The very same shade trees that we love in the Summer will drop their leaf litter in the Winter. While the presence of leaves and debris is pretty obvious on lawns, planters and walkways, not always realised that roofs are affected, too. Flat roofs, or corners and valleys of sloped roofs can harbor a surprising amount of debris just after one Winter season, including leaves, pine needles and cones, twigs and branches, palm fronds, squirrel nests, etc. There are a few reasons, why a prudent homeowner won't tolerate litter on the roof. When dry, it only takes a spark or a firecracker to ignite the leaves and then the whole roof. When wet, they act as a sponge: they hold water that promotes the growth of fungi and algae, and softens the asphalt shingles. These will all contribute to a shorter useful life of the roof. Some of the litter also ends up in the roof drainage system, the gutters and downspouts. These clogged gutters and downspouts tend to overflow, drip and dump water all over, but where thay are supposed to. Even with no trees close by, trash and toys (such as tennis balls)can end up on a roof and do as an effective job of clogging the gutter as leaves. Removing all form of debris from the roof should be part of the regular home maintenance routine. If you don't feel comfortable climbing a ladder and walking on the roof, please don't try to do this yourself. There are specialists you can call, or yard guys also may be interested in earning a few extra bucks doing this for you a couple times a year.