We expect our gardens to look great at this time of year, but they often run out of steam in August as plants start to look tired and wind down for the autumn. Kick against the inevitable by planting late develovers such as Penstemons, Heleniums, Dahlias, Crocosmias, Rudbeckia, Kniphofia, Agapanthus and Salvias, all colourful and vibrant and able to inject some freshness into your flagging gardens.