The Chelsea Chop

In the third week of this month you can 'Chelsea chop' your summer-flowering perennials to delay their flowering times. Sedums can be cut back by two thirds to provide lusher foliage, but at the expense of flower. 'Matrona' (the sturdiest pigeon-grey and pink sedum of all) responds well, as does 'Purple Emperor' - the best of the dark-leaved sedums. Reduce the front stems of phlox, heleniums and all yellow daisies, leaving the back two thirds alone. That way any drying foliage will be hidden by the later flowers at the front.