Dividing involves splitting an established plant into several pieces, each of which has a section of the roots.
Watch our video guide to dividing hardy perennials.
When planting your new plants, help them get off to a flying start by working in well-rotted organic matter and fertiliser into the new area, then firm and water in well.
Take a look at some of the plants to propagate by dividing after flowering, below.
Lamiums are tough shade-loving perennials form mats of evergreen foliage, with flowers in summer. They make great ground-cover plants, so dig up and divide, then replant where cover is needed.
Tough and reliable, rudbeckias provide spectacular fountains of colour from summer and into autumn. By splitting the clumps, you can dot new colourful plants about the garden and rejuvenate the original plant.
The popularity of bergamot with bees and other pollinators is just one of the many reasons to propagate them. Divide these vigorous plants to improve their flowering performance and keep large clumps from spreading too far.
Stachys, or lambs' ears, will gradually spread to form large assemblages of silvery foliage, with purple-pink flowers. They're drought-tolerant and are brilliant wildlife-friendly ground-cover plants.
By diving up your hardy geraniums, you'll be rewarded with a bounty of vigorous new plants. If you find you have a surplus, simply pot up spare divisions and give to friends or family.
These versatile plants can be divided up once they've finished flowering, to be replanted under trees and shrubs or in containers. Ajuga is another fantastic evergreen ground-cover plant.
Video: How to divide asters
Spring divisionIf you've missed the boat for autumn division, don't worry. All the plants above can also be divided in spring, before they flower, giving them a near whole season to settle in and establish.
This special edition Year Planner 2023 contains advice for every month of the year, with tips for delicious harvests, plus, a sowing calendar is included for the best results all year round. Only £7.99.