I have several 'Heatwave Glimmer' salvias in my garden. They are wonderful plants, a gregii x microphylla cross, soft white, blooming most of the year, nice shrubby form, and disease free. I really like them.

The problem? They are just too big for my garden plan. They are supposed to be compact, but in my garden they grow about 3 feet high and 4 feet wide. I need a similar plant but it really has to be smaller. I'd like them to be about half that size, say 18" high and up to 24" wide. The replacement plant would not need to bloom all year long. I don't really much care about winter bloom and I have a lot else blooming during the spring, so summer and fall are my goals. The new plants don't have to be salvias, though I do like salvias. I definitely want white. I have considered Salvia nemerosa, but some I tried a number of years ago flopped open the middle which I do not like. I know they don't all do that do, as 'Caradonna' is fine, as is a handsome blue I planted years ago and still grow.

Any ideas? I should mention this garden bed is in full sun and gets regular garden water.