Domesticated about 1000 BC in their native United States, sunflowers mature in 90 to 100 days. The flower is really hundreds of tiny flowers growing together in the center disk. The centers of sunflowers contain both male and female parts and the outer petals are ray flowers that do not produce seeds.
Varieties of sunflowers are available in heights from a foot high up to 12 feet high, with many cultivars available. They have been extensively hybridized and hybrids come in all shades of yellow, gold, rust and cream, with many bi-colored varieties.
Plant sunflowers in full sun in early spring; sunflower seeds will germinate when soil temperatures are as low as 46 degrees Fahrenheit if the seed is fresh. The young plants are not damaged by frost and will bounce back quickly, while mature specimens tolerate temperatures down to 25 degrees Fahrenheit for short periods.
Thin seedlings when they are about 6 inches high, to stand 3 to 4 feet apart for giant specimens and about 1 foot apart for dwarf varieties. Space rows 20 to 30 inches apart.
Practice crop rotation when growing sunflowers. Although they are subject to few pests and diseases, they are susceptible to verticillium wilt, which can stay dormant in the soil for several years. To guard against diseases ravaging your crop, allow three years between growing sunflowers in the same location.
Protect Developing Seedheads
Squirrels and birds ravage sunflower seed heads. The birds alight on the flower heads and upper stems, while squirrels climb the thick reed-like stems to reach the seeds. To protect your crop of seeds from these scavengers, cover them with small paper bags, such as lunch bags.
Secure the bags to the sunflower's stem with string or with a clip-style clothespin. Put the bags on as soon as the outer seeds begin darkening, or when you notice bird or squirrel activity.
Sunflower seeds are ready to harvest when the back of the seed head turns yellow or brown, about 90 to 100 days after sowing seeds. Remove the entire seed head and place in a cool dry place to complete the drying process. When completely dry, remove seeds by rubbing your hand over them. Store loose seeds in cloth or paper bags; storage in jars or plastic bags can encourage the growth of mold.
Roast sunflower seeds by placing on a baking sheet in a single layer and place in a 350-degree Fahrenheit oven for about 10 minutes. If desired, they can be salted prior to roasting by soaking in a strong salt water solution overnight. Drain well and allow excess moisture to air-dry before roasting.