Place a plastic sheet on the ground under the mulberry tree.
Grasp the lowest branches of the tree and gently shake them. The fully ripened mulberries will fall from the tree onto the plastic sheet below. Unripened berries remain on the tree.
Pour the contents of the plastic sheet into a large bucket and fill the bucket with water.
Pick out with your hands any leaves or twigs that float to the surface.
Pour off the water, leaving behind the ripened, washed mulberries at the bottom of the bucket. Use the berries within two days.