Answer: Transplanting can sometimes send a plant into shock, especially if the weather is hot. Since you're an experienced gardener, you know that fast-draining soil is important for lavender plants so I expect you prepared the planting bed well prior to placing your new lavender in the ground. Watering well after planting helps settle the soil and then a thorough watering once each week should help the roots become established. I don't think your plant is a total loss, but it's likely to look puny until the roots become established. If you can provide some protection from hot afternoon sun, it will help. I've propped up pieces of cardboard to protect my newly transplanted perennial from sunshine and maybe you can do the same. Your lavender should overcome the stress and produce some healthy growth later this season. In the meantime, be careful not to overwater and be sure to provide some shelter from afternoon sun.
Best wishes with your garden!
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