How to Prune Indian chrysanthemum?
Once flowering is over in late autumn, cut the whole plant down to 20cm (8in) tall.

Indian chrysanthemum · Chrysanthemum indicum
Also known as: Japanese chrysanthemum; winter aster
Grow in a well-drained, fertile, moisture-retentive soil in full sun. In cool regions, lift the plants in autumn, before the first frosts and store the crowns in trays of just moist compost in frost-free conditions until spring. In areas where temperatures fall no lower than -5˚C (23˚F) in winter, plants may be left in the ground and protected by a thick mulch over winter, carefully removing this in spring, after the risk of frosts has passed.
Once flowering is over in late autumn, cut the whole plant down to 20cm (8in) tall.