Clay soil is not an ideal planting medium for shrubs or bushes, but if you have a yard filled with it, there's often little choice. The soil can be amended, but it must be done in such large amounts that it is expensive and difficult for the home gardener to accomplish without special equipment. Instead, the best way to plant shrubs in clay soil is to choose plants that are tolerant of heavy soil, and dig the holes properly to allow as much drainage as possible.
Choose a shrub that tolerates clay soil. Look for shrubs that don't require well-drained soil. According to Bachman's Garden, shrubs that grow well in clay include Alpine Currant, Arborvitae, Forsythia, Lilac, Russian Olive, Snowberry and Redtwig Dogwood. Other shrubs that can withstand clay soil, as noted by Bachman's, are Barberry, Pagoda Dogwood, Sumac, Winterberry and most junipers.
Pull away the soil from the top of the plant until you reach the first roots.
Measure the distance between the top roots and the bottom of the lowest roots. This measurement will tell you how deep to dig the hole.
Measure the width of the root ball, and double the measurement. This is how wide the hole will need to be dug.
Dig a hole using the measurements taken in Steps 3 and 4. Make the center deepest, and the edges shallower, similar to a bowl shape.
Place the shrub in the hole, making sure the top roots are at the same level as the top of the hole.
Fill the hole with the same soil you removed from it.
Tamp, or press down the soil lightly, taking care not to compact it too much.
Water the newly planted shrub.