The principles of planting and repotting are the same. Plants need to be firm in the compost to prevent air pocket around theit roots and have adequate drainage to avoid waterlogging.
All plants grown in containers should be planted the same way. When you are potting, choose a container 5 cm (2 in) larger than the rootball of the plant. Remove the plant from the original container and gently tease out the roots if they have become congested. Trim off any damaged roots. Put a good layer of crocks, broken tiles or stones at the bottom of he container and then a layer of compost. Put the plant in the container, making certain that the soil level is the same in the new container as it was in the old. Add compost around the sides of the pot making sure that it is pressed firmly against all the roots.
Firm the soil with your hands or a dibber but don’t ram the compost down too tightly. Rap the container down on the hard surface two or three times to shake out any air pockets. Water thoroughly and top up the level with more compost as it settles.
Young plants need to be transferred from small pots to larger pots, depending on their rate of growth. This should be done in stages. Always transfer a growing plant to a pot just larger than the one it is in at present, about 5 cm (2 in) diameter larger is ideal. This keeps the growth at a steady rate. If you potted on into a pot that was considerably larger, the roots would spread out too quickly which upsets the growing balance of the plant.
Repotting the plant
How often a plant should be repotted is a difficult question to answer. At one end of the scale, repotting may not be possible. Large raised beds, especially when they contain permanent trees or shrubs, cannot easily be emptied. In these cases remove as much of the top compost as possible without damaging the roots of the plant and then replace it with fresh and add fertilizer. Otherwise, in containers that can be moved the compost should be emptied out and replaced every other year, and this should be done every year when the plant is growing vigorously.