This group includes astilbes, hostas, daylilies and many ornamental grasses. You can also pry apart these roots with back to back digging forks. Keep at least one developing eye or bud with each division. If larger plants are wanted, keep several eyes. Bearded irises are the most common perennial with this type of root system.
Divide irises any time between a month after flowering until early fall.
Cut and discard the rhizome sections that are one year or older. Also, inspect rhizomes for disease and insect damage. Damaged rhizomes should be trimmed and treated, or discarded if too badly damaged. Iris divisions should retain a few inches of rhizome and one fan of leaves, trimmed back halfway. Replant with the top of the rhizome just showing above soil level.