The selected species belongs to the ....

Lateral roots of the primary root system or adventitious roots with adventitious buds. The roots with adventitious buds serve as storage organ and a connection between ramets. The lateral and adventitious roots decay within a few years causing fragmentation of the mother plant. Sprouting from adventitious buds on horizontal roots results in extensive vegetative spreading

[other examples: Ajuga genevensis, Convolvulus arvensis, Epilobium angustifolium].