Hydrangea plants grow into large shrubs and take over gardening spaces if left to their own devices. Split hydrangea plants to limit the size of an existing plant and to add a new one to the garden. Smaller plants need only be split once while larger plants do well when split into several smaller hydrangea plants.
Wait until the hydrangea plant is dormant before splitting the plant. Early spring is the best time to split hydrangea plants to avoid stressing the plant.
Tie the limbs of the hydrangea plant with the ropes into sections for dividing. This keeps the hydrangea bush contained for easy transport. Confining the branches also exposes the root stem for easier digging.
Dig up the root ball of the hydrangea plant, taking care not to damage any of the roots. Start digging a shallow trench at least 2 feet from the main stem and continue digging until you have located the outer section of the root ball.
Lift the entire root ball from the hole and sever the ball in the middle with the shovel, into two sections. Divide the sections even further if the remaining root balls are considered too large for the new planting space. Use a hacksaw if the root balls are too large for the shovel to cut through.
Dig the new hole for the hydrangea plant and fill partially with water. Loosen the soil along the sides of the hole so the roots can penetrate easily and re-establish themselves quickly. Add a layer of mulch or organic matter in the bottom of the hole.
Spread the root ball slightly to expose more of the root system of the hydrangea plant. Place the shrub into the hole making certain the new planting depth matches the old depth. The base of the hydrangea stems will show signs of the soil line. Plant no deeper than these lines. Remove the rope from the plant. Water the transplant daily until the hydrangea plant has established itself in the new location.