In case you're not sure, a tender perennial is a plant that is hardy in a warmer climate than what you're gardening in. Annuals differ in that they grow quickly from seed, blossom, set seed and die all within one growing season. Tender perennials, Pelargoniums for example, can easly be brought indoors for the winter. Now this may be more trouble than its worth--but if you have a treasured variety that is hard to find--this may be your only way of insuring you'll have it for next year. It's up to you.