Hardening Off Tomato Transplantstomato seedlings to outdoor conditions. These plants have spent their short lives in a warm, sunny, protected place and won't fare well if you don't expose them slowly to the elements.
A few days before you're ready to begin hardening plants off, reduce amount of water you give them, and cease fertilizing until they are planted in the garden.
About 10 days before you intend to plant, put your transplants outdoors in an area where they'll be protected from the direct sunlight and wind. Leave them out for a few hours and bring them back inside. Repeat this each day, gradually increasing the amount of time they're outside and the degree of exposure to sun and wind. After a week or so, leave the transplants out overnight. If frost threatens, bring them indoors.
If you harden off your plants properly, they'll be strong and able to withstand full sun, strong breezes, and all the challenges they'll meet in the garden.