It's that time of year again in St. Louis, Kirkwood, Clayton, Ballwin, and other surrounding communities with mature trees. Leaves are rapidly falling from deciduous trees so it's a good time to stop and think about options for handling the litter. Although a scattering of leaves won't harm the lawn, excessive cover prevents sunlight from reaching turfgrass plants.
Turf left in this state for an extended period will be unable to make the carbohydrates needed to carry it through the winter. There are options for dealing with the fallen leaves other than bagging them up and putting them out for the trash collector. Composting is a great way to handle the refuse. Compost can then be used in the vegetable garden and flowerbeds. If you do not compost, you can mow leaves with a mulching mower and let shredded leaves filter into the turf canopy. (A side-discharge mower also will work, but it won't shred the leaves as thoroughly.) This method will be most effective if you do it often enough that leaf litter doesn't become too thick. Mow while you can still see grass peeking through the leaves.
If you mow leaves and have a cool-season lawn, it makes sense to be on a fall nitrogen fertilization program and core-aerate in the fall (things you should be doing anyway in St. Louis). If you have a warm-season lawn, you can still use this technique but wait to fertilize and core-aerate until next late May or early June.