Succulent plants that have just moved from a shady location to direct sunlight are likely to get sunburned. The sunburn on a succulent typically shows the worst damage on the top and sides 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 result in a whitish discoloration on the exposed areas. More severe burns will form a hard, brown scar, along with the plant, in areas that did not receive shade from spines or other stem parts.
Treatment
If you catch a sunburned succulent at the whitish discoloration stage, you can undo the damage by providing shade protection. However, if the plant reaches the brown scarring stage, the damage is permanent, and it will have to grow out of it over time. So again, prevention is the best defense against sunburn.
If you purchase a succulent plant that has been 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 gradually increase the time in 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