Every garden reaches a point where a border no longer looks quite the way it once did. The shrubs have become larger than expected. Perennials are competing for space. Plants that once looked perfectly balanced have gradually disappeared beneath more vigorous neighbours, while weeds seem to find opportunities wherever there's a gap. People often apologise when I arrive to look at a border like this. "It's got away from me." "I think we'll have to start again." Most of the tim