Butterfly Bush

Your flowering shrub is likely a butterfly bush, a sub shrub in your area and can die back to the ground when in areas with cold winters. This by itself is not a problem because many people cut it back to the ground in spring. There are two reasons why they might not make it through the winter. One, the soil might be getting too cold. Provide winter protection such as a mound of chopped leaves around the base of each plant. They should be hardy in your area and such protection shouldn’t be necessary, but perhaps it is windy there. Two, the soil could be too wet, causing the roots to rot. It is very difficult to correct drainage problems after plants are in the ground. Applying an organic mulch around each plant at least as wide as the shrub, and maybe wider, will eventually improve drainage as the mulch rots each year and adds organic matter to the soil. You may want to consult a horticulturist at a local garden center or botanic garden in case there is a local problem with these shrubs that we don’t know about. It is a lovely butterfly and bird magnet.