Cardamine trifolia

Cardamine trifolia is a charming perennial ground cover. It has dark green evergreen foliage that can resemble clover. In spring, the clump produces numerous clusters of white flowers. Unlike its dreaded cousin, hairy bittercress, this species grows slowly and steadily through its runners, but is not at all invasive. It will form a neat and bright little carpet under your trees and bushes in an understory situation, in shade or partial shade, in humus-rich soil. It also tolerates periods of drought once established.

Cardamine trifolia belongs to the Brassicaceae family (formerly known as the Cruciferae, due to their flowers with 4 petals arranged in a cross). Also known as Dentaria trifolia, it is mainly found in central Europe, from northern Italy to Hungary. It grows in light woods in medium mountain areas with moist, or even wet, soil. The name "cardamine" usually brings to mind the dreaded hairy bittercress (an annual that invades flower beds with its explosive fruits), but this species is really nothing like it. It has pleasant dark green evergreen foliage, with three slightly thick and shiny leaflets, whose shape is not unlike a clover leaf. It sometimes takes on beautiful purple hues with the cold. Between April and June, depending on the region, it produces abundant short clusters measuring 15cm (6in) which bear white flowers, typical of the family with their 4 petals. The clump slowly spreads through underground stolons, but never becomes invasive as its growth remains rather moderate. A well-established plant will reach a diameter of 30 to 40cm (12 to 16in). It is advisable to plan for several plants if you want to quickly fill a large space.

Very hardy (it can withstand -20°C (-4°F) without any problem), it appreciates a shady and cool environment, in humus-rich soil that is not too acidic. It can also tolerate sandy or even clayey soils (if they are sufficiently well-drained), as well as occasional drought. However, it will look prettier if the soil does not dry out too frequently. Maintenance of this plant is almost non-existent: it consists of removing (if desired) faded inflorescences at the end of spring. When the clump is large enough, it is easy to divide it. Sometimes, spontaneous seedlings appear under good conditions.

Cardamine trifolia provides excellent ground cover in a shady rockery, as well as at the base of deciduous trees and bushes, where its evergreen foliage provides year-round growth. Its white flowers will also bring brightness to a slightly dark corner. Combine it with Omphalodes 'Cherry Ingram', Epimedium 'Domino', or even Cyclamen coum and Asplenium trichomanes ferns.