Topinambur
Native Americans domesticated the wild perennial sunflower "Helianthus tuberosus" by selecting individuals with larger tubers. This crop plant (now called by the misleading name Jerusalem artichoke) was grown for its tubers and not for its seed. The perennial sunflowers being developed as an oilseed crop by modern plant breeders may have tubers, but they will probably not be harvested. Digging tubers is probably ecologically sustainable on a small scale. On a large scale, annually disturbing the soil makes it vulnerable to soil erosion. Avoiding annual tillage is one of the main motivations for developing perennial grain crops.