What To Know About Growing Sunflowers From Seeds

If you’re looking to start a flower garden, the classic sunflower is always a great addition. Sunflowers bring vibrant color to your garden and attract beautiful visitors like hummingbirds, bees and ladybugs. For many, sunflowers are also a symbol of happiness thanks to their bright yellow pedals and sun-like appearance. Up ahead, we’re sharing how to grow sunflowers from seeds and what to do to help them thrive.

Choosing the Best Type of Sunflowers for Your Yard

Sunflowers come in various heights, bloom sizes and colors, all easy to grow from seed. Some sunflowers to consider include:

• Mammoth Grey Stripe: The classic, with a big yellow flower on top of a nine-to-12-foot-tall stem.
• Teddy Bear: Grows only three to four feet tall, with big double flowers resembling pom-poms.
• Chocolate Cherry: Grows six to seven feet tall with dark reddish brown flowers.
• Sunray Yellow Hybrid: Great for containers, this tops out at 18 inches or so, with several branches and lots of blooms.
• Ring of Fire: Bi-colored petals are red closer to the center and yellow on the tips, on five-foot stems.

When choosing sunflower varieties for your garden, remember taller varieties may need to be staked.

Planting Sunflower Seeds

Sunflower seeds are readily available. You can pick up a packet of seeds for just a few dollars at most garden centers. I’ve even gotten free sunflower seeds from my local library’s seed library.

“Sunflowers are very easy to grow and don’t really need all that much care. All they need is a sunny spot, fertile soil, and regular water,” says gardening expert Annette Hird, “This is especially important if you intend to grow them in pots because these can dry out quickly during hot summer days.”

When To Plant Sunflower Seeds

Plant in the spring once your garden is frost-free. Sunflowers will not tolerate frost and germinate best in warmer soils, so don’t jump the gun.

In areas of the country that don’t get frost, sunflowers are still generally grown from spring through summer.

If you’re concerned you don’t have a long enough growing season for sunflowers to bloom, check the seed packet to see how long on average it takes that variety to flower. If the number of days is shorter than your growing season, start seeds indoors a few weeks before your frost-free date.

How To Plant Sunflower Seeds

Sowing seeds directly in the garden

Sunflowers don’t like to be disturbed, so it’s best to leave them where you sow them.

• Cultivate the soil a few inches deep and remove weeds.
• Sow seeds at the depth and spacing noted on the seed packet. If there are no instructions, plant about an inch deep.
• Sow two or three seeds together, then thin to one seedling once the second set of leaves develops. Be careful not to disturb the roots when removing the extra seedlings. (To prevent this, I cut off extra seedlings instead of pulling them out.)

Sowing seeds indoors

“You can start the seeds indoors. It’s a good idea to just put one seed into each peat pot [a biodegradable pot made of peat moss] so that you can then plant them outside without disturbing the taproot,” says Hird, “They need the taproot to support those tall stems. And make sure you harden off your young plants before putting them into the garden.”

Here’s how to start sunflower seeds indoors:

• Plant two or three seeds in biodegradable pots with a seed starting mix.
• Keep soil evenly moist until seeds germinate.
• Thin out to one seedling per pot once seedlings begin to develop a second set of leaves.
• Keep seedlings under lights or near a bright window to avoid getting too leggy.
• Harden off seedlings before planting them outside.
• Plant in full sun and space them as far apart as instructed on the seed packet.

Whether starting seeds indoors or directly in the garden, choose a location with well-drained soil and full sun. Tall sunflowers can create a lot of shade, so plant them on the north side of full-sun flower beds to avoid shading out other flowers.

Sunflower Care

Watering

Sunflowers grow well with about an inch of rain a week, from rain or supplemental watering.

Thinning

Overcrowded sunflowers won’t grow as well, so space seedlings out as directed on the packet. Some smaller sunflowers may grow well a foot apart. Larger sunflowers will need up to two feet between them.

Staking

“Taller sunflower varieties may benefit from staking because those seed-filled heads can get really heavy and cause the stems to bend over,” says Hird.

If you often experience strong winds or storms, consider staking taller varieties of sunflowers to give them extra support. Put stakes in place before planting to avoid disturbing the seedlings later. Tie stems to stakes for support.

Fertilizing

Sunflowers can benefit from additional fertilizer, especially if grown in a container. Use a general-purpose fertilizer and follow the instructions on the label.

Controlling pests and diseases

Sunflowers don’t get too many pests or diseases, though rabbits or birds may eat new seedlings as they emerge. If this is a problem in your garden, start seedlings indoors. Once planted in the garden, protect seedlings with a row covering until they’ve grown larger than the edible stage.

Harvesting Sunflower Seeds

You can harvest sunflower seeds for bird or squirrel feed, or to eat yourself. Although technically all sunflower seeds are edible, we mostly eat the seeds from Helianthus annuus, the common sunflower.

When the flower head droops and the back of the flower turns yellow, the seeds are usually dry enough to harvest. If you’re concerned about birds getting to the seeds first, cover the flower head with cheesecloth or a paper bag. Or cut the flowers off, leaving a one-foot stem, and hang them where they can finish drying.

Check your local cooperative extension service for instructions on how to roast sunflower seeds, or use this information from Kansas State Research and Extension.

FAQ

Do sunflowers need special soil?

According to Fontana Seeds, “The best soil for sunflowers is well-draining, fertile soil with a slightly acidic to neutral pH. Sunflowers thrive in soil that is loose, friable, and rich in organic matter. Sandy loam or loamy soil types are ideal.”

How tall will my sunflowers get?

Depending on the variety, sunflowers can grow anywhere from 1 to 2 feet tall up to an impressive 12 to 15 feet tall. Dwarf varieties won’t grow very tall, the Elf Sunflower for example only reaches about 16 inches. The tallest sunflower variety is the Mongolian Giant, which can grow up to 14 feet tall and form giant 16 to 18 inch flower heads.

About the Expert

• Annette Hird is the owner and author of Easy Urban Gardens. Hird has an Associate Diploma in Horticulture and is an urban gardening expert. She has worked as a professional propagator and managed, maintained and improved many urban and rural gardens.