Ivy is a much abused useful plant, particularly in conditions of dry shade where not much else will grow and cover significant areas. Maintenance is the key to keeping things civilised. Clipping the edges is important but even more important is keeping it out of trees. Once it gets up and away it tends to develop mature bushy growth that flowers and fruits too well; seedlings come up everywhere spread by birds who excrete the seeds after consuming the fleshy part of the berries. Keeping ivy under control, and in a juvenile state, prevents this happening.