Diervilla rivularis Troja Black

The Diervilla 'Troja Black' is a small bushy plant of interest from spring to autumn due to its changing foliage colour and long summer flowering. Slightly suckering, this close relative of weigelas and honeysuckles likes partial shade and blooms there for several weeks in summer, in clusters of light yellow to orange, enhanced by the purple-green and violet colours of its foliage. The diervilla adapts to all exposures, it can tolerate some drought and the root competition of large trees.

The Diervilla Troja Black is a horticultural selection derived from the Diervilla rivularis, a species native to the understory of the southern United States. This suckering bush of the Caprifoliaceae family has a bushy but spreading habit, with multiple stems originating from the base and the ability to cover the ground quite effectively. When mature, it reaches about 1m (3 ft 4 in) in all directions, with its lateral growth being quite easy to control by removing suckers or by planting other vigorous woodland plants alongside it. Its foliage is composed of oval, elongated, pointed leaves, slightly crinkled and shiny. The leaves are bronze-purple in spring, then partially turn purple-green in summer, before taking on a purple-violet hue in autumn. At the end of the season, the leaves dry up and fall off. Its summer flowering, appreciated by pollinating insects, takes place from July to August-September. Its light yellow flowers tinged with orange, arranged in clusters, will bloom on the previous year's branches, with a lovely purple colour. This diervilla offers abundant flowering, even in shaded areas and in the roots of trees where it particularly thrives. The highly contrasting colours of the foliage and flowers create a striking effect. The Diervilla rivularis is less resistant to drought than its cousin, the Diervilla x splendens, but it can tolerate occasional dry periods.

Low-maintenance, the Diervilla 'Troja Black' is adapted to all exposures and all types of soil, without excessive limestone and not too dry. Its small size is ideal for small gardens, enclosed spaces, or sloping soils. It retains and stabilises slopes thanks to its suckers (underground stems carrying roots). It is also an ideal choice for filling in an undergrowth. It will work very well in a rose garden or in combination with medium-sized perennials such as Japanese anemones or heucheras, and variegated foliage shrubs such as the Ivory Halo dogwood.