This is the first year I planted wave Petunias in my garden. I live next to Portland Oregon. What do I do with them in the fall when they stop flowering. Is the weather mild enough that if I cut them back will they come back next year or do I just rip them out and start from scratch next year? Help me.

petunias are annuals. so, they only live for one season. if they self seed, they may return. if not replant.

that is the trade off. annuals have more color + longer bloom time. perennials come back.