These were planted as part of a professional garden design; we did DIY install last Memorial Day. So I really want to stick with the color palette and habit of the two deceased varieties as much as possible, because they have to fit the overall plan.

The acanthus goes in a roomy space between a newly-planted Endless Summer hydrangea and a Spirea Magic carpet. There's still going be room for it for quite a while as these shrubs grow.

The Gallardia was in front of and sort of "underneath" a butterfly bush, although the area nonetheless gets tons of direct sunlight.

Any ideas? I'm just outside of Boston. I did ask the designer but she is super busy right now, and who knows when I'll hear back. Thanks!

And so I take it that your "butterfly bush" returned for you this spring?

If it is the coral-bell you will definitely know if it is dead or not. I've found 'Marmalade' to be a much longer lived coral-bell than most in the orange-y shades.

If it was a Gaillardia you may try a Coreopsis (tickseed). Lots of yellow varieties- 'Nana' is a nice dwarf one. The coppery 'Sienna Sunset' is also great if you needed something in that shade.

I don't grow acanthus either, but I would give it a bit more time. It depends largely on the species planted too; some are hardier than others. If it is dead, Baptisia (false indigo) may be a replacement option because it has "spiky" like flowers.

I'm sure others will have more ideas too ;-)
CMK

The butterfly bushes are fine--in fact, they never completely lost all their green leaves even in the most brutal part of winter.

Coreopsis might work.

Baptisia is beautiful but I wonder if it's too big? Acanthus sends up a narrower bunch of spikes almost like foxglove. Baptisia looks pretty bushy, and it's going to be next to a hydrangea bush.