Have you considered growing them from seed? A seed-grown specimen would probably catch up to and surpass one that started out as a 3-gallon container grown plant within about 3 or 4 years. After that, it's also likely to have a better adapted root system.

If you do go with potted ones, be sure they are not pot-bound and address any root issues before putting them in the ground.

Planting a Tree or Shrub