Q. I have two African sumac tree and the past few weeks many of the leaves are dropping a lot each day and they are dry or yellow in color.  I am wondering if it is not getting enough water or if with the heat that may be its problem.  African sumac blooms during the winter and the flowers as well as dropping leaves can be very messy. A. First of all, African sumac is a messy tree. It can drop a lot of litter on the ground. The female trees can drop a lot of seed. Sparrows and mockingbirds love the fruit and will spread everywhere with sprouts given to neighbors.             If the tree is in rock landscape and on drip irrigation it might be a lack of water. You do not want to water daily but every 2 to 3 days in this heat at the most. Water with large volumes of water, less often.             If you do not think you are watering too often then I would run the hose out to it and let it get an extra 20 to 30 gallons under the canopy once a week now if it is an older, established tree.          It is also possible it could be aphids feeding on the leaves. Check them to see if leaves are sticky or shiny with honeydew from aphids. If so, spray with soap and water a few times a few days apart.             The soil will dry out faster if it is covered in rock mulch rather than wood mulch. Bare soil dries out the fastest. This tree perform better in desert landscapes if it has irrigated plants under its canopy.