Planting, Growing, and Caring for Sunflowers
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Planting
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 topple them.
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 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.
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 be devastating.
Before choosing a planting site, decide whether or not you want to grow a sunflower tower—a fun project for kids!
When to Plant Sunflowers
- 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 least 50°F (10°C).
- In the northern half of the U.S. and in Canada, this will fall between April and mid-June. In the South, this will probably occur in mid-March or early April.
- Sunflowers dislike having their roots disturbed, so we recommend direct sowing instead of transplanting.
Planting Sunflower Seeds
- Sunflowers should be planted 1 to 1½ inches deep and about 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 inches tall.
- 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.)
- 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 the seeds germinate. See more ways to keep birds away from your garden.
Check out this video to learn how to plant sunflowers:
Growing
- While the plant is small, water around the roots, about 3 to 4 inches 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.
Harvesting
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 the middle of the day may lead to flower wilting.
- Strip stems of all leaves except for those closest to the flower head. Recut bottoms of stems at a 45-degree angle.
- 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, 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.
Read our complete article on harvesting sunflower seeds here.
Recipes
Cooking Notes
Just one ounce of sunflower seeds contains about 6 grams of protein and 14 grams of oils. The fats are almost entirely unsaturated with 9g of polyunsaturated and 3g of monounsaturated fats per ounce (NSA). The oil is high in linoleic acid and is a good source of vitamin E.
- Some varieties produce small black seeds 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.
How to Roast Sunflower Seeds
Re-soak seeds overnight in salted water. Run through a strainer and dry on a layer of paper towels.
Bake for 25 to 30 minutes at 325 degrees on a baking sheet. Seeds should be spread out in a single layer. Stir frequently during the baking and remove seeds when they look slightly browned. Don’t burn!
That’s it! You can add some olive oil, salt, and spices to your roasted seeds if you wish.
Or, you can also make suet cakes for the winter birds! See how to make suet.
Catherine Boeckmann
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If they were moved from indoors directly to a sunny spot, they are likely suffering from the shock of too much light (and heat). Plants that are grown indoors need time to adjust to the intensity of the Sun’s rays outdoors, which is why hardening off seedlings is important. Additionally, when plants are transplanted, their roots are often damaged to some extent and need to settle in again. Before then, they are more vulnerable to stress from things like too much or too little water, or too much sunlight.
My husband wants to know if he could till the stems into the garden?
It depends on how big they are. If they’re from smaller, thinner sunflowers, then you could get away with tilling them into the garden and letting them compost on site. If they’re of the thicker variety, you’ll probably want to break them down yourself and compost them in a dedicated compost heap.
I planted several sunflowers this year. All of them grew to about 5-6' tall. Beautiful flowers! However, only half of the flowers had shells with seeds in them. The other half had the shells, but nothing inside. Any ideas to what was the problem??
This could be due to insufficient pollination or, if it’ was particularly dry in your area this summer, a lack of sufficient water. Additionally, some varieties are better suited to developing “meaty” seeds. Generally, the large, “mammoth” sunflowers have the best seeds.
This year is my first year growing sunflowers and I planted a whole variety of different kinds. About a third of the seeds I planted came up and are doing great! Most of my sunflowers respond heliotropically as you stated here, and have been blooming sporadically throughout the season. I love your idea about planting in rounds so they keep blooming through the fall (where I'm at they would probably be done by mid September). I did not do that this year, but probably will next year! Hoping to use seeds from this year's flowers to grow next year's :) Thanks for the good read and the insight!
The reason I am here reading up on how to grow these is because these and hemp are both very good at removing toxins from the land. If someone wants to grow organic food but their land tests positive for chemicals not allowed in organic food, they can grow sunflowers or hemp and they will pull a vast number of harmful chemicals out of the ground and store them. I would not consume the seeds without having them tested for the chemicals first, but I just thought people might want to know that these are not only beautiful but they can serve a real purpose in healing the land.
I am growing sunflowers and want to harvest and save the seeds for next year. If I cut the heads and put them in water inside, will they continue "growing" and developing seeds, or do I need to leave the heads on the plant until the season is over? It would be nice to have beautiful flowers in the house, but I don't want to sacrifice the seeds.
As per above, for indoor bouquets, cut the main stem just before its flower bud has a chance to open to encourage side blooms.
For seeds,
- 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.
We have an 18 footer that came up in the middle of the tomatoes this summer. I assume it was squirrel-planted. It towers over everything. I call it our personal jack and the beanstalk. had to support it with twine "guy wires" anchored to corners of the garden.
