4. Not watering properly. Both over watering and under watering are a problem. If you let the plants get too wet it is a recipe for disease. If they get too dry they will wilt. The key is frequent consistent watering. In the beginning of the season a light watering will due. But as the season progresses, deep watering is required to encourage deep root growth. Plants with deep roots will survive a dry spell much easier than plants with a shallow root system.
From My Garden