Clumps to cleave
Summer-flowering perennials can be divided when the soil is still warm, writes David Overend.
You don’t have to be a genius in mathematics to know how to divide and multiply; and both procedures are also vitally important in the art of good gardening because they give you something for nothing. The real problem is timing – when to divide and when to leave well alone. Basically, there are two answers: autumn and spring – and gardeners are well and truly divided as to which is correct.
I prefer autumn, when the soil is still warm(ish) and summer-flowering perennials are ready to be lifted and divided to increase their numbers and, at the same time, reinvigorate them.
Get the fork, lift the targeted clump and then split it with the spade. As long as there’s a section of healthy root still attached, it should be fine and you have doubled, trebled or even quadrupled the number of plants without spending a penny.
Occasionally, it’s possible to get even more young, rooted plants from one parent. The drawback is that they will be smaller, but given the right growing conditions, they’ll bulk up to eventually become the next generation to bring a bit of colour to summer.
Give them a reasonable planting hole, enriched with organic matter, and, if necessary, water them in.
If the weather stays dry, keep watering to encourage new root growth and fresh top growth. Sometimes, it also pays to apply a mulch of organic material to help keep the ground that little bit warmer over winter.
With some perennials, it’s even more important to carry out this procedure in autumn – those established clumps of the likes of cone flowers will lose vigour after three or four years in the ground; the best way to bring them back to life is to lift and divide them.
Look for the tell-tale signs – when all the growth appears on the outer edges, the plant doesn’t bloom as well as it used to or the flowers are smaller than usual.
All these hint that the plant in question has roots too overcrowded to do their job properly.
Conversely, spring can, occasionally, be the best time to divide and conquer – late-summer and autumn bloomers are probably best left undisturbed until the following March or April when they start to produce new root growth.
Whatever your choice, don’t do it when the soil is sodden or frozen.