How to Grow Sunflowers: The Complete Guide (2024)

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First and foremost, find a sunny spot! Sunflowers grow best in locations with direct sunlight (6 to 8 hours per day); they require long, warm summers to flower well. Shelter from strong winds—for example, along a fence or near a building—helps as they mature. Larger varieties may become top-heavy, and a strong wind can topplethem.

Choose a location with well-draining soil. The planting spot shouldn’t pool with water after it rains.Otherwise, sunflowers aren’t too picky about soil, but the soil shouldn’t be too compacted for the best results. They have long tap roots that need to stretch out; in preparing a bed,dig down or till 2 feet in depth and about 3 feet across. They’re not too fussy when it comes to soil pH, either. Sunflowers thrive in slightly acidic to somewhat alkaline soil (pH 6.0 to7.5).

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 yoursoil.

Plant sunflowers in a spot sheltered from strong winds, perhaps along a fence or building. Larger varieties may become top-heavy, and a strong wind can bedevastating.

Before choosing a planting site, decide whether or not you want to grow asunflower tower—a fun project forkids!

When to PlantSunflowers

• It’s best to sow sunflower seeds directly into the garden (or outdoor containers) after the danger of spring frost has passed, anytime after soils have warmed to at least50°F(10°C).
• In the northern halfof the U.S. and in Canada, this will fall betweenApriland mid-June. In the South, this will probably occur in mid-March or earlyApril.
• Sunflowers dislike having their roots disturbed, so we recommend direct sowing instead oftransplanting.

Planting SunflowerSeeds

• Sunflowers should be planted 1 to 1½inches deep andabout 6 inches apart after the soil has thoroughly warmed. If you wish, you can plant multiple seeds and thin them to the strongest contenders when the plants are six inchestall.
• 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 closertogether.)
• A light application of fertilizer mixed in at planting time will encourage strong root growth to protect them from blowing over in thewind.
• Experiment with plantings staggered over 5 to 6 weeks to keep enjoying continuousblooms.
• If you see birds scratching around for the seeds, spread netting over the planted area until the seeds germinate. See more ways to keep birds away from your garden.

Check out this video to learn how to plantsunflowers:

• While the plant is small, water around the roots, about 3 to4 inchesfrom the plant. To protect the plant, it may help to put snail or slug bait around thestem.
• 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 ofwater.
• 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 nearthe plant’s base; it may help to build a moat in a circle around the plant about 18 inchesout.
• 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 oftime.

Everyone is familiar with those huge sunflowers that grow on towering eight-foot-tall stalks. Butdid you know some varieties top off at a modest 15 inches? Sunflowers are a diversebunch!

• The towering ‘Mammoth’ variety is the traditional giant sunflower, sometimes growing to over 12 feet tall.Its seeds are excellent for snacks and for feeding thebirds,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 feettall.
• ’SunrichGold’: An excellent flower for bouquets and arrangements, thissunflower grows to be about 5 feet tall and produces a single4- to 6-inch flower. The big, no-mess, pollenless flowers have rich, golden-yellow rays and green-yellow centers. This variety is wonderful forarrangements.
• ’Teddy Bear’:Just 2to 3 feet tall, this small sunflower is perfect for small gardens and containers. The fluffy, deep-gold, 5-inch blossoms on branching stems last for days in avase.

Cutting Sunflowers forBouquets

• For indoor bouquets, cut the main stem just before its flower bud has a chance to open to encourage sideblooms.
• Cut stems early in the morning. Harvesting flowers during the middle of the day may lead to flowerwilting.
• Strip stems of all leaves except for those closest to the flower head. Recut bottoms of stems at a 45-degreeangle.
• Handle sunflowers gently. The flowers should last at least a week in water at roomtemperature.
• Arrange sunflowers in tall containers that provide good support for their heavy heads, and change the water every day to keep themfresh.

Harvesting SunflowerSeeds

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

• 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 somewhatloose.
• With sharp scissors or pruners, cut the head off the plant (about 6inches below the flower head). Place in a container to catch looseseeds.
• Lie the sunflower head on a flat, clean surface and grab a bowl to hold theseeds.
• To remove the seeds, 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 washingclothes.
• 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 thebirds.
• Alternatively, you can cut the flower head early and hang the heads upside down until theseeds are dry; hang indoors or in a place that’s safe from birds andmice.
• Rinse sunflower seeds before laying out to dry for several hours orovernight.
• If you’re saving seeds to replant, store them in an airtight container in a cool, dry place until you are ready toplant.

Read our complete article on harvesting sunflower seeds here.

Catherine Boeckmann