Of all the plant parts we eat the most generally nutritious are probably the seeds. All the requirements for new lives are packaged inside and most seeds are thus very rich in nutrients as well as carbohydrates and or fats. World-wide we survive on seed crops, and their derivatives. Many are grown on an immense scale such as wheat, barley, rice, maize etc. In general these are hardly practical on a garden scale, it's not that we can't grow them but that they are awkward to harvest and process, and we need far greater quantities than most kitchen gardens can supply.