Transplant shock can set your young plants back considerably. To avoid this, pick a sunny afternoon to put your plants outside and gradually expose them to the cooler temperatures over a period of two weeks or so. Move them from your greenhouse to a cold frame, seed house, cloche, under a row cover, or to a protected outdoor area. Uncover them a little more each day, protecting them again each night from the cold until they gradually adapt.
An application of SeaGrow or SuperThrive (see Fertilizers) will reduce transplant shock further and make your starts stronger when transplanting. Also be sure to protect your tender plants from slugs and insects (see Pest Control).