Magnolia tree leaves make an ideal ingredient in compost. The green of the leaf has slight moisture and is nitrogen rich while the brown velvety underside is dry and carbon rich. With their thick, waxy and somewhat tough texture, magnolia leaves should be shredded, chipped or mowed over before being added to the compost pile. This will speed the breakdown of the leaves and therefore the creation of a rich friable compost.
Run your magnolia leaves through a chipper or shredder machine to cut the leaves down into small pieces roughly an inch or less in size. Alternatively, pile the leaves on the lawn and run over them several times with a lawn mower to shred them as much as possible.
Add shredded or chipped magnolia leaves to the compost pile in layers up to 2 inches thick.
Alternate with layers of nitrogen-rich green material -- such as weeds, grass clippings, and vegetable and fruit cuttings if you have more than 2 inches of magnolia leaves.
Add a pint or so of water over the freshly added compost pile ingredients to make them lightly moist and speed the microbial process.