How to prune physocarpus opulifolius 'diabolo'

Immediately after flowering (June–July) for thinning; late winter for light shaping. Cut the oldest, woodiest canes down to ground level using loppers — this encourages vigorous new growth with the best foliage colour. Avoid cutting into old wood indiscriminately, as this weakens the shrub. A light late-winter trim shapes the canopy without removing flower buds.

Annually. 'Diabolo' ninebark flowers on the previous season's wood, so annual thinning after bloom keeps the plant shapely and productive. Remove one-third of the oldest, darkest stems at the base right after flowering. In late winter, you can also shorten any stems that spoil the overall shape.

Cut the oldest, woodiest canes down to ground level using loppers — this encourages vigorous new growth with the best foliage colour. Avoid cutting into old wood indiscriminately, as this weakens the shrub. A light late-winter trim shapes the canopy without removing flower buds.