The Growth Process of Sunflowers: Latest Detailed Guide
The growth period of a sunflower refers to the number of days from emergence to seed maturity, generally 85 to 120 days or more. The length of the growth period varies depending on the variety, sowing date and cultivation conditions. The entire growth period is divided into four growth stages: seedling stage, budding stage, flowering stage and maturity stage. Let's take a look at the growth process of sunflowers below!
Seedling stage
The period from emergence to budding in sunflowers is called the seedling stage, generally requiring 35 to 50 days, or 28 to 35 days for summer sowing. This period is the stage of leaf formation, flower primordium formation and floret differentiation. The seedling stage of sunflowers is the stage with the strongest drought resistance; above-ground growth is slow while the underground root system grows rapidly, quickly forming a strong root system.
Budding stage
When a star-shaped body 1 cm in diameter appears at the top of the sunflower, it is commonly known as budding. From budding to flowering generally takes about 20 days; this is a period when vegetative growth and reproductive growth proceed together, and it is also the most vigorous stage of the plant's life. During this period, sunflowers need the most fertilizer and water, accounting for about 40 to 50% of total fertilizer and water demand. If the need for water and fertilizer cannot be met in time, yield will be seriously affected.
Flowering stage
When 75% of the plants in a sunflower field have their ray florets open, the flowering stage begins. It generally takes 6 to 9 days for a single flower head to go from the opening of the ray florets to the completion of the opening of the tubular florets, and from the second day to the fifth day is the peak flowering period of that inflorescence. The number of florets opening during these 4 days accounts for about 75% of the total number of opened florets. Flowers mostly open between 4 and 6 in the morning, and are pollinated the next morning. Unpollinated stigmas can remain without wilting for 7 to 10 days. The seed-setting rate of self-pollination in sunflowers is extremely low, only about 3%, while the seed-setting rate of cross-pollination is high. However, if temperatures are high, there is much rain, humidity is high, light is insufficient, or the soil is dry, the seed-setting rate will be greatly reduced. Therefore, measures such as adjusting the sowing date, timely fertilization and watering, controlling pests and diseases, and introducing bees or artificial supplementary pollination can improve the seed-setting rate.
Maturity stage
The maturity stage of sunflowers refers to the stage from flowering to maturity, 25 to 55 days for spring sowing and 25 to 40 days for summer sowing, with differences among varieties. About 15 days after flowering and pollination is the seed formation stage. The maturity stage of sunflowers requires clear weather, a relatively large temperature difference between day and night, and suitable soil moisture.