I apologize for this delayed reply to your gardening question. The spring rush has brought a deluge of questions and we are working hard to catch up!
You can plant that lavender into the garden if your soil is very well drained and the location is sunny. Lavender struggles and the heat and humidity of the South and prefers a semi arid climate for best growth of survival. The yellowing leaves could be due to soggy soil conditions were dry conditions for an extended period of time. Give it a good watering and then let it dry out quite a bit before watering again. Once rots get in from soggy conditions it's difficult to do much to save the plant.
Thanks for the question. Best wishes for a wonderful gardening season. Please stop in again soon!
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