Landscape architect Capability Brown was fond of placing deep purple copper beech trees among the greens of oak and willow; the variation of leaf colour slowed the viewer’s gaze and offered focal points within the landscape. I was reminded of the power of this simple trick in my own humbler herbaceous border. This spring I planted tubers of dahlia ‘Bishop of York’ for their pale yellow flowers, but, come summer, it was their dark foliage that made the most impact. The near-black leaves offered a foil for the flowers in front and behind, making the rudbeckia and scabious pop, but also breaking up the continuous greenery. My small border appeared a good deal larger.
If you have room, dark-leaved trees are hugely worthwhile as a backdrop. Against a fence or an open view, flowers can fade; against deep colour they become emboldened. Besides copper beech, which, for its scale, belongs in a park, favourites include black cherry plum (Prunus cerasifera ‘Nigra’), red Norway maple (Acer platanoides ‘Royal Red’) and the purple filbert hazel, Corylus maxima ‘Purpurea’.
For more modest spaces plenty of shrubs serve the same function: smoke bush (Cotinus), Japanese barberry (Berberis thunbergii), Physocarpus (‘Diabolo’ or ‘Lady in Red’, in particular) and, probably best of all, the dark cultivars of black elder (Sambucus nigra). A good planting combination is the slender yellow flower spikes of Ligularia przewalskii against a thick wall of black elder leaves.
On a herbaceous level, the low-growing black mondo grass Ophiopogon planiscapus ‘Nigrescens’, the many dark-leaf heucheras, and purple varieties of the succulent perennial Hylotelephium telephium. Here are a few hardy alternatives, most of which can be planted now for next year’s seasons.
Ajuga ‘Black Scallop’
Ajuga reptans is