To keep these plants healthy, ease the root ball out of the tub and, using a sharp knife, cut a straight line through opposite sides of the root ball – 8 cm in from the edge of the widest part of the root ball, as shown in the diagram. The space provided by the reduced root ball and the amount of potting mix that falls away from the root ball will allow space for enough fresh potting mix to be added to the tub. After checking that the drainage holes in the base of the tub are clear, replace the plant in the pot with fresh organic potting mix.
Trimming plants in this manner provides space in pots without damaging all the delicate feeder roots. Place a durable plant tag into the top of the fresh mix on one of the sides where it was trimmed. When you need to re-pot the plant again, make the pruning cuts at right angles to the previous cuts.
Tip pruning the foliage will compensate for the temporary loss of roots and prevent the plant becoming straggly.