Viruses, such as impatiens necrotic spot virus and tomato spotted wilt virus, may cause leaves to wilt. Signs include leaf spotting followed by wilting. Affected plants should be removed to prevent the virus from spreading to other plants in the garden.
Wilting of impatiens indicates that the flowers are in need of water. Overwatering, however, also may cause wilted leaves. Provide enough water for the soil to be moist throughout, but not so much as to leave roots sitting in soggy soil.
Excessive heat and sunlight may cause impatiens to wilt. While some species of impatiens tolerate full sun, others prefer shade. Similarly, some tolerate morning sun, but most benefit from afternoon shade.