Divide and rule!

David Perry demonstrates how to divide a clump of Miscanthus.

This week, I’m handing over to my partner in crime writing, Julia, to tell us about her latest trip to RHS garden Rosemoor where she received some seasonal advice.

It is such a treat to visit Rosemoor on a regular basis, as I am doing this year attending a series of talks, and to see the garden evolving with the seasons. Last week, I went on a garden talk entitled ‘What now? Spring’

The course notes said: ‘Let the RHS experts help you through the gardening year providing a whistle-stop tour of techniques, tips, tricks and advice on seasonal tasks so that you know what you could be doing when. Spring topics covered – dividing and planting herbaceous perennials, spring shrub pruning, cutting back of ornamental grasses, plus other topics of seasonal interest.’

This was exactly what I needed as I am never entirely sure what I should be doing when especially when it comes to pruning. Somehow, I had it firmly in my brain that I had to cut everything back in the Autumn… and was then surprised how many plants I manage to kill off every year! There really is no excuse for such ignorance as there are tutorials online and thousands of excellent gardening books but, somehow, it is always better to be shown how to do something first hand.

Our tutor at Rosemoor was Garden Manager, David Perry. Pruning is always a thorny topic, but within the first minute, David had explained two pruning terms that I had followed but did not know why – prune back to two buds and cut on an angle. Why two buds? If the top one gets frosted and dies, you still have the second one. Why cut on an angle? To provide a difficult surface for water, dust or parasites to settle on. Obvious, really!

The ‘bare bones’ at Rosemoor, beautiful in their own right.

Shrubs grown for their colourful stems or foliage, such as dogwood, need to be cut down in the spring to encourage new growth, known as coppicing. No wonder they hadn’t done well for me before, as I had chopped them off in November! He also demonstrated how to prune shrubs and roses into a ‘goblet’ shape, cutting out shoots that cross over, or were growing inward, to allow free airflow and a general rather lovely shape.

Buying plants can be expensive, so it is really useful be able to identify ones that can be divided to create more. All clump-forming herbaceous perennials, including ornamental grasses, can be divided and, when done regularly, helps ensure healthy plants that will continue to perform year after year. While perennials can be divided at almost any time if they are kept well-watered afterwards, David said it is best to do it when the plants aren’t in active growth. He demonstrated how to divide a substantial clump of Miscanthus using two garden forks back-to-back as levers to loosen and break the root mass into two sections. He made it look easy!

It was interesting to see the ‘bare bones’ of the garden at this time of year. The shape of espaliered and step-over fruit trees were art forms in themselves and it was also great to see the wooden supports staff were creating with coppiced sticks – so much more natural than bamboo poles!

How to divide perennials

Here are simple tips for dividing perennials from the RHS website:

  • Lift plants gently with a garden fork, working outwards from the crown’s centre to limit root damage. Shake off excess soil so that roots are clearly visible
  • Some plants, such as Ajuga (bugle), produce individual plantlets which can simply be teased out and replanted
  • Small, fibrous-rooted plants such as Heuchera, Hosta and Epimedium can be lifted and pulled apart gently. This should produce small clumps for replanting
  • Large, fibrous-rooted perennials, such as Hemerocallis (daylily), require two garden forks inserted into the crown back-to-back. Use these as levers to loosen and break the root mass into two sections. Further division can then take place
  • In some cases, a sharp knife, axe or lawn edging iron may be needed to cleave the clump in two
  • Plants with woody crowns (e.g. Helleborus) or fleshy roots (e.g. Delphinium) require cutting with a spade or knife. Aim to produce clumps containing three to five healthy shoots.

Top photo: Lovely pair of pottery chickens by Somerset artist George Hider.

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