When you start tree and shrub seeds inside, you need to harden them off before planting them outside. This is a process where you take the seedlings outside for a little each day, gradually increasing the amount until planting day.
The inside environment is usually very calm in comparison to the wild outdoors. Light is lower. There is no wind to disturb the plant. Temperatures don't fluctuate as much. If you were to take them straight outdoors, the differences would be great enough that the seedling may go into shock, which could stunt or kill the plant.
Simply start taking the seedlings outside a week or two before the planting date. Water them less frequently to help get them ready for transplantation. Start with an hour and increase the time daily.
