Divide and Multiply
Have you ever visited a garden and been blown away by the perennial borders, with lots of one plant in big sweeping drifts, blocks or repeating clumps along the border?
By dividing the perennials you already have, you can start to create that big impact without spending a fortune. By repeating a plant through an area, you can start to create unity within the space, or a sense of rhythm along a pathway, for example.
Dividing perennials is not just about making yourself new plants; some perennials and grasses lose vigour if not rejuvenated through division every few years, or develop a donut-like form where the centre of the clump is dead. Division also keeps plants in check by reducing their size. Your new plants will also be exact clones of the original, unlike seedlings which will have natural variation.
There are two main ways to divide perennials. First, dig up the clump using a fork, bash off excessive soil while trying not to break off roots. For plants that develop a tough central core (eg. Veronicastrum), or a very tightly congested mass of roots, these are best cut through with an old serrated kitchen knife, a saw, or split through cleanly with a sharp spade. However, clumps that are a loser tangle of stems and roots (eg. hardy geraniums) can be split apart by pushing two garden forks through with their backs to each other, and then leaver the forks against each other to split the clump from within. If the fresh cuts bleed sap, leave somewhere sheltered to callus over before planting, to help prevent rot. Once divided, plant the divisions where you want them or pot them up as gifts, planting them to the same soil depth they grew at.
Many perennials can be divided at any time from autumn through to spring, but some are best divided in spring to avoid rotting-off in wet winter soil. Generally speaking, anything with thick chunky roots (eg. Agapanthus) can be divided any time during the dormant season, while plants with very thin fibrous roots (eg. ornamental grasses) are best divided in spring when the first signs of growth are visible. My guess is that thicker-rooted plants are more likely to retain enough energy stores to help them recover, whereas thinner-rooted plants are more likely to suffer energy loses from root breakage. Divisions made in autumn will often grow new roots before winter thanks to the warmth in the soil from summer, getting them off to a head start some spring. Spring divisions are best made once there are signs of new growth. Not only will this help you to see where the growing points are, but the oncoming rush of new growth with help the plant to overcome the disruption.
For more advice, why not follow the QR code and watch my how-to video?
Until next time, happy gardening!