Had to look that up
and I was surprised we have a planting calendar right here on NGA
Looks like you have the same frost freeze date as I do Oct 10th but your winter is not as cold .
Your plants should do well out side , I would plant them by September 10th to give them time to get established .
The only time I have problem with lavender is when our winter is too wet so a dry sunny location would be best .
I often suggest to people to plant under the house overhang where not much rain hits if they are having trouble keeping lavender.
Having said all that I forgot to ask what type lavender you have?
Not all lavender is hardy (winter strong)
