|Germination||Direct sow in early spring after the danger of frost has passed. The seeds can be sown as late as 100 days before killing frost. Sow the seed at 1/2 inch deep and keep the soil moist until they sprout. They should germinate in 7-30 days but sometime it takes longer. The optimum soil temperature for germination is 68°F--86°F. The first blooms appear 60--90 days after emergence. Be patient!
Notes: What is usually called the flower is actually a head (formally composite flower) of numerous flowers (florets) crowded together. The outer flowers are the ray florets and can be yellow, maroon, orange, or other colors, and are sterile. The florets inside the circular head are called disc florets. The disc florets mature into what are traditionally called "sunflower seeds", but are actually the fruit (an achene) of the plant. The true seeds are encased in an inedible husk.
Sunflowers in the bud stage exhibit heliotropism. At sunrise, the faces of most sunflowers are turned towards the east. Over the course of the day, they move to track the sun from east to west, while at night they return to an eastward orientation. This motion is performed by motor cells in the pulvinus, a flexible segment of the stem just below the bud. As the bud stage ends, the stem stiffens and the blooming stage is reached. Now the stem is frozen, typically in an eastward orientation. The stem and leaves lose their green color. The wild sunflower typically does not turn toward the sun; its flowering heads may face many directions when mature. However, the leaves typically exhibit some heliotropism.
|Scarification / Stratification||No|
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