DOBBS FERRY, N.Y. — They have been burned, blown into piles, raked into bags and generally scorned by homeowners everywhere. Fall leaves — so pretty on the trees, such a nuisance when they hit the ground — have long been a thing to be discarded. But now some suburban towns are asking residents to do something radical: Leave the leaves alone.

In the past few years, lawn signs have sprouted in this Hudson River village and across Westchester County, proclaiming the benefits of mulching the leaves in place, rather than raking them up and taking them away. The technique involves mowing the leaves with special mulching blades, which shred them into tiny bits. That allows them to quickly decompose and naturally feed lawns and shrubs.

Officials are encouraging the practice for its cost savings: Westchester spends $3.5 million a year on private contractors who haul away leaves in tractor-trailers and bring them to commercial composting sites in places like Orange County, N.Y., and Connecticut. At the same time, environmental groups and horticulturalists are praising the practice’s sustainability, devising slogans like “Leave Leaves Alone” and “Love ’Em and Leave ’Em.”

Karen Engelmann, a novelist in Dobbs Ferry, used to rake up the leaves on her half-acre property, which is laced with old oak trees. She once had 120 bags of leaves lined up at her curb to be taken away by the village. “I wondered, ‘Where do these go?’ ” she recalled. “I thought it was odd that there wasn’t an alternative, that there wasn’t someone saying you might want to think about how the planet functions.”