Where are you? (general area)

On the coastal prairie, sw of Houston, I found it very difficult. Did fine as a winter annual, died in the humid heat of summer. Only way I could ever carry one through summer was to plant in a large unglazed pot, in a very sandy mixture. I mulched the top inch with crushed oyster shell.
--perfect drainage with an alkaline dry mulch.

Here in the area NW of San Antonio--it grows like a native. It's even grown commercially & there's an annual Lavender Fest in Blanco. 4" pots will become 3' shrubs in a year. I've got it in full sun & areas with a bit of filtered shade part of the day. The fernleafed types & dentatas have gotten killed by hard frost, but the plain old English type, Goodwin Creek, Grosso--have all done great.

So, my observation is it can handle heat & full sun well---DRY heat. It loathes humidity & poor drainage. I assumed it preferred alkalinity, too, since it does so well on this caliche garbage. Yet I read that in likes sandy acid soil--go figure.

If you're in a tricky place to grow it, start with one of the more robust types in an unglazed clay pot with lots of sand. Also, start it in fall, before summer heat & humidity--that's the killer for many lavenders in rainier humid areas, not cold. It's worth figuring out how to make it happy because it smells so wonderful & is so pretty.

I've got it as a foundation plant on the west side of my house. So far, so good.

Here in Kyle (between San Marcos and Buda), it grows well in full sun and caliche soil. It likes good drainage and prefers dry than soggy soil.

Omar