How to Divide a Hydrangea

Select a hydrangea for dividing during the growing season, choosing a healthy shrub that produces masses of blossoms and exhibits uniform growth. If you have numerous hydrangeas, mark the chosen one with a piece of string during the growing season, since you must wait until dormancy to divide these shrubs.

Prune back the hydrangea shrub after it goes dormant for the winter. Trim back the outer shoots to remove any overgrown or broken twigs and branches. Dig up the underground root ball, using caution to avoid damaging the roots. Lift the uprooted hydrangea from the soil and place it on the ground. Cut through the root ball with the sharp edge of a shovel or a hatchet, forming equal portions that contain both stems and roots. Place the cuttings in a bucket of water while you prepare new sites for planting the divisions.

Find a location that receives sunlight during the morning hours and shade in the afternoon. Avoid low-lying areas that retain water after rain and snow.

Dig holes that measure at least 2 feet wide and 1 foot deep. Combine the backfill from each hole with an equal amount of organic matter, such as peat moss or compost, mixing well to form a rich, well-drained medium. Fill the hole with the amended soil to a level just deep enough to allow the roots to remain slightly below the surface of the soil.

Remove your cutting from the bucket of water. Cut off any damaged or broken roots with pruning shears, making clean cuts slightly above the point of damage. Place the roots into the hole, keeping the shrub division centered while you shovel the remaining backfill over the roots. Tamp down the loose soil with your foot to help expel any air pockets from the area around the roots. Apply enough water to provide even moisture throughout the roots.