My guess is that wet soil not cold weather is dooming your Guara. Try growing this plant in a raised bed or rockery and do not prune or feed it in late summer, as you want to harden off the top growth. Do not use a mulch that traps moisture around the roots. Try using gravel or loose rock around the base of the plant instead. Give it one more try this winter. After that, perhaps you will have to accept that Gaura is a plant you will need to treat like an annual and replace your dead plant each spring. Keep growing, Marianne Binetti