Answer: Morning sun should be fine for this plant. It does need an evenly moist soil and a sign of moisture stress would be curling leaves. Check with your finger and make sure the soil is at leaset as damp as a wrung out sponge. When you water, water slowly and deeply so it soaks down deep and encourages deep roots where the soil stays naturally moister longer. (This is better than a daily light watering or sprinkling which encourages shallow roots.) After you water, wait a few hours and then dig down to see how far the water went; it can be surprising. To know if you need to water, dig into the soil with your finger. If it is still damp, don't water yet. Using several inches of organic mulch over the root area can help keep the soil cooler and moister as well.
One other possibility is that the plant has not rooted out into the surrounding soil so it is stressed even though the soil is moist enough. If it had encircling roots at planting time, for example, the roots would stay growing in a circle and strangle the plant. You can check for this by digging down gently. If the roots are still in the original mass you may have to lift the plant, cut the roots and reset it.
It is also possible there is a pest or disease problem, so if neither of the above seem to apply you might want to consult with your professional nursery staff for help in troubleshooting. Good luck with your clethra, this is a great plant!
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