Perennial border plants are mainly deciduous, dying back in winter and bursting into life again in spring.

Because they live for many years, they are best planted in a permanent place, but will need digging up every three years or so to be rejuvenated. Split them up (chop with a spade or tease apart with two garden forks back to back) and replant the outer pieces, well spaced apart. Discard the old centre.

Perennials sold as plugs or in containers can be planted at any time if the soil is neither frozen nor waterlogged. However, autumn is the best time, when the soil is warm and there is no danger of drought, so you don't have to water. If you buy bare-rooted plants, they will have been dug up from the ground and should be planted immediately, so make sure you are ready before delivery. Large perennial plants are good value as you can split them up before planting to cover a larger area of ground.