first.. dahlia are a tuber.. which is NOT an annual .. though they can be grow as such ..

but when i used to grow them ... i would dig them.. and store them like a potato each year ... making them a tender perennial .... in zone 5 ...

there is a dahlia forum.. and i bet you will get better answers there.. though you never know where knowledge lurks in the GW forums.. lol ...

good luck

ken

You don't say where in zone 7 you live. It could be the south, and it could be the west coast. If you live in the south, I would say ask around locally where you live. With the exception of Bishop of Llandaff, I have never had much luck with Dahlias. They just don't seem to like our climate of heat, humidity, and hot nights. (It's entirely possible that it's just the gardener, but it might be the plant. Ask someone.)

I live in the SE part of Oklahoma.