If the tips of the plants' leaves are still green, they will probably recover when the temperatures climb again. If the leaves are completely yellow, you should pull the plants and start over. To prevent this from happening again, wait to plant until the nights stay above 50F, or provide some protection for your young plants. In particular, they may need some cover on chilly spring nights. You can use a milk jug with the bottom cut away as a temporary greenhouse for a week or two, until the plant is too big for the jug and the nights are warmer. You can leave the cap on the milk jug, but be sure to uncap the jug during the day when temperatures are above 50?F. Other devices have been developed in the last few years, such as water-filled tubes to place around the plants to insulate them against cold air. Examples of these products are Wall O' Water and Kozy-Coat.