Agapanthus Peter Pan has been recently divided up in my garden

One of my worst failings as a gardener is not dividing congested clumps of perennials and bulbs often enough. It seems to be one of those jobs I just never get around to doing, always putting it off till 'next year'. There seems to be a tipping point when a lush and abundant clump stops flowering as well as it used to, due to overcrowding. Recently, I decided to divide up a border of mini Agapanthus 'Peter Pan', as I knew of someone who would like some for their new garden. I honestly could not believe the solid mass of roots on the plants when I dug them up. I felt so sorry for them. The border yielded literally hundreds of plants when split up. And they all started from about three plants I was given eight years ago!

Part of a congested clump of Agapanthus Peter Pan

Part of a congested clump of Agapanthus Peter Pan

Without regular division, there is too much competition for water and nutrients, and plants lose their vigour and start to decline. Also, over time, undivided clumps can become much larger than what we envisaged when we innocently planted a single specimen, and they take up too much space. Crowded clumps can also have problems with air circulation, which may lead to fungal diseases. The job of dividing is best tackled every two or three years. It is probably wise to keep a record of when the job is done, in a garden diary. It is amazing how quickly the years pass, and we realise we haven't done the task for say 10 years!

Hemerocallis Green Dragon: daylilies can be divided now

Hemerocallis Green Dragon: daylilies can be divided now

Now is a good time to divide summer-flowering clumping perennials - spring-blooming perennials are best done in autumn, so they can settle in over winter. The rejuvenated plants will establish quickly once spring gets into its stride. Apart from Agapanthus, suitable subjects include daylilies, Rudbeckia, bromeliads, perennial Aster, Hosta, perennial Phlox, Canna, Kniphofia, Liriope and Shasta daisies. Thick clumps of summer- and autumn-flowering bulbs and tubers can also be split up now, such as Dahlia and Zephyranthes. For bulbs such as Nerine, Lycoris and Amaryllis, wait till the foliage has died back in early summer, and only divide when they are very congested as they can sulk for a while after being split up. Spring-blooming bulbs can be split in late summer to early autumn whilst dormant. It's a good idea to note the positions of these bulbs in your garden now with a label, so you know where to dig when the time comes!

Dahlia Mt Noddy: dahlias can be split up now

Dahlia Mt Noddy: dahlias can be split up now

Once your clump is dug up, using a garden fork, it can be split into sections. Some plants divide up easily and can be pulled apart by hand, but others will need a knife, spade or even a saw to cut them up. It isn't always an easy job, which is probably why I procrastinate! In some cases, two garden forks, placed back to back, may be needed to lever tough clumps apart. Old, woody parts of the plant should be discarded. Damaged or dead leaves should be removed, and long roots trimmed. Cutting back some of the foliage of evergreen perennials will help reduce water loss after replanting.

Plant the divisions straightaway into soil that has been replenished with some compost, and water in well with a seaweed solution. Keep the moisture up until the plants start to actively grow again.

Phlox paniculata Graf Zeppelin: potted-up perennials and bulbs are great to give away

Phlox paniculata Graf Zeppelin: potted-up perennials and bulbs are great to give away

You will always have too many bits after the division of the clump and replanting of an area has been carried out! These extras can be potted up to give away to friends or for the sales table at your garden club. The best part about dividing plants is that someone else can benefit from the surplus thus produced! And you'll feel happy that you have given your plants a new lease of life.