Hosta are one of the most forgiving of plants when it comes to digging, dividing and replanting. They are best divided and replanted in the spring or early fall when the heat of summer has passed and the cold of winter is not yet upon you. Plant hosta divisions in the same filtered shade to deep shade conditions they were growing in previously.
Keep hosta divisions moist digging and dividing them as close to replanting time as possible. When the divisions must be out of the ground for more than a few minutes, pack the roots in wet soil and wrap in burlap to prevent dry out.
Dig a hole with a hand trowel that is at least twice the diameter of the division. Loosen up the soil to ease new root penetration for the division planting. Place holes for multiple divisions at intervals of at least one foot apart.
Set the hosta plant in the prepared hole ensuring that the crown of the new division sits in the soil at the same height that it was planted previously, not lower or higher.
Back fill the loosened soil around the roots compacting lightly to ensure good root to soil contact.
Water in well to collapse air pockets and support the roots. Mulch around the base of the hosta with shredded bark, compost or cocoa bean hulls to hold moisture in the soil and protect the new tender roots that will soon form.