Divisions

Most gardeners will be familiar with dividing herbaceous perennials. This usually arises because the shoots become overcrowded and the thick clumps that develop often have woody or bare centres. Borders are rejuvenated by carefully lifting the clump (‘crown’), preferably with a ball of soil, teasing off most of the soil carefully from the roots and splitting it with back to back forks for good leverage. Whilst smaller specimens can be pulled apart by hand, some are so tough as to require knives or spades. This division can be undertaken in the autumn as plants die down, but is usually better done in the spring as the new shoots appear. The younger sections with strong shoots can be replanted in prepared ground (normally with many surplus pieces to give away or sell). This should be done before the roots have dried and the plants are then watered in.

Alpines (cushions, carpets, mat formers, rosette types) lend themselves to increase by division which is popular because it is cheap, simple and quick. Commonly the divisions are made in mid-spring as the plants begin to grow and they establish most easily. The only problem for gardeners is that it rather spoils the rock garden if separate stocks are not kept; they can restrict themselves to taking rooted pieces from the edge of the clump. Whilst gardeners can plant these straight into the garden, commercially they are grown on in pots until an attractive plant is produced. This is enhanced by the addition of a suitable grit on the surface of the compost.

Aquatic plants can be dealt with in essentially the same way as herbaceous perennials.Water lilies are usually lifted in late spring and the growing shoot (the ‘eye’) is cut away with a piece of the tuber and some root. These pieces are firmed into a pot or basket containing a minimum of sieved clay loam and powdered charcoal and grown on with the water level at the rim. Marginals such as reed mace and sweet flag are divided in late spring. The pieces are cleaned up of excess and dying leaves before replanting. Submerged plants (oxygenators) tend to be vigorous and need to be reduced on a regular basis. If more plants are wanted then pieces broken off can be tied in bundles with wire and returned to the water.
House plants that develop clumps such as Maranta , spider plants (Chlorophytum), African violets (Saintpaulia) and mother-in-law’s-tongue (Sansevieria) can be propagated by divisions. This can usually be done by breaking the clump with the fingers to minimize damage to the roots, with help from a knife only to get started if too tough. The pieces are put into a pot just big enough to take the roots with potting compost. Care needs to be taken to fill without leaving cavities by constantly tapping the pot on the bench as it is filled. The plants need to be given a warm environment, ideally in a propagator unit or polythene bag, which will help reduce water losses until established.

Suckers produced by many trees and shrubs can be a problem as they divert energy from the main purpose of the plant and make a messy area around the base. However, they can be used as a source of new plants in the case of many, such as Rhus typhina, raspberries and woody house plants or palms. (Suckers arising from grafted material, e.g. roses or apples, will reproduce the rootstock.) Soil from around the base of the plant is removed to expose the point where the suckers can be removed with a knife or pruning shears, ideally with some root attached. Their relatively large size and lack of root means they need to be kept watered until established. They are normally heeled into a trench and in the nursery protection from sun and wind is provided over the next year until there is a good root system.