Creeping Jenny

Lysimachia nummularia runs flat along the ground on thin stems set with small round leaves, rooting as it goes, and in a season it will knit into a continuous mat 50 millimetres deep. The golden-leaved form is the one usually specified, and it holds a strong lime-yellow all season.
It is a moisture plant, at its best at a pond edge, along a rill or spilling over the lip of a raised planter, and it will not carry a dry exposed site.
Creeping Jenny is the mat-forming ground cover to specify where the site is damp and the finished level needs to read as a single flat green plane.