Answer: Sedums should do well in a well drained site with full sun or afternoon sun. I think your new sedums are still just becoming established and rooted, especially if they were just recently planted. That they recover in the evening means they are basically losing moisture in the heat of midday faster than they can take it up through their roots. Since they recover once it cools off they should be okay once their rooting is more developed. Plants that have been pushed in a greenhouse or overfertilized are more prone to this, as are plants that are going through transplant shock, or those that were rootbound at planting or have suffered some time of root damage. There are several points that can contribute to this type of situation. I hope at planting any encircling or densely matted roots were sliced or unwound and directed outward into the surrounding soil. The planting hole should be generously wide and about as deep as the rootball, also to encourage the plant to root over a wider area. The plant should be set at the same depth as it grew in the container, no deeper. YOu should use a layer of organic mulch several inches thick over the root area, but do not allow it to touch the stems. Finally, the soil should be evenly moist but not saturated or sopping wet. To know if you need to water, dig into the soil with your finger. If it is still damp, don't water yet. Another option you could consider is, if the plants seemed overly developed when you purchased them compared to other sedums growing in the ground in your area, you could trim them back by about half. This would reduce pressure on the root system. (You can probably root the resulting tip cuttings.) If your plants do not seem a bit better in a week or so you may want to check back with your retailer for help in troubleshooting. I hope this helps.
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