A lawn waste collection system is designed to be removably coupled to a side-discharge, riding lawn mower in order to assist in the collection of leaves, The collection system includes an oversized collection bag for retaining a large quantity of lawn waste, an adapter kit for connecting the collection bag to the mower, and a shield coupled to the mower for supporting and protecting the collection bag. The adapter kit includes a multi-sectioned chute, which establishes a discharge communication path between the mower and the collection bag, and a frame for retaining the chute, collection bag, and shield. As a feature of the invention, the chute includes a primary section comprising a flexible outer layer, which universally connects to a wide variety of mower blade decks over the discharge exit port, and an initially planar, rigid inner layer affixed to the outer layer to provide structural reinforcement,