Root Division for border plants

DIVIDE AND MULTIPLY
If you are the proud owner of an established garden, you may be disappointed to see your borders looking a little tired, sprawling or straggly. Root division is an easy way to rejuvenate your plants and increase your stock. What’s more, it costs nothing and requires minimal equipment.
Ideal candidates
After about four years, many varieties begin to die from the inside (the oldest part of the plant). As well as leaving unsightly gaps in the border, old and tired plants can be a magnet for pests and disease, which will then spread throughout the garden. Division is a method of propagation in which the dead and weak parts of the plant are removed and the new shoots re-planted. Many familiar perennials such as hostas, aquilegia, delphinium and rudbeckia are suitable for division. In fact, most clump-forming plants can be easily divided to produce more plants.
Refresh and revive
The ideal time to get started is autumn or early spring – this allows the plants to recover while the soil is moderately warm and before the growing season begins. Large well-rooted clumps are best removed from the border with a fork or spade, and split apart. It may seem brutal, but when freed from tangle of roots the newly-divided plants will really begin to flourish. A large mat of tangled roots can usually be split into at least four new plants without compromising the essential root-structure. Simply transplant the divisions, discarding any obviously dead or diseased portions. Some varieties, such as hostas, develop thick gnarled roots after a few years’ growth, making them impossible to split with a spade or trowel. In this case a strong, serrated kitchen knife is invaluable for slicing through the tough root ball. Less vigorous perennials need not be dug out in this way, and it may be easier to simply remove strong, new growth with a knife before replanting each piece. The dead central portions of the plant can simply be added to the compost heap, unless they show signs of disease.
Back to your roots
Plants with rhizomes, corms or bulbs (swollen roots) such as gladioli, iris and crocosmia can also be divided, although the process is slightly different.
Over the course of a few seasons, these plants will begin to form additional tiny bulbs. Gladioli, for example, produce little outgrowths known as ‘cormlets’. These miniature versions of the parent usually require a couple of years’ growth before they will flower, but will reach maturity more quickly if they are given easy access to nutrients, light and water. Separating and planting them a distance away from the parent means that they won't have to compete, and can therefore grow unchecked.
Plants which sprout from rhizomes, such as bearded iris, require different treatment. The long tuberous roots are should be lifted as soon as the plant has finished flowering, and the young rhizomes cut off cleanly with a sharp knife. The next step is to re-plant so that the top of the rhizome sits very slightly above the soil.
Whichever method of division you choose, it is important to get your new plants off to a flying start. Water-in well, as the new divisions will take a while to establish a fully-functioning root system. Regular watering is essential to bring nutrients to these plants. A Hozelock watering system lets you set a regular schedule even if you are not home to care for your plants. It is also a good idea to revitalise the soil with well-rotted organic matter, such as home made compost or organic fertilizer. This is particularly important if you are planning to re-plant in the same spot after dividing your plants.