For many years now, every single plant I bring home gets removed from it's original container and then I use the garden hose to wash off all the soil from the roots, divide and re-pot in my own potting medium. If there are two, three or four plants with roots heavily entangled, I disentangle the roots and divide the plants into individual containers.
I guess I should be honest though ... sometimes I'm not so gentle at untangling roots.
