Lavender is cold hardy and it overwinters in most places, and definitely will in Nashville. That is why LOWES and HD sell them , in the fall, in winter, in spring.

Lavender can grow quite big. Of course the first year will be about the size that you buy and plant. It needs slightly alkaline soil with dood drainage. You will need probably a 12" pot for it.

Though lavender could be put outside now, don't be tempted by other annuals or perennials that the box stores may be presenting. They are for sale because they've been told to begin selling the plants and because the staff doesn't know enough to steer people away from the tender varieties.

Sufficient sunlight and an exceptionally porous, fast-draining potting medium are the two most important factors for your lavender.