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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I am from Ohio and also planted the mammoth sunflowers around May 27th, for the 1st time ever. Around 75 plants. We were getting worried that they weren't going to bloom. But recently they started blooming. And they didn't all bloom at the same time, it was like a week between some of them. I have various size blooms on almost all now. I wish you luck and hope they bloom soon for you.
Thanks, wind storm came thru on the 24th and wiped out most of the plants as I didn't stake them. We will see what happens to the rest but I'm guessing phosphorus as mentioned below. I'll try again next year since the plants grew to such amazing heights.
Well, you've got the growth, so they must be reasonably happy where they are. We think that they got/are getting too little phosphorus. Did you test you soil? Did you fertilize, especially without having tested the soil? A test may have revealed a nutrient balance that fertilizer could have fixed, in the proper mixture.
Basic plant fertilizer mix usually consists of nitrogen (N, and the first "number" in the row of three numbers), phosphorus (P), and potassium (k).
Nitrogen helps plants grow quickly and have abundant foliage.
Phosphorus helps roots to be healthy and helps blooms to set.
Potassium aids in overall plant health.
It's probably too late in season to fertilize now. Get your soil tested early next season, before you plant. Often, local cooperative extension services do this, but you can also buy kits at garder and nursery stores.
When did you plant your seeds? I also planted a few mammoth the end of May and the first one just recently bloomed. Hopefully my others bloom soon. I believe they have a 75 day maturity. I hope this helps you a little.
I live at the mouth of the keys. It is August and it is hot. Bee friendly sent me some wild flower seeds. Two grew. One I have no clue what it is. It is tall and bushy. The other grey like crazy straight up. At 2 feet of course I staked it. I stake everything that I do not want to flop over. Now I noticed as the flowers (3) are showing their color. I live in an apartment and grow these flowers because the bee population is dying off. I have 2 pkg to plant. Is there a "time"? All we have is sun and humidity. Will they attract bees?
I live in Southern California. My sunflowers are in full bloom but will die in a month due to the heat and the end of summer. I was curious as to what are some flowers that I can plant that are seasonal and will bloom in the winter to replace the sunflowers? If you know any, it would be extremely helpful, thank you!
I had a great sunflower crop this season, but when cutting them down I noticed that there were larvae living inside the stems. They were completely hollow all the way up 6-10 inches beneath the blossoms... what is this and how can I avoid it in the future?
Sounds like sunflower maggots! A small fly lays its eggs on the stem which then hatch and burrow inside to eat the pith in the center of the stem. Since the pith doesn't have anything to do with the movement of nutrients within the plant, the maggots don't really do any harm. That is why you had a great crop of flowers despite the larvae.
What is the botanical name of sunflower
I planted "vanilla" sunflowers in my garden for the first time this year. It is now mid-August and the flowers have not bloomed yet, although there is a tiny bit of yellow just peeking out of the center buds. Is this normal? Or did I plant them too late? (I think it was very early June when I planted them). Thanks.
