How to Grow Sunflowers From Seed

Sunflowers are warm-season annuals, so wait until the last spring frost has passed and the soil has warmed to at least 55F before sowing. For a long show of blooms, sow a fresh short row every 2 to 3 weeks from late spring into early summer. In hot southern states like Texas and Florida you can keep sowing through summer, while short-season northern gardens should get seed in the ground by early June so the giant types have time to finish.

Sunflowers dislike having their roots disturbed, so sow the seeds right where they will grow rather than transplanting. Plant them about one inch deep in loosened soil in the sunniest spot you have, spacing small types around 6 inches apart, standard types 12 inches, and giants 2 to 3 feet apart. Keep the soil evenly moist and seedlings appear in 7 to 14 days. Thin once they are a few inches tall so each plant has room.

Once established, sunflowers are tough and mostly want sun and space. Water deeply but less often to push roots down, and stake tall varieties in windy, exposed sites so the heavy heads do not topple. They are not heavy feeders, so go easy on nitrogen, which grows leaves at the expense of flowers. In the Midwest and Plains, birds and squirrels will find ripening heads fast, so cover the ones you want to save with mesh or a paper bag.

Sunflowers are a pollinator magnet, and their tall stems can shelter or shade smaller plants. These four make especially good companions, and you can add any of them in one click:

For cut flowers, snip stems in the morning just as the petals open and the back of the head is still green. For seeds, leave the heads on the plant until the back turns brown and papery and the seeds are plump and striped, then cut the head, dry it in an airy spot, and rub the seeds free. Beat the birds to it by covering ripening heads.

Sunflowers earn their keep in the garden and the kitchen. Cut the blooms for big, cheerful bouquets that last well in a vase, and leave a few heads standing in fall for goldfinches and chickadees. Harvest and roast the seeds for a snack, or press the black-oil types that birds love best. Even the tall stalks make a quick summer screen or a living support for climbing beans.

• Toppling in wind: tall and giant varieties get top-heavy, so stake them or plant against a fence in exposed sites.
• Birds and squirrels eating the heads: cover ripening seed heads with mesh or a paper bag once the petals drop.
• Few flowers, all leaves: usually too much nitrogen or too little sun. Ease off rich feed and give them full, all-day sun.
• Downy or powdery mildew on leaves: space plants for airflow, water at the base, and avoid wetting the foliage.