Are sweet peas annual? I winter-sowed some and planted them out last Spring. They grew foliage but no flowers. This year they came back, which surprised me, and grew even bigger and finally flowered. How come? I guess this is it, and they won't come back next year? So I should start more from seed if I want them next year (or the year after, as the case may be.) Can someone please explain this to me? Thanks.