Sunflowers

How to Plant, Grow, and Care for Sunflowers

Sunflowers
Pixabay

Sunflowers say “summer” like no other plant. American natives, sunflowers are grown for beauty and harvested for seed.

An annual plant, sunflowers have big, daisy-like flower faces of bright yellow petals (and occasionally red) and brown centers that ripen into heavy heads filled with seeds.

Tall and coarse, the plants have creeping or tuberous roots and large, bristly leaves. Some sunflowers grow to over 16 feet in height, though there are also varieties today that have been developed for small spaces and containers.

Most sunflowers are remarkably tough and easy to grow as long as the soil is not waterlogged. Most are heat- and drought-tolerant. They make excellent cut flowers and many are attractive to bees and birds.

Learn more about why you should start growing these happy flowers in your garden.

Planting

  • Sunflowers grow best in locations with direct sunlight (6 to 8 hours per day); they prefer long, hot summers to flower well.
  • Sunflowers have long tap roots that need to stretch out, so the plants prefer well-dug, loose, well-draining soil; in preparing a bed, dig down 2 feet in depth and about 3 feet across to ensure the soil isn’t too compact.
  • Find a well-drained location, and prepare your soil by digging an area of about 2-3 feet in circumference to a depth of about 2 feet.
  • Though they’re not too fussy, sunflowers thrive in slightly acidic to somewhat alkaline soil (pH 6.0 to 7.5).
  • Sunflowers are heavy feeders so the soil needs to be nutrient-rich with organic matter or composted (aged) manure. Or, work in a slow release granular fertilizer 8 inches deep into your soil.
  • If possible, put seeds in a spot that is sheltered from strong winds, perhaps along a fence or near a building.
  • Before planting, decide whether or not you want to grow a fun sunflower tower.

Sunflowers

Planting Sunflower Seeds

  • It’s best to sow sunflower seeds directly into the soil after the danger of spring frost is past. Ideally, the soil temperature has reached 55 to 60 degrees F.
  • Give plants plenty of room, especially for low-growing varieties that will branch out. Make rows about 30 inches apart. (For very small varieties, plant closer together.)
  • Plant the large seeds no more than 1 inch deep about 6 inches apart after it has thoroughly warmed, from mid-April to late May. You can plant multiple seeds and thin them to the strongest contenders when the plants are six inches tall.
  • A light application of fertilizer mixed in at planting time will encourage strong root growth to protect them from blowing over in the wind.
  • Experiment with plantings staggered over 5 to 6 weeks to keep enjoying continuous blooms.
  • If you see birds scratching around for the seeds, spread netting over the planted area until seeds germinate. See more ways to keep birds away from your garden.

Care

  • While the plant is small, water around the root zone, about 3 to 4 in. from the plant. To protect the plant, it may help to put snail or slug bait around the stem.
  • Once the plant is established, water deeply though infrequently to encourage deep rooting. Unless the weather is exceptionally wet or dry, water once a week with several gallons of water.
  • Feed plants only sparingly; overfertilization can cause stems to break in the fall. You can add diluted fertilizer into the water, though avoid getting the fertilizer near the plant’s base; it may help to build a moat in a circle around the plant about 18 inches out.
  • Tall species and cultivars require support. Bamboo stakes are a good choice for any plant that has a strong, single stem and needs support for a short period of time.

Pests/Diseases

  • Birds and squirrels will show interest in the seeds. If you plan to use the seeds, deter critters with barrier devices. As seed heads mature and flowers droop, you can cover each one with white polyspun garden fleece.
  • If you have deer, keep them at bay with a tall wire barrier.
  • Sunflowers are relatively insect-free. A small gray moth sometimes lays its eggs in the blossoms. Pick the worms from the plants.
  • Downy mildew, rust, and powdery mildew can also affect the plants. If fungal diseases are spotted early, spray with a general garden fungicide.

Harvest/Storage

  • For indoor bouquets, cut the main stem just before its flower bud has a chance to open to encourage side blooms.
  • Cut stems early in the morning. Harvesting flowers during middle of the day may lead to flower wilting. 
  • Handle sunflowers gently. The flowers should last at least a week in water at room temperature.
  • Arrange sunflowers in tall containers that provide good support for their heavy heads, and change the water every day to keep them fresh.

Dried sunflower heads

Harvesting Sunflower Seeds

  • To harvest seeds, keep an eye out for ripeness. The back of the flower head will turn from green to yellow and the bracts will begin to dry and turn brown; this happens about 30 to 45 days after bloom and seed moisture is about 35%. Generally, when the head turns brown on the back, seeds are ready for harvest.
  • Cut the head off the plant (about 4 inches below the flower head) and remove the seeds with your fingers or a fork.
  • To protect the seeds from birds, you can cover the flowers with a light fabric (such as cheesecloth) and a rubber band.
  • Alternatively, you can cut the flower head early and hang the heads upside down until the seeds are dry; hang indoors or in a place that’s safe from birds and mice.

Recommended Varieties

Wit & Wisdom

  • Need a bird seeder? Save whole, dry sunflower heads and set them out in winter.
  • Save thick sunflower stems and dry them for winter kindling.
  • Interesting Fact: An anonymous buyer paid over $39 million in 1987 for Vincent van Gogh’s Sunflowers.
  • Kansas is “The Sunflower State.”

Here and yonder, high and low,
Goldenrod and sunflowers glow.

–Robert Kelley Weeks (1840–76)

Cooking Notes

  • Some varieties produce small black seeds that are used in cooking oil, margarine, cosmetics, and animal feed; they are the best sunflower seeds for attracting the greatest variety of songbirds.
  • The bigger, striped seeds are grown for snacking and as an ingredient in bread and health foods. They, too, are used for feeding birds, especially larger species, such as jays and mourning doves.
  • For eating, the seeds must be dried on the plants. Rub the seeds off and soak them overnight in a gallon of water to which a cup of salt has been added, then dry them again in an oven at 250 degrees F for 4 to 5 hours. Store them in an airtight container.
  • One way to remove them is to rub the head of the sunflower across an old washboard or something similar. Just grip the head and rub it across the board as if you were washing clothes.

Botanical Name: 

Helianthus

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