Berry Bushes are large green bushes with red berries on them that can be picked to for the berry food. Berries are a decent source of food (particularly when cooked) which is capable of comparing the to the cooked Morsel. They are great when found out in the field as you are collecting resources or exploring. Further the bush can be uprooted with a Shovel and replanted to create a reliable source of food closer to your base.
Maintaining a berry field requires you to use manure to revitalize the plants after replanting and after each set of five harvest. It takes roughly 3-5 days for the plant to bear fruit again once it has been picked. Since you need to replace 75 points of Hunger every day to survive and cookied berries provide 12.5, you'll need 6 groups of berries per day to survive. This requires a field of at least 30 berry bushes to ensure you have enough berries to survive. If you have a slightly larger field of berries, letting the berries rot can be a quick way to get fertilizer for your plants (at the expense of food).
While this is a great source of food during the summer, berry plants do not grow during the winter so a different source of food will have to be found to survive during the winter.