Experts and BHG readers answer.
The best time to do this would be in the early spring just as they are breaking dormancy. But, if they are very young, you can probably move them if you take a large soil ball with them and water well for the first week or so. It's a bit more iffy doing it now, but small plants may transplant without too much dieback if you do it carefully. Ideally, on larger plants you should wait till spring.