The good news is that your junipers are tough evergreens and do not require much fertilizer. Using a slow-release plant food like Osmocote is a good way to get them off to a strong start but it is more important that you plant them properly by setting at same level in soil that they were growing and loosening the soil in the planting hole so that the roots can spread out easily. Watering is the essential task as during the first year of life transplants will die from lack of water as they struggle to grow a larger root system. Keep the soil moist but not wet. Use a mulch to seal in moisture but before you add the mulch sprinkle the Osmocote "Outdoor Indoor" (formula with the pink cap or in large bags the formula with a balanced 14-14-14- formula) around the base of each shrub following the package instructions.  Sounds like you are going to have a growing wind break soon. Keep growing, Marianne Binetti