UNITED STATES—Now that leaves are falling, they need to be raked. Large leaves, like those of sycamore and fruitless mulberry, can shade out lawn, shallow ground cover or dense shrubbery. If shade is not a problem right away, mildew can be after only a bit of rain. If abundant enough, finely textured silk tree or jacaranda foliage that typically sifts harmlessly through shrubbery and most ground cover can accumulate and damage lawn, dichondra and the densest of ground cover. Walnut foliage has an herbicidal effect on sensitive annuals and some perennials.
Foliage is only beginning to fall. Cooling weather causes deciduous trees to shed more. Rain and wind bring the foliage down even faster. Even evergreen trees that naturally shed throughout the year will likely shed more through the upcoming wintry weather. Some trees start to defoliate early in autumn. Some hold their foliage until frost. Some trees that seem to be evergreen hold their foliage through winter, and then only drop their older foliage as it gets replaced by new foliage as winter ends.
Pavement and decks should be raked of leaves, not only to avoid staining, but also because rotting leaves can become dangerously slippery. Curbside gutters are too visible to get neglected for too long. However, heavy rain can quickly deliver to the cleanest of gutters a mess of fallen leaves as well as any other debris and litter that happens to be up the road. Strong wind can be filtered through hedges, leaving drifts of blowing leaves.
Leaves should also be cleared from roof gutters and downspouts, and may need to be cleared away again later in the season. More debris may need to be removed from awkward spots where it might accumulate, such as behind chimneys. Flat roofs may need to be raked.
There are a few exceptions to the need to rake fallen leaves. Where they get absorbed into coarse ground cover like Algerian ivy, falling leaves are generally not a problem. Pine needles and cypress foliage can be left if it happens to be useful for the natural suppression of weeds. Mature coast live oaks and valley oaks that are accustomed to a layer of their own fallen leaves over the surface of the soil actually want it to stay. For them, the foliar debris is a mulch that adds organic matter, insulates the soil, and retains moisture.
Highlight: red willow
It is almost never planted in home gardens, but the native red willow, Salix laevigata, has a sneaky way of getting where it wants to be. The minute seeds go wherever the wind blows them. Because it is a riparian tree, red willow prefers well watered spots. If not detected and pulled up in the first year, it can grow rather aggressively, and overwhelm more desirable plants, although the somewhat sparse canopy makes only moderate shade.
With a bit of grooming, red willow can be a handsomely asymmetrical tree, with upright branch structure. However, even the healthiest trees rarely get more than 30 feet tall or much more than forty years old. The leaves are a bit shorter and wider than those of the more familiar weeping willow, and do not color as well in autumn. There are actually a few other native willows that are also commonly known as red willow. Some are quite similar, while others are very different.