The patch of leaves is Mistletoe, a plant that is an obligate hemi-parasite. Obligate means that it must grow on another plant, and hemi-parasite means that it uses photosynthesis to produce some of its nutrients, while getting water and others from the host. Although it is a parasite, it actually helps many trees by attracting birds that spread the tree's seeds. They also spread the Mistletoe seeds, growing new Mistletoe plants.