Transplanting to the garden:
Toughen your plants for outdoor growing conditions by hardening off. Two weeks before outdoor transplanting time, stop feeding and slow down on watering. About a week before you plan to plant out the seedlings, put them outdoors in a protected area, out of direct sun and wind. Leave them outdoors for only 1 hour at first, then 2 hours, then a morning, until they are used to a full day. Water frequently.
Transplant on a cloudy or drizzly day or in early evening to spare transplants from the sun’s heat. Water the plants before you start. Dig a hole slightly wider than and of the same depth as the container. (Plant tomatoes deeper, so that roots form along the stem. See Tomato Trench Planting
If your transplants are in plastic or clay pots, turn the pots upside down and slide out the plants. Whack the pot with your trowel to dislodge stubborn ones. Plants in peat or paper pots can be planted pot and all.
Gently place the plant in the hole, and spread out roots of plants that aren’t in pots. Slit the sides of peat pots to open them up for better root penetration after planting. Stripping away the top rim of the pot above the soil line is also important, because if even a small piece of peat pot is exposed after transplanting, it will draw water from the soil surrounding the transplant’s roots, leaving the plant in danger of water stress.
Fill the hole and tamp with your hands, forming a shallow basin to collect water.
Slowly pour plenty of water—at least a quart—at the base of the transplant. Keep transplants well watered
until they become established and start showing new growth.
Transplanting large plants: Sometimes a favorite tree or shrub gets too big for its place or is threatened by construction. Or maybe you just want to move a certain plant to a different spot in the landscape. If hard work doesn’t scare you off, consider transplanting.
When handling seedlings, hold and move them by grasping a leaf between thumb and forefinger. Yanking up seedlings by their stems will damage roots.