The best time to divide spring and early summer blooming perennials is in the fall - divide and transplant at least six weeks before the first hard freeze.
The day before, water your plants and cut foliage by a third.
If possible, the best time to divide is on a cloudy day early or late in the day. Plants recover more quickly if the sun isn’t beating down on them.
For larger plants where lifting the entire root ball would be difficult, remove a portion at a time by slicing through the root ball with a spade and then digging up that portion.
Very large, dense root balls, such as those of daylilies or Siberian irises, may require prying apart with two spading forks. You may even need to use a small hand ax to hack through difficult root balls, but this should be a last resort.
Break the root ball into smaller sections with your hands when working with delicate plants.
If your perennial has a rhizome or tuber that grows horizontally, like bearded iris, dig it up and use a sharp knife or pruning shears to cut it into pieces. Leave at least one bud and some roots on each piece.
Dampen newspaper and wrap your perennials in the damp paper and place them in the tub or on plastic in a cardboard box if you are bringing them to our plant share.
If replanting at home, prepare the soil and add some enrichment, water well and give your new division time to settle in before the first frost.
There are many good tips on the internet and many YouTube videos that you may find helpful.