Sweet potatoes originally are tropical perennials, though they appear to be annuals when cultivated in temperate regions. The tubers are transformed roots with no distinct maturation period; as long as the environment is suitable, the longer the growing period, the larger the tubers can grow, and the higher the yield.
According to high-yield experiences and experimental results from various regions, it is widely believed that early vine planting is one of the important measures to achieve high yields. Planting vines early not only extends the growing period but also significantly benefits the development of the root system and the initial formation of tubers, thus increasing yield.
Planting vines late, on the other hand, shortens the growing period, which affects the yield. This is because the period from vine planting to harvest can be divided into two stages: the first stage focuses on growing stems and leaves, while the second stage focuses on growing underground tubers. Therefore, the later the vines are planted, the significantly shorter the second stage for growing tubers, resulting in reduced yields.
Moreover, planting vines late also affects the quality of the sweet potatoes. Late planting reduces the content of starch, carotene, and vitamin A in the tubers; it also results in the tubers being long and slender, fibrous, and of poor quality.
However, sweet potatoes are warmth-loving crops and cannot grow well without sufficient warmth, so planting vines too early can also affect the yield.