"The concept that foods can be eaten only in appropriate quantities is taken so much for granted that, to my knowledge, it has never been given a name in the medical literature. I call it the maximum caloric proportion (MCP). Some foods have a very high MCP, such as milk, meat, and potatoes. They are easily digested and contain few antinutrients or toxins, thus they are suitable as dietary staples. Others, such as cabbage, rhubarb, and raspberries, cannot serve as staple foods and are only suitable to supply small portions of the diet. As one travels north, there tends to be fewer plants with a high MCP; this is why hunter-gatherers from northern latitudes ate meat for the great majority of their calories." Samuel Thayer
I eat berries and other edibles sometimes but its really more for fun and the pleasure of eating fresh wild blueberrys ect. But there is no way you can travel and gather any real portion of your food. Fishing may be the only exception. the only plants that can provide any real amount of calories is root vegetables. And as always it really depends on where and when your hiking. Most wild root vegetables are pretty small and you need to gather a decent amount of them. Sometimes they need to be boiled or prepared in some way before they can be eaten. Remember too, they need to be in season. Greens and berries might be good for you but they are side dishes eaten for variety more than any need.