The calender says that it is now autumn. The weather does not necessarily agree. Some of the trees are dropping their leaves. However, the leaves are not falling because the weather is getting significantly cooler. The leaves got cooked during that weird heat wave a few weeks ago. If the weather can be this confusing here in our very mild climate, it must be really crazy everywhere else.
It is hard to make sense of what trees are dropping leaves in response to the earlier heat. Coast live oak, which normally tolerates heat quite well, was really annoyed by the heat in some areas. Cottonwood and other poplars are expressing their discomfort too, but that is to be expected from them. Sycamores, which are normally sensitive to weather anomalies, are not overly concerned.
All this means to us, the janitors of our trees, is that some of us might be raking leaves earlier than expected. These leaves will not be the nice colorful sort that we like to see in autumn. Those will come later. It is still too early to know how the weather will affect autumn color. All we know so far is that some trees will have less foliage for coloring. Sweetgums are hinting at a colorful autumn.
Leaves should be raked as they fall. However, because no one wants to clean the eave gutters any more than necessary, they can be cleaned only a few times, or maybe only once if trees shed efficiently. They are easiest to clean before the rain starts and the wet leaves start to decay. Unfortunately, most deciduous trees continue to drop their leaves well into the rainiest part of winter.
Lawns and shallow or dense groundcovers really do not like to be shaded by fallen leaves for too long. To perform through winter like we expect them to do here in our mild climate, they want as much sunlight as they can get while the days are shorter and the sun is lower on the horizon. Besides, fungal pathogens like mildew and rot, are more likely to proliferate under damp fallen foliage.
Finely textured leaves under low shrubbery and coarsely textured groundcover that ‘eats’ fallen leaves is a nice mulch, so does not need to be raked. If it can not be seen, and is not too abundant, it is probably not a problem. The exceptions are fallen leaves of roses, grapes, cane berries, deciduous fruit trees, and any plants that are susceptible to diseases that overwinter in fallen leaves.