1, temperature condition
The suitable temperature for the growth of calendula is 7 ~ 20℃, the seedlings can tolerate the low temperature of -9℃ in winter, and the suitable temperature for the adult plants is 0℃. If the temperature is too low, it needs to be protected by film, otherwise the leaves will be easily frozen. When the temperature is above 10℃ in winter, calendula grows white. In summer, the temperature rises, the stems and leaves grow vigorously, the flowers become smaller and the petals decrease obviously. Marigold seedlings should be slightly wet, which is beneficial to the growth of stems and leaves and improves the cold resistance in winter. Adult plants should be slightly dry, which can control the growth of stems and leaves to avoid excessive growth.
2. Lighting conditions
Calendula likes cold-resistant, heat-resistant and sunny environment, especially suitable for outdoor seedling raising or greenhouse cultivation in winter, which is very beneficial to the growth of stems and leaves, and the seedlings grow short and orderly. When there is too much rain and snow and insufficient light, the basal leaves are easy to turn yellow, and even the roots rot and die. The soil should be fertile, loose and well-drained sandy loam or cultivated land. The soil pH should be kept at 6 ~ 7, so that plants have many branches and flowers are large and dense.