I do not even know what groundnuts are, but I know Jerusalem Artichokes (sunchokes) and have them 11 ft high each summer. We are in the piedmont portion of South Carolina with red clay soil. We plant the sunchokes in a raised bed (in the dirt, without sides) and we harvest all of the tubers during the fall, winter, spring (the tubers keep during the freezing weather in the ground). Invariably, there are many little pieces of tubers left after we harvest them "all." The second year we planted 16 -20 cut pieces of tuber, but found that the bed is already teeming with viable pieces of tuber, so the planting is not necessary. Jerusalem Artichokes are native (and invasive). Easy to grow, hard to get rid of.
They taste good raw. Crisp like a water chestnut. They can be kept in the refrigerator submerged in water for about 30 days. They can be kept in the ground until late spring, when they will all begin to grow new plants. They have little taste when roasted or boiled or steamed, think Irish potatoes, but take on the taste of anything they are cooked with or any spice added. The starch/carbohydrate of the JA is different (internet search will give the details; not my area). No fertilizer needed. No weeding. No maintenance. Lots of food. Indian gardening. Enjoy. Email
shiplaw@jhcooper.com if you want more info.