creeping Jenny

It is a vigorous, prostrate, evergreen perennial growing to 5 cm (2 in) in height and spreading rapidly and indefinitely by stem-rooting. It has rounded leaves arranged in opposite pairs, and cup-shaped yellow flowers 2 cm in diameter, in summer. It is particularly associated with damp or even wet areas, though in cultivation it will tolerate drier conditions. It is hardy, surviving lows of −15 °C (5 °F) (RHS H5).

It is native to Europe, but has been introduced to North America, where it is considered an invasive species in some areas. It aggressively spreads in favorable conditions, such as low wet ground or near ponds. It can be weeded by hand, if all stems and stem fragments are removed, to prevent the stems from rooting and regrowing.

The cultivar 'Aurea' (golden creeping Jenny) has yellow leaves, and is somewhat less aggressive than the undomesticated species. It is cultivated as an ornamental plant, for groundcover where the range of its growth can be limited. It is also suitable as a bog garden or aquatic marginal plant. It has gained the Royal Horticultural Society's Award of Garden Merit.

The Latin specific epithet nummularia means "like a coin", referring to the shape of the leaves; hence the common names, such as "moneywort", which also references coins.