TREES & SHRUBS

How can I control rockery campanula that’s taken over? Q Why won’t acer put on growth?

ASome ‘rockery’ campanulas are really far too vigorous for a rock garden. These include C. poscharskyana (inset) and C. portenschlagiana (above), which look spectacular but spread by underground stems. These can creep under rocks, through and across smaller plants. If you’re organic, remove as much as you can with a trowel. Otherwise, spray the shoots with a weedkiller containing glyphosate. Use a ready-touse spray that can be accurately directed and don’t spray on a windy day.