Lavender is a perennial, if it is lavender. It does pretty well here in Northern Nevada as long as it doesn't get too wet in winter and the variety is a hardy one.

It won't be easy to move mid-winter, because the soil is frozen. I'd dig a trench to hold the lavender in a well-drained area of the garden, then go dig the plants out, set them in the trench, fill with soil as best you can and then mulch over it with a mix of decomposed granite, sand and a bit of whatever soil you have to fill in the holes and crevices. Whatever you do, don't mulch with organic materials or the crowns could rot, and that would be bad. Add more egg-sized rocks if you want to hill up around the plants. Or pea gravel--that would work, too. Keep the crowns at the same level they were in the ground before.

Decomposed granite and sand aren't required--they are just what I usually have to hand this time of year because I also use them to grit the sidewalks when it's icy. Basically you want good drainage, light on the organic material.

Lisa