Minecraft wiki entry for Sweet_Berries, associated text: Sweet berry bushes past stage 1 slow down entities (except items) and damage mobs (though foxes are not affected either way). They deal 1 damage every 0.5 seconds to the player or other mobs. Entities that move through sweet berry bushes slow down to about 34.05% of their normal speed (similar to a cobweb, which slows down mobs to 15% of normal speed). This makes it impossible to jump a full block while inside the bush.