Juliet Sargeant, award-winning garden designer

AGAPANTHUS

‘Agapanthus are one of the few rounded flower forms, like alliums, and are available in a variety of sizes and flowering times. The only downside is that they are not all hardy, so if in doubt, cover them with mulch in winter.’

CANNA

‘These are invaluable for late summer pizzazz and before they flower, their leaves are equally eye-catching. Cannas are not hardy, though, so need protection in winter.’

PENSTEMON

‘Penstemons are some of the longest flowering and most reliable perennials. There is a wide range of colours. Wait until after the frosts to cut them back to ground level.’