At this time of year, just when plants are entering their dormant phase, I always look at the overcrowded clumps of perennials dying down and decide what I need to lift and divide next year.

Dividing plants involves digging them up, splitting them into pieces which each have roots and growth shoots or buds, and then replanting them. The method stops many herbaceous plants becoming overcrowded, untidy and invasive.

Many perennials, including delphiniums, heuchera, hostas, anemones, phlox and cranesbill geraniums, benefit from regular division to maintain health and vigour, and require no special conditions when new, divided sections are replanted.

Other plants benefit from division every three to four years although some, like asters, are best divided annually. A few, including red hot pokers and peonies, hate being moved, so only lift and divide them if you want to propagate them.

The best time to divide plants is autumn, when they are dormant, and spring, when they are just starting into growth. Grasses including bamboos should be divided in early spring, while perennials which flower in spring and early summer should be divided as soon as they have finished flowering.

There are various ways to divide plants. Those with tough roots which are difficult to prise apart, such as hostas, are better off being dug up and then cut into thick slices with a knife like you’d a cake, making sure good roots are present in each slice.

Other plants can be lifted carefully with a garden fork, working away from the crown centre to limit root damage, then split into two portions across, each with some roots, shoots or buds. Larger pieces with more roots are likely to flowers sooner than small ones, which may take a year to recover.

If you are digging up a clump, remove the centre portion, retaining the younger outer parts for replanting. If any sections are short of roots, trim the leaves to reduce moisture loss.

Plants with fleshy roots, such as delphiniums should be cut with a spade or knife. Divided clumps should ideally contain around three to five shoots.

When replanting, add compost or well-rotted manure to the planting hole on a new site, or a balanced fertiliser if you are replanting the divisions into the same hole. They should be replanted at the same depth in flowering positions and watered in well.

Alternatively, pot up divisions while you decide where you want your new plants to grow, overwintering them in a cold frame.

Before long, you’ll have an array of new plants – which won’t have cost you a penny.