Bouncing Bet (Saponaria officinalis) is a hardy spreading rhizomatous plant used for making soap. Add three root pieces to your laundry to create lotsa bubbles.
These areb sold as 8 inch long root pieces with plenty of dormant buds, bare root.
Photo: TeunSpaans, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons