Growing plants is a popular and easy method to facilitate preschoolers' scientific exploration and positive attitude toward the environment, as it creates an awareness that nature is a magical place to be explored. This study examines a year-long garden-based curriculum in South Korea, specifically a cotton project, and its effects on 4- to 6-year-old children's (n = 165) scientific and nature-friendly attitudes. Classroom observations and teacher interviews were obtained for qualitative data and scientific attitudes and nature-friendly attitudes were collected for quantitative data. The results indicated that planting cotton and observing the process of its growth provided opportunities for developing a scientific attitude of curiosity and inquiry. In addition, the meaningful direct and concrete experience with the natural environment opened the children's eyes to the significance of nature and the value of harmony with the natural world, resulting in increased nature-friendly attitudes. The critical roles of the teacher are addressed in implications.