When is the latest time to sow sunflowers?
Sunflowers can be planted in all four seasons, usually mainly in summer and winter, and the flowering period can last more than two weeks. Besides looking like the sun, their bright and generous flowers are very suitable for ornamental display, and the seeds have even greater economic value, as they can not only be made into the popular sunflower seeds, but also be pressed into low-cholesterol premium edible sunflower oil. Now let us take a look at when sunflowers should be sown!
Sowing time for sunflowers
The sowing time for sunflowers is March to April, the suitable temperature for sowing is 18-25°C, and they sprout about 5-7 days after sowing. The basic principle for choosing the sowing period is to sow appropriately early or late according to the patterns of salinization and alkalization, so that the seedlings avoid salt and alkali damage. Spring sowing or summer sowing is carried out according to the growth period of the variety. Adjust the sowing period according to the patterns of disease occurrence so that it avoids the season when diseases occur frequently. Adjust the sowing period according to growth characteristics so that the flowering and grain-filling period avoids high-temperature weather above 28°C. The sowing method is dibbling, with about 1 cm of soil covering the seeds, and flowering occurs about 50-80 days after sowing, with slight differences in each item depending on the variety.
Growing environment for sunflowers
1. Temperature: Sunflowers are a crop that loves warmth and tolerates cold, with strong adaptability to temperature. The seeds have a very strong tolerance to low temperatures. When the ground temperature is stable above 2°C, the seeds begin to germinate; at 4-5°C they can sprout and take root; when the ground temperature reaches 8-10°C, it can meet the needs of seed germination and emergence. Throughout the entire growth process of sunflowers, as long as the temperature is not lower than 10°C, they can grow normally.
2. Water: Sunflowers are a crop that consumes a relatively large amount of water. The plants are tall, with many dense leaves, and their water uptake is 1.74 times that of corn. However, because their growth and development mostly coincide with local rain and heat, the contradiction between water supply and demand is not prominent, and the water requirements differ greatly at different growth stages. From sowing to budding, not much water is needed; from budding to flowering is the peak water-demand period; and from flowering to maturity, the water requirement is also relatively large.
3. Light: Sunflowers are a short-day crop and are not very sensitive to daylength. They like sufficient sunlight, and their seedlings, leaves and flower discs all have strong phototropism. With sufficient sunlight, the seedlings are robust and can be prevented from growing leggy. With sufficient sunlight in the middle growth stage, vigorous stem and leaf growth can be promoted, normal flowering and pollination can occur, and the seed-setting rate can be increased. With sufficient sunlight in the late growth stage, the seeds are plump and full.
4. Soil: Sunflowers have low soil requirements and can grow in all kinds of soil, from fertile soil to dry land, barren land and saline-alkali land. They not only have a relatively strong tolerance to salt and alkali, but also have salt-absorbing properties. At the same time, sunflowers have well-developed root systems and relatively strong drought resistance. Moreover, the roots and stems of sunflowers have well-developed aerenchyma and are very tolerant of waterlogging.
Growth cycle of sunflowers
1. Seedling stage: The period from emergence to budding in sunflowers is called the seedling stage, generally requiring 35-50 days, or 28-35 days for summer sowing. This period is the stage of leaf and flower primordium formation and floret differentiation. The seedling stage of sunflowers is the stage with the strongest drought resistance; aboveground growth is slow, while underground root growth is faster, quickly forming a strong root system.
2. Budding stage: From budding to flowering, sunflowers generally need about 20 days. This is a period when vegetative growth and reproductive growth proceed together, and it is also the most vigorous stage in their life. This period has the greatest demand for fertilizer and water, accounting for about 40-50% of the total fertilizer and water demand. If the need for water and fertilizer cannot be met in time, yield will be seriously affected.
3. Flowering stage: For a single flower disc of a sunflower, from the opening of the ray florets to the completion of the opening of the tubular florets generally takes 6-9 days. From the second day to the fifth day is the full-bloom period, mostly opening at 4-6 a.m., with pollination on the next morning. Unpollinated stigmas can remain for 7-10 days, but the seed-setting rate of self-pollination is only about 3%, while the seed-setting rate of cross-pollination is high.
4. Maturity stage: The maturity stage of sunflowers refers to the stage from flowering to maturity, 25-55 days for spring sowing and 25-40 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.