most likely will. Hydrangeas I would think would but it depends on the type you have and how well they survived this weird winter. Give them time because they all come up later in the season. It will probably be next month before you start to see any new growth.

Yes, they should come back but if the list of pruned hydrangeas includes hydrangeas that produce flower buds in the July-September time period then you may not get flowers this year.

Hydrangea macrophylla and serratas produce blooms like mopheads or lacecaps. Rebloomer mopheads/calecaps will generate a late flush and may still manage to bloom from new growth produced this year. Oakleaf hydrangeas produce panicle-shaped blooms from flower buds that developed last year too so they would not bloom this year.

Annabelle-like hydrangeas (hydrangea arborescens) and Pee Gee-like hydrangeas (hydrangeas paniculatas) develop flower buds in late Spring to early summer so they would not be impacted by this type of pruning.

You may want to surround these bushes with short fences and also talk to the landscaper. The fences may -just maybe- give him/her a heads up that pruning should not be done.