After a period of gradually acclimating to the wind and sun outdoors, young plants are ready to go into the garden. This process can be traumatic for the plants, so try to choose an overcast day or wait until late in the day to plant. This spares the seedlings extra stress from bright sun while they cope with the inevitable transplant shock. Their adjustment is much easier, too, if their new soil is loosened, moist, and reasonably warm.
One way to avoid problems as seedlings mature into full-sized plants is to allow sufficient space between them when planting. Although the garden may seem bare at first, giving plants the room to grow without being crowded ensures good air circulation, which deters diseases. Mulch the bare soil between small plants to discourage weeds from filling the space while the seedlings grow.