GARDENING - Divide and rule the herbaceous border

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Telegraph

Divide and rule the herbaceous border (Filed: 27/10/2001)

Increase your plant stocks now, using our step-by-step guide by Carol Klein

DIVISION is the time-honoured means of producing new perennials. It makes fewer plants than sowing seeds or propagating from root cuttings, but it is straightforward and foolproof.

A few herbaceous plants cannot be divided, but they are the exception. Eryngiums, which have a single tap root, or cranesbills with one solid crown, are typical examples for which division would mean certain death.

As long as each division has its own roots and new shoots or the potential to make them in the form of resting buds, it has all it needs to make a new plant. For most ordinary border plants, division is the most reliable method of increasing stock.

As well as benefiting the garden, it is great therapy for plants. Although such herbaceous plants are called perennials, they often need help to stay that way. Most develop woody crowns which lead to reduced performance.

In traditional herbaceous borders, plants would be cleared out every two or three years, divided and replanted, simply to rejuvenate them.

Autumn is the perfect time for division and replanting. Most plants have made good root growth and new shoots for next year. The exceptions are the really late flowerers, such as Michaelmas daisies, which need the winter and spring to gather their energies and produce new basal growth. They are easily increased in April by "Irishman's cuttings" - single shoots with their own roots, pulled from the edge of the main clump and planted immediately.

Fibrous-rooted plants, such as primulas, can be lifted and gently teased apart. Hands are best. Discard the old thick roots, retaining only new rosettes with fresh young roots. Before replanting, trim roots to about 4in (10cm) with a sharp knife. This encourages fine fibrous feeding roots. I don't like cutting back the roots of members of the lily family, such as kniphofias, nor those of ranunculacae, the buttercups, both of which, if cut, are prone to rot in my wet soil. I prefer to give them a deeper planting hole. Never fold roots when replanting - the plants may die.

Refresh soil with good organic matter and avoid returning plants to the same place to avoid build up of disease.

All fibrous-rooted subjects can be treated in similar fashion. It often pays to wash the roots so you can see what you are doing. Clumps are best pulled apart by hand but, occasionally, an old carving knife may be needed.

Don't be afraid to trim back top growth. You will be able to see what you're doing more clearly and the plant will find it easier to re-establish without the added burden of maintaining old leaves.

Tougher plants, such as day-lilies, which form hearty clumps but none the less have fibrous crowns, may require more extreme methods. Having lifted the clump, plunge two garden forks back to back vertically into its centre. Push the handles together and prise the crown of the plant apart. The process can be repeated to more manageable chunks.

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-- Anonymous, October 29, 2001


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