Succulent plants just moved from a shady location to direct sunlight are likely to get sunburned. The sunburn on a succulent shows the worst damage at the top and side facing the sun. Ridges are more likely to burn than valleys along the plant stem. Sometimes, cacti have wide ribs and little spine protection, and sunburn will occur between the ribs. A light burn will be a whitish discoloring on the exposed areas. More severe burns will become a hard brown scar along with the plant in whatever areas did not get shaded by spines or other stem parts.
Treatment
If you catch a sunburned succulent at the whitish-discoloring stage, you can undo the damage by getting shade protection. However, if the plant gets to the brown scaring stage, the damage is permanent, and it will have to grow out of it in time. So again, prevention is the best defense against sunburn.
If you purchase a succulent plant sitting inside a store for some time, you will gradually need to move it into full sun. Do this by giving it full sun for a short period each day and then regularly increasing the time in the full sun over a couple of weeks. Keep in mind that some species do not ever want full sun all day. Therefore, the stronger the sun where you live, the more careful you have to be to keep your succulents sunburn-free.
Source: succulentguide.com
Links
- Succupedia: Browse succulents by Scientific Name, Common Name, Genus, Family, USDA Hardiness Zone, Origin, or cacti by Genus