We have 2 hibiscus plants next to our front entrance. We planted them last spring and the grew to be really nice size, about 5 feet tall and flowered up to first frost. This spring it is showing no life as of yet and we are wondering if they survived the winter. We live in the Midlands of South Carolina and we generally have mild winters but it did get below freezing several times.this winter. Haven't tried to prune them yet. Is there any way to tell if they are still alive or do we have to replace them?