I have been growing jade plants outside for several years now and they are doing well, except that I have noticed some of the plants' leaves are lighter than the others. This is the first time this has happened. The thing is, they need more humidity, but they are outside and I have them in a bed with plastic laid down and mulch on top. What I need is to figure out how I can make something or do something to try to make more humidity for them. I thought about getting the mulch wet and keeping it wet through the day when it is hot and possibly that might help, but I don't know. Do you have any ideas I can use to remedy this problem?
Most cactus and succulents are native to arid areas, and do not need as much humidity as thin leaved foliage plants. They also grow more slowly, and do not transpire as much water. Being succulent and storing water, cactus and succulents just don't require as much moisture.
Having said that, are the yellowing leaves the older leaves? If so, this is normal. If the whole plant is involved, they might need a dose of high nitrogen fertilizer. Or, in full sun, most plants have a tendency to 'yellow-up'. This can be corrected by providing a little shade from 11am until 5pm.