Lilac bushes are spring blooming plants with aromatic flowers. The densely growing limbs of the bush are propagated through division. According to the North Dakota Extension Service, the best time to split and transplant a lilac bush will be in the late fall or early spring. If transplanting in the early spring, division should be completed prior to the leaves fully emerging from tight buds. The new location must have access to full sun to enhance blooming. The soil must also be well drained, preferably with a rich soil content.
Remove all dead branches from the lilac bush. In most cases, the interior of the lilac bush may contain dead branches from previous years growth. Bend the ends of the upper portion of the branch over. If the branch breaks easily and the interior wood is not green, that branch is dead. Cut the dead branch down to the existing soil line.
Select outer branches of the lilac bush to be split from the mother plant. Typically these smaller branches, less than 18 inches high, will contain enough material in the root ball for a successful split.
Push the sharp end of the shovel, its full length, between the selected split and the mother plant. The shovel tip will sever any roots connected to the mother plant.
Set the point of the shovel to the outside edge of the selected split. Push the shovel down, using your foot on the top edge of the blade. Work the blade under the roots of the lilac split.
Pull the shovel handle back towards you. This will pop the selected lilac split from the ground. The top of the root ball should resemble a large "eye" the same size as the width of the shovel blade, and approximately 4 inches to 6 inches across. The size of the root ball will depend on the size of the branches that are split from the mother plant.
Dig a transplant hole for the lilac split. The transplant hole should be two times to three times the size of the root ball. The larger the transplant hole, the better the roots will take hold in the new location.
Place the lilac split root ball into the transplant hole. Keep the original soil line on the lilac split, aligned with the ground level in the new location. Lilac splits that are planted too deep, may fail to bloom.
Back fill the native soil around the root ball. Pack the soil, with your hands into the hole and around the roots.
Water the new transplant several times, to remove air from around the roots and increase the contact between the root ball and the soil.