Dactylicapnos scandens

This is a deciduous climbing perennial native to the Himalayas. It produces delicate, heart-shaped yellow flowers and fern-like foliage. It is hardy, fast growing and thrives in partial shade with moist, well-drained, humus-rich soil. Looks like it would have to be very happy to form a dense mound... new to me.

Tubifex, CC BY-SA 3.0, via Wikimedia Commons

peganum from Small Dole, England, CC BY-SA 2.0, via Wikimedia Commons