Leaves on what? Tomatoes? If so, take this question to the tomato forum and you should get some responses. They will want details, such as what variety, are they curling up or down, the weather and watering info, color of the leaves. You get the picture. In fact, pictures will make it much easier to figure out what's going on without making too many wild guesses. There are many potential causes of curling leaves and getting a diagnosis of the cause is essential before a treatment can be suggested.

If I guessed wrong and it's not tomatoes, there are many plant specific forums here where you can post your question.

Sandy

Here is a link that might be useful: Tomato forum at Garden Web