In my USDA growing zone 5b it's not unusual to get late spring frosts so when I started my garden I planted for winter interest, then fall, then summer, and some spring as I can't stand the anticipation of spring and my first blooms destroyed by late frosts. I think my favorite fall/winter plants are the ornamental grasses. Their big plumes feed the birds and I get such a kick out of watching the birds teeter totter off the top of the plumes when feeding and snatching a few pieces to build their nests. In fall they add movement and sound with a gentle breeze. When winter comes they add structure and beauty from the glistening ice and snow which clings to them and sparkles on a sunny winter day.
