Autumn is a great time to divide herbaceous perennials – not only does this keep them looking their best by retaining their health and vigor, it also gives you lots of new plants to use around the garden and to give away to fellow gardening friends.
When it comes to dividing, it’s important to know which plants should be done now and which should be left until the Spring. Generally, the majority of plants can be divided now and over the next six weeks or so – that includes likes of Salvia, Geranium, Astilbe and Sedum. The only exception is tender late-flowering perennials, such as Heleniums and Echinacea, as well as ornamental grasses – it is best to leave these till next year to give them the best chance of surviving the Winter.
Below we’ve included our step-by-step guide to get you started with dividing. Follow this and your plants will be looking good in no time!
1. Don’t divide a plant too soon. Plants generally require 2-3 years of healthy growth before they are at a suitable stage for division.
2. Using a large fork or spade, tease the whole plant root out of the soil so that you have one large clump.
3. Trim back any old top growth which is withering or looks dead – this will help the plant to re-establish itself when you replant it in smaller sections. Otherwise your new plants will channel energy into maintaining old growth. At the same time, trim off any old roots which will not re-establish easily.
4. Place the clump onto an old piece of tarpaulin and plunge two garden forks back to back vertically into its middle. Push the handles together and gradually prise the crown of the plant apart – repeat as necessary until you have a few divisions, approximately 20cm squared each. Many plants have a root ball which is much too dense for this or a very solid mass from which the shoots appear - if this is the case, use a sharp spade to slice through the base of the plant. As the segments get smaller, you may want to switch to a sharp knife to divide them.
5. Remove any diseased material which is showing signs of weakness – whether that’s spots on the leaves, mildew or rust. Don’t put the diseased material in the compost heap – try to burn or dispose of it in the bin if you can to prevent further spread of diseased materials.
6. Now you have your new plants, select where in the garden you would like to replant them. Dig in plenty of organic matter – ideally garden compost or leaf mould but any compost will help– and replant. If you're not sure where you want to use them, or you want to share them with your friends, pot up into 2 litre pots to allow them to establish a new root system. Keep them well-watered and feed in early spring.
Most importantly of all – have fun and enjoy the creativity of finding homes for your new plants!