Should I divide my herbaceous perennials now or in spring?

Mandy Morrison, by email

Stefan says: This is a question I’m asked with regularity around this time of year. Just last week, Carol Klein’s article in GN was full of the joys of dividing herbaceous perennials to make more free plants. Many gardeners wonder if they’ve missed the boat by doing nothing in the autumn and/or if they’ll do any harm by trying to make amends later. The answer, like so much of gardening, is that in many cases it doesn’t matter very much and you can get away with whatever’s convenient for you.

However, hardiness does come into it, as does the part of the country in which you live. Some plants, of course, are quite tough enough to withstand autumn division without any harm at all. Michaelmas daisies and similar trusty border perennials won’t bat an eyelid. But others, including peonies and similar species with large and fleshy roots, are much better divided just as growth is beginning again in spring.

There’s something of a myth about division in spring causing you to lose a year’s flowering. This really is a myth and, provided you do the job with the minimum of disturbance and don’t wait until growth is too far under way, you’ll notice little effect. Whenever you do it, be considerate to your plants. Too often I see gardeners digging up a huge clump with a spade, chopping it in half and then replanting the two pieces. Unless a plant is very hard and woody (which suggests it’s been left for too long before being divided anyway), I prefer to do the whole operation with a fork and with my hands.

A fork will cause less harm to fibrous roots and the clump, once uprooted, shouldn’t simply be hacked into two halves but pulled into several pieces, those moribund bits from the middle being discarded and only the new, vigorous growth from the periphery replanted.

Don’t forget to prepare the planting position with compost and a light dressing of bone meal, just as you would with any new plant.