Growing sunflowers (Helianthus annuus) are the current rage. Sunflowers are native to Central America and have been cultivated for thousands of years. Sunflowers are classified as annuals, living one growing season, and often returning the following spring from seeds dropped the previous fall. Some gardeners put out large beds to feed the birds.
Sunflowers come in many varieties, some 3-5 feet tall with yellow, cream, or red flowers; others 10 feet and more tall giants with sturdy stems and blooms nearly a foot across. Most varieties mature in 70 to 90 days or more. Read the seed package for plant heights and harvest time (ripening).
Sunflowers are easy to start from seed. Sow seeds 4-6 inches apart and cover them with plastic mesh or screen until several have poked their heads up (germinated). Otherwise, birds and animals may dig the seeds up. You can also start seeds in a small protected seedbed, seed flat, or pot and transplant each individually when they’re a few inches tall. For a head start on spring, you may opt to begin 2 to 3 weeks earlier indoors in individual peat pots. Sow 1 to 2 seeds per pot, and thin to one before planting outdoors after the spring frost period.
Sunflower plants grow well in average to rich soil. They grow best in full sun, but do tolerate light shade. They perform better in deep soil for roots to become firmly anchored to withstand strong winds and dry spells.
They do benefit from heavy feeding with 10-10-10 or an equivalent fertilizer at planting time and again 8-10 weeks later. Nitrogen (N) promotes plant growth and sturdiness. Adequate phosphorus (P) and potassium (K) in the soil increases flower bud numbers and bigger blooms.
Tall sunflowers serve as good companions interplanted with ground trailing cucumbers, melons, pumpkins, or squashes. Plant only 5-6 sunflowers per 100 square feet, so not to shade the vines below.
Insects and diseases are seldom problems, particularly on new ground. The birds and squirrels are primary invaders of a sunflower crop, all coming to feast on the delicious oily seeds.