Root pruning promotes the growth of new roots which are more efficient at uptaking waters and nutrients. When a Haworthia is taken out of the container for caring or propagation, it is recommended to prune its roots before planting it back.
After cleaning the growing medium, remove any dried, hollow or rotting roots which don’t function but can cause rotting. Fine roots can also be safely removed if doing so makes the operation easier. These roots are likely to not survive when the plant is later dried for healing its wounds.
If a Haworthia has a big underground stem, the stem ideally should be trimmed. Because new roots rarely grow out of the stem with thick calluses, trimming it not only makes rooms for new roots but also reduces the chance of rotting. However, this will create a big wound and takes more time for the plant to recover. Therefore the trimming should be done only for a mature plant which can survive after a long recovering period.
After pruning, treat the wounds properly to encourage a faster recovery.