Physocarpus opulifolius Diabolo - Ninebark

The Physocarpus opulifolius 'Diabolo', also known as Physocarpus or Common Ninebark, is a bushy and dense shrub, remarkable for its purple foliage that is so dark it appears almost black and then turns orange-red in autumn. It blooms throughout spring, producing clusters of dark red buds that open into small white flowers. It is also charming in winter when its bark peels.

The Physocarpus opulifolius belongs to the Rosaceae family and is native to the eastern United States, Quebec, and Manitoba. This shrub has a medium to fast growth rate and will reach a maximum height of 1.50m (5 ft) to 2m (7 ft) with a width of 1.50m (5 ft). The 'Diabolo' Common Ninebark is a deciduous and highly branching shrub with a dense habit, initially upright and then arching with age. It is remarkable for its almost black foliage in spring and summer, turning coppery orange and red in autumn. The leaves are lobed, deeply cut, and serrated, measuring from 3 to 8cm (1.2 - 3.1in). From spring to early summer, flat clusters of purple buds appear, opening into small, nectar-rich, white flowers with pinkish hues. These are followed by red fruits that are enjoyed by birds in autumn. The shrub remains decorative in winter, with its bark exfoliating in beige to reddish-brown plates.

Plant Physocarpus opulifolius 'Diabolo' in deep, humus-rich, moist soil that is neutral to acidic. It is sensitive to excessive limestone or acidity. It is important to avoid letting the soil dry out in summer and to spray the foliage during heatwaves. This shrub will thrive in partial shade or full sun, but the foliage colours will be more pronounced when planted in a sunny exposure. Thin out dense plants by severely cutting back some of the arching stems after flowering. This can promote the development of new flower buds later in summer. The Common Ninebark tends to produce many suckers, at the expense of the main stem; it can be beneficial to prune it to give it a denser appearance.

The 'Diabolo' Common Ninebark will work well planted in flower beds to create contrast with light-coloured foliage shrubs. It will be charming in a mixed hedge, alongside spireas (Spirea arguta, Spirea x billardii), arrowwood viburnums (Viburnum carlesii 'Chesapeake', Viburnum x bodnantense), compact winged euonymus (Euonymus alatus compactus), or Neillia (Neillia affinis) that it will illuminate. To complement its changing colours, Heucheras or Heucherellas can be planted at its base. It will also make an impact when planted in containers on a terrace or balcony.

The name Physocarpus opulifolia comes from the Greek word 'phusa', which means air bubble or vesicle, and 'karpos', which refers to the fruit, in reference to the shape of the fruit. Its specific name "opulifolius" is due to the resemblance of its foliage to that of the Viburnum opulus. Introduced to Europe around 1687, the many colourful cultivars created in recent years have led to its strong comeback in gardens.