(Image credit: Shutterstock) Peace lily leaves should lie flat with gentle curves along their length. When they start curling inward, rolling at the edges, or folding lengthwise, the plant is signaling stress from its environment. Curling is the plant reducing its surface area as a kind of self-protection. Leaves that once spread wide tighten into scrolls or fold along the center vein, in response to conditions it can't tolerate. 1. Fix your watering schedule Incorrect watering, either too much or too little, is the most common cause of curled peace lily leaves. Both extremes stress the plant, triggering leaves to curl as a protective response. Underwatering causes leaves to curl inward to reduce surface area and minimize water loss through transpiration. The plant conserves whatever moisture remains in its tissues. Soil pulls away from pot edges when bone dry, and the entire plant may droop alongside curled leaves. Overwatering suffocates roots and prevents them from absorbing water properly .…