How to move a deciduous shrub
You can move even mature shrubs with relative ease as soon as they drop their leaves, when the soil is warm and it is still pleasant to work outside.
Make sure the soil is moist around the roots so that you move the shrub with a good root ball – a two-gallon can, thrice, slowly, under the whole canopy should do it, or an overnight dribbling hose.
Reduce the shrub to manageable proportions, cutting out any really old wood and preserving some of the youngest. Flowering will be reduced next year while the shrub puts on new growth.
Get a feel for the size of the roots by investigative digging. They may extend as far as the old canopy, but you are bound to sever some during the operation – don’t worry unduly.
Prepare the new site before you dig up the shrub, incorporating compost and two fistfuls of bone meal into the pit and the removed soil. Fill the pit with water and wait for it to drain.
Manhandle the shrub into its new site, check its position and backfill with the removed, improved soil. Firm the root area with your boot. Water well once, apply a compost mulch over the root area – and wait optimistically for spring.