The time of year to pick sunflowers depends in large part on when you plant the seed. Wait until after the last expected frost for your area, when the soil temperature has warmed to at least 50 degrees Fahrenheit. Sunflowers germinate in five to 10 days and take 50 to 80 days to reach the harvest stage from seed. Planting at spaced intervals of two to four weeks in the spring will give you a longer harvest as the flowers ripen in succession as they were planted.
If you plan to harvest the seeds from your sunflowers, let them dry in the sun, waiting for the back of the flower head to turn brown. The seeds should be ready to harvest about three months after planting, So, if you plant in April or May, you can expect to harvest in mid to late summer.
For Cut Flowers
To enjoy the beauty of fresh, cut sunflowers, harvest earlier, just as the flower is opening. The rays should be perpendicular to the central disk. With a successive planting schedule, you should have a continuous harvest through the summer once flowering starts, which could be as early as late May to early June if you plant in early April depending the cultivar.
Time of Day
Knowing what time of day to harvest sunflowers is as important as knowing the time of year to expect sunflowers to be mature and ready to pick. You will get the best results with sunflowers by harvesting in the cool of the morning, just after the dew dries, or in the evening cool at sunset. Protect the flowers from exposure to excessive moisture.