There are many varieties of sunflowers – both wild species and domestic. They are easily recognizable as an ornamental flower in a garden or bouquet. Sunflowers can also be an agricultural crop! Sunflowers are grown and harvested for their seeds which can be used for birdseed and livestock feed. They confectionary and oilseed versions for human consumption is ideal for snacks, salad toppings, pressed into cooking oil, and more!
Sunflowers are native to North America and thought to have originated in the desert southwest (think Arizona and New Mexico). There are both annual and perennial varieties. The variety that farmers grow for seed is an annual which means that it completes a full life cycle seed to death in one year or one growing season. Because they typically grow in arid climates sunflowers can have deep roots (usually 1 to 3 feet deep, but occasionally up to 5 feet deep). This allows them to maximize soil water and reach water in dry growing regions.
The first step in the sunflower life cycle is the seed. Seeds need to be planted at a depth of 1.5 to 2.5 inches. Smaller seeds should be planted closer to the surface. Larger seeds can be planted deeper. In most agricultural operations seeds of the same size will be selected so a uniform planting depth can be set on the planting implementation. When planting, the furrow of soil needs to be closed over the seeds providing seed-to-soil contact. This helps water absorption and ultimately germination. The sunflower seed has a woody hull and this extra barrier makes seed-to-soil contact more important than with other seeds that don’t have a woody hull, like corn.
Once the sunflower seeds sprout they begin growing a thick stem that will support the heavy seed head. Sunflowers can grow six feet tall or more (some varieties get up to 16 feet!) and the seed head with its hundreds of seeds will weight several pounds.
The flower will form and the seeds will mature relatively quickly – within 85 to 95 days of planting. Each flower head can reach over 12 inches in diameter. They earned their name because their are heliotropic. Sun flowers will turn their flowers to follow the movement of the sun across the sky east to west. But this only happens in the earlier stages of flowering before the head is heavy with seeds.
The seeds are left on the plant to dry in the field and then are harvested when the plant is dead and dry. This is similar to field corn. It is easier to harvest dried plants as they won’t clog up the combine or other harvesting equipment. Dried seeds will also last longer in storage and be more resistant to mold.
Sunflowers are a specialty crop, but have an important role to play in our food sector as a snack item, oil crop, and more. And they can be the perfect addition to a garden or floral arrangement. So enjoy the beauty and utility of this versatile flower!