Growing Sunflowers

Posted On April 2, 2020

Sunflowers say “summer” like no other plant. Native to North America, sunflowers are heat-tolerant, resistant to pests, and simply beautiful. You can even harvest their edible seeds. Here’s how to grow them in your garden!

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.

Sunflowers are heliotropic, which means that they turn their flowers to follow the movement of the Sun across the sky.

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.

At the end of the season, it’s easy to harvest sunflower seeds for a tasty snack or for replanting.

Planting

Choosing and preparing a planting site

Sunflowers grow best in locations with direct sunlight (6 to 8 hours per day); they require 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.

Planting sunflower seeds

It’s best to sow sunflower seeds directly into the soil after the danger of spring frost has passed. Ideally, the soil temperature has reached 55 to 60 degrees F (13–16°C).
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 the soil has thoroughly warmed, from mid-April to late May in northern regions—earlier in southern areas. 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.

Care

Caring for sunflowers

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

Cutting sunflowers for bouquets

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.

Harvesting sunflower seeds

At the end of the season, harvest sunflower seeds for a tasty snack and or to replant or to feed the birds in the winter!

Let the flower dry on or off the stem until the back of the head turns brown, the foliage turns yellow, the petals die down, and the seeds look plump and somewhat loose.
With sharp scissors or pruners, cut the head off the plant (about 6 inches below the flower head). Place in a container to catch loose seeds.
Lie the sunflower head on a flat, clean surface and grab a bowl to hold the seeds.
To remove the seeds, simply rub your hand over the seeded area and pull them off the plant or you can use a fork. Another 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.
If you are going to harvest the seeds for roasting, you can cover the flowers with a light fabric (such as cheesecloth) and a rubber band to protect the heads from the birds.
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.
Rinse sunflower seeds before laying out to dry for several hours or overnight.
If you’re saving seeds to replant, store them in an airtight container in a cool, dry place until you are ready to plant.

Recommended Varieties

Everyone is familiar with the huge sunflowers that grow on towering eight-foot-tall stalks. But did you know that some varieties top off at a modest 15 inches?

The towering ‘Mammoth’ variety is the traditional giant sunflower, sometimes growing to more than 12 feet tall. Its seeds are excellent for snacks and bird feeders, too.
‘Autumn Beauty’: One of the most spectacular cultivars, the ‘Autumn Beauty’ has many 6-inch flowers in shades of yellow, bronze, and mahogany on branching stems up to 7 feet tall.
‘Sunrich Gold’: A great flower for bouquets and arrangements, this sunflower grows to be about 5 feet tall and produces a single 4- to 6-inch flower. The big, no-mess, pollenless flowers have rich, golden-yellow rays and green-yellow centers.
‘Teddy Bear’: Just 2 to 3 feet tall, this small sunflower is perfect for small gardens and containers. The fluffy, deep-gold, 5-inch blossoms last for days in a vase.

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