Peggy, we have the same scorching summer sun that you have here in central Florida. We also had our irrigation system capped off due to the valves freezing & bursting and leaking twice. Yes, it does freeze here in winter, and anything involved in irrigation repair can be pricey, hundreds of dollars pricey.
I had to work very, very hard last year to salvage so many plants that I had been given. I was determined to keep them alive in order to have a garden established before I get too old to do it. I did accomplish the feat and now have quite an extensive garden all around the yard, but we do have an HOA and we do still have lawn. I don't ever want to be a slave to lawn.
Doing all that intensive work last year I didn't protect my skin and developed so many pre-cancerous skin spots that had to be frozen. I hope you will protect yourself, no matter what you end up doing with the Lavender.
Here is what I can suggest, since I have tried every method of growing things here in this wicked heat. The biggest containers that are made of foam would work well and are light as a feather. Set up an individual irrigation system for each pot. They are easy to set up and you won't ever have to worry about if they are getting adequate water. My neighbors did this method for their window boxes, and it worked beautifully.
Place your containers on the side of the house that gets the morning sun only. That is my only saving grace for my tender plants, & herbs.
I think also that it would be best to try the Lavender on a small scale before you go all out because what if the lavender is not able to withstand that wicked heat, or does it bloom only once a year and would you just have a lawn of green plants except for spring/summer.
Don't get overwhelmed with gardening. Enjoy life and take it easy. Gardening is supposed to be one of life's
little pleasures for us. Bless you for wanting to have a yard full of Lavender. I used to want to go to France and see those beautiful Lavender fields.
