You can usually tell the right time for re-potting by the fact that roots appear on the surface. The reason for this is that plants produce more and more roots overtime, which take up all the soil in the pot. Roots showing on the drainage hole are not a certain sign for re-potting. If you want to be sure, lift the plant out of the pot. You can thus inspect the existing roots. Re-potting is also necessary when a white crust can be seen on the soil. This may be caused by too hard water being used or due to salination.
The root bale can most easily be detached from the plant container for re-potting when the substrate or soil is slightly dried on the surface. Lift the plant out of the pot and place it in a water bath. Old and dead roots must be cut off before re-planting. It is also good to loosen the roots a little. Then fill the new, larger pot with a drainage layer, e.g. of fine gravel, polystyrene balls or expanded clay. There then follows a layer of humus-rich plant soil. Place the plant in the centre of the pot so that it is at the same height as in the previous pot. Then fill the flower pot completely with soil, also around the edge of the pot. Remember, however, not to fill the pot right up to the rim, so that you have some ""air"" for watering. Then press down lightly – and you have already done something good for your plant! After re-potting, you should not forget to water so that the gaps in the soil are filled.
The best time to re-pot plants is at the beginning of the growth period. The season is not very important here. However, you should be careful if the plant is in its rest period. Then you should not re-pot the plant, as otherwise moisture accumulates in the soil and the roots begin to rot. The following generally applies: house plants should be re-potted every two to three years. Alternatively, if it is a large plant, it is often sufficient to remove the top layer of soil and replace it with new, nutrient-rich soil.