How to Grow Ornamental Sunflowers? A Detailed Guide to the Latest Varieties and Planting Methods
Ornamental sunflowers are annual flowers of the genus Helianthus in the Asteraceae family, with plants growing 90 to 300 cm tall and a blooming period from July to September. Flower colors include golden yellow, red and bicolor, and they are generally planted in large drifts. When in bloom, their golden brilliance is dazzling, offering both a wild charm and a spectacular sight, and they are widely used for cut flowers, potted flowers, dyed flowers, courtyard beautification and flower border creation. Now let us take a look at how to grow ornamental sunflowers!
Growth Habits
Ornamental sunflowers are native to North America. They prefer a warm, slightly dry environment with plenty of sunlight, are drought-tolerant, and can be grown both in pots and in the open ground. When grown in the open ground with long hours of sunlight, they often bloom slightly earlier, and a temperature difference of 8-10°C is most favorable for stem and leaf growth. Most are single-petaled varieties, though double-petaled varieties also exist. Taking dwarf potted varieties as an example, it takes 50-60 days from sowing to flowering.
Propagation Methods
Ornamental sunflowers are propagated from seed. Sowing is generally carried out in April, and the optimum temperature for germination is 15 to 18°C. They can be sown in shallow pots or shallow boxes, and the medium should be loose, with good water retention and sterile. Sowing is best done by dibbling, with 2 seeds per hole. After sowing, cover with 1 to 2 cm of medium to maintain the moisture needed for germination, increase the stability of the seedlings during the seedling stage, and reduce the occurrence of seed-shell-held seedlings. Germination generally occurs 7 to 14 days after sowing. After emergence, pay attention to ventilation and cooling, control humidity, and gradually expose the seedlings to light.
Timely Planting Out
After the ornamental sunflower seedlings have all emerged, thin them out gradually, leaving 1 plant per hole. They can be planted out when the seedlings are 7 to 8 cm tall. A sandy soil rich in humus and with good drainage is best for the potting mix. When planting out, apply sufficient base fertilizer at the bottom of the pot. When lifting the seedlings, carry as much soil as possible and damage the roots as little as possible so that the plants recover quickly.
Planting Management
1. Light: Plenty of sunlight is needed throughout the entire growth and development period. If there is continuous rain or the plants are grown in a semi-shaded environment for a long time, the stems will not be upright, the leaves will be soft, drooping and yellow-green, and the flower discs will be small and irregular.
2. Temperature: The optimum growing temperature is 21-27°C during the day and 10-16°C at night. If the temperature is on the low side, growth will be slow and the flowering time will be affected. If the temperature exceeds 30°C, the stems and leaves tend to grow leggy and the flowering period is shortened.
3. Water: Ornamental sunflowers have large plants but relatively little medium, so they must be watered promptly during the growing period, otherwise the leaves easily become dehydrated and wilt. However, they should not be too wet; if the humidity is too high, the lower leaves easily turn yellow.
4. Fertilizer: During the growing period, fertilize ornamental sunflowers once every 20 days, usually by alternating applications of various compound fertilizers diluted 1:800 in water, but before flowering, apply 2 to 3 light applications of phosphorus and potassium fertilizer to promote flowering.
5. Cultivation: For potted plants, do not pinch out the growing tip; single flowers are preferred. For tall varieties, 20 days after germination, a 0.25-0.4% B9 solution can be sprayed on the leaves to control plant height. For flower bed display, the growing tip can be pinched out once, which can produce 4-5 flowers.