Few flowers are as cheerful as sunflowers. With bright golden-yellow petals and stems as tall as 15 feet, sunflowers are stunning additions to any garden or yard. 

If you’re wondering how long it takes for sunflowers to grow, we spoke to two garden experts for the definitive answer.

How Long Does It Take to Grow Sunflowers?

It takes 70 to 100 days to grow sunflowers, from planting to full maturity, says Lindsey Chastain, a gardener and homesteader who publishes the blog Waddle and Cluck.

“Sunflowers love sun, so they will grow faster in full sun,” Chastain says. “You will start to see flowers around the 50 to 70 day mark.” 

Rachel McClure, a horticulturalist and Washoe County’s Master Gardener Coordinator, adds that some dwarf types of sunflowers can bloom in as little as 60 days, while the larger mammoth sunflowers can take the full 100 days to bloom.

“Planting multiple types of sunflowers can ensure a prolonged blooming season,” McClure says. “Depending on your purpose, you may choose to grow flowers for cut flowers, pollinators, or bird seed.”

9 Signs Sunflowers Are Ready for Harvest

Sunflowers provide numerous visual and textural cues when they are ready to be harvested. 

• The flower has a dry back.
• Back of the sunflower has turned from green to brown or yellow. 
• Petals have dried up and are beginning to fall off.
• Seeds are plump.
• Seeds are either solid black or have dark stripes, depending on variety.
• Seeds pop out when you run your hand or thumb over them.
• Birds and other pests are pecking at and eating the seeds. 
• The sunflower head is heavy enough to droop downwards.
• The flower is completely open. 

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Why Sunflowers Need to be Harvested on Time

It’s essential to harvest sunflowers at the right time, McClure says. Harvesting too early or too late can result in poor growth.

For cut sunflowers, waiting too long after the flower has fully bloomed for harvesting will shorten its lifespan in the cut arrangement. 

For seed sunflowers, waiting too long to harvest means seeds being lost to birds and other pests. If pests don’t get the seeds, they will rot on the stem.

Factors That Affect Growth Time

Factors like soil fertility, spacing, moisture, and most importantly, sun, can affect how long for sunflowers to grow and seed size. 

• Sun: Sunflowers need six to eight hours of full sun daily.
• Spacing: Maintain proper spacing of about 1 to 2 feet for larger flowers and about 6 inches for smaller flowers. If sunflowers are crowded, the faster growers can block the late bloomers from receiving enough sunlight.
• Soil: Provide sunflowers with well-draining soil that contains a good amount of organic materials. With a pH between 6.0 to 7.0, the soil must also be at least 45°F in spring.
• Pests: Pests such as birds, squirrels, and deer can pose a challenge during their early stages of development. Chickens, ducks, or geese can provide natural protection around your sunflowers. Or use netting to protect them until they are ready for harvest.
• Moisture: Sunflowers are sensitive to soil moisture, particularly during their early growth stages. So, they must be kept well-watered.
• Planting time: Plant sunflowers two to three weeks before the last expected frost date. They should be planted as early as March (in southern U.S.) and as late as mid-June (in New England or Upper Midwest). Planting too late means that the flowers may not be healthy and strong enough to survive the summer heat.

Tips for Growing Sunflowers

• Support sunflowers to prevent their fragile stems from breaking. Stake sunflowers against fences or with long bamboo stakes.
• Till the area where you want to plant sunflowers, and mix in some compost to produce good, rich, well-draining soil. “Sunflowers become more drought-tolerant as they grow,” Chastain says.
• For edible seeds, large-headed types of sunflowers are best, McClure says. “If space is limited, dwarf varieties that stay compact are ideal and can be grown in containers as well.”
• Chaos gardening makes the process of growing sunflowers even easier, says Chastain. “I actually grow my sunflowers through chaos gardening,” she says. “I just throw some seeds out near my pond, and they grow every year.”
• To grow cut sunflowers, choose branching varieties that produce multiple blooms with long stems, says McClure.