How to Plant, Grow, and Care For Sunflowers
Are you looking to plant some sunflowers in your garden or yard, but aren't sure where to start? The good news is sunflowers are relatively easy to plant. They are great for novice gardeners, and more advanced gardeners alike. In this article, gardening and flower expert Taylor Sievers walks through how to effectively plant, grow, and care for sunflowers.
Few flowers come to mind that can have as great of an impact as a bright, cheerful, show-stopping sunflower. As a farmer-florist, I can attest to the fact that there’s just something special about a bouquet of fresh-cut flowers with a sunflower peeking out.
There are over 150 species of sunflowers, but the common sunflower you see growing in most gardens is the giant sunflower Helianthus annuus. These beautiful blooms—along with zinnias, dandelions, lettuce, and daisies—are members of the Asteraceae family. This family was formerly known as Compositae because of the family’s characteristic of composite flowers.
In this article, we examine the Sunflower in all its glory. You’ll learn about sunflower history, how to grow them, the best way to care for them, as well as some tips, and tricks to get you started on your next harvest. Let’s jump in!
- 1 About Sunflowers
- 2 History
- 3 Cultivation
- 4 Propagation
- 5 When to Plant
- 6 How to Grow
- 7 When and How to Harvest
- 8 Sunflower Varieties
- 9 Pest Prevention
- 10 Preservation
- 11 Plant Uses
- 12 Frequently Asked Questions
- 13 Final Thoughts
Sunflower Plant Overview
Plant Type Annual
Native Area North America
Hardiness Zone USDA 2-11
Exposure Full Sun
Maturity Date 120 Days to Seed; 90 Days to Flower
Growth Rate Fast
Plant Spacing 4-18 inches
Planting Depth 1-2 inches
Height 2-12 feet
Watering Requirements Moderate to High
Pests and Diseases Downy Mildew, Moth Larvae
Tolerance Temperate Climates
Soil Type Sandy to Clay
Attracts Bees, Birds
Plant With Squash, Cucumbers, Lettuce
Don’t Plant With Plants That Require Full Sun
Composite flowers are actually multiple tiny flowers (florets) that together appear to make one single flower. This means that the flower head we call a “sunflower” is actually made up of hundreds of tiny flowers! The usually dark center of the flower is made up of several disk florets. They will eventually become pollinated and produce sunflower seeds. The outer ring of the flower head (the petals) are actually ray flowers, which are sterile flowers whose purposes are for attracting pollinator insects.
True to their name, the sunflower is also a “sun tracker.” Botanically speaking, we call the characteristic of a plant following the sun heliotropism. This allows for the plant to receive up to 10 percent more sunlight! More sunlight interception means more plant growth, which is likely why these plants are such fast growers.
Sunflowers are not only beautiful, but they have a rich history and many uses. Read on to learn more about how to grow these charming plants I like to affectionately call “sunnies!”
Sunflowers are one of the few plants that are native and were domesticated in North America. Most crop species were domesticated in areas like the fertile crescent (ancient Mesopotamia), Asia, South America, and Central America, which makes the domestication of the sunflower so unique.
Prehistoric sunflowers were much smaller than their modern descendants, but Native Americans utilized these small sunflowers for food, fiber, and fuel. The seeds were collected for eating, and the stalks were utilized for construction and burning. The petals were used as pigments for dyes, and other parts of the plant were used for medicinal purposes.
The spread of sunflowers across North America was likely inadvertent, with seeds being dropped accidentally at various Native American campsites. Archaeological evidence suggests that in eastern North America, sunflowers were domesticated sometime before 1500 B.C. and that by 500 B.C. At that time, this plant was widely cultivated. The eastern North American cultivation history of sunflower also lines up with the American southwest and Mexican widespread cultivation of sunflower.
Mutations and selections by humans over time changed the sunflower. These plants were bred to produce larger heads and, most importantly, larger seeds! Seeds of domesticated sunflowers became four times larger than the sunflower’s ancestral wild counterpart.
Use in Early America & Europe
When the Europeans “discovered” the Americas, maize (corn) had become the major agricultural crop grown by Native Americans. However, sunflowers had been the major agricultural crop in the eastern woodlands 700 to 1,000 years prior to the arrival of maize from Mexico and Central America!
In the 1805 journal of Lewis and Clark, a meal is recorded, made by Native Americans for the explorers, that was considered “a very palatable meal.” The dish was made with ground sunflower seed meal mixed with grease and cooked meat that was then made into a dough.
Around 1510, the Spaniards brought the first sunflower seeds to Europe. The plant was never thought of for edible uses until it made its way to Russia in the 1800s. By 1860, Russia had begun breeding sunflowers to increase the oil extraction content. The Russians are the people responsible for increasing sunflower seed oil content from 28 to 50 percent by the late 1940s!
These new higher oil content varieties were reintroduced into the United States after World War II. This led to a rekindled interest in the crop. Sunflower breeding in the 20th century also led to earlier maturing varieties, higher yields, and semi-dwarf varieties. All of these improved traits would lead to global-scale production of the sunflower.
Production of sunflowers in the United States ramped up in the Great Plains states after the reintroduction of new varieties. Sunflowers were cultivated as an oil crop, birdseed crop, and for human snack food. Sunflower acreage in the U.S. peaked in the 1970s, falling shortly after due to crop prices and pest problems. Production has begun to slowly ramp back up since then.
Today, sunflowers are grown to produce vegetable oil, snacks, birdseed, and livestock feed. Livestock feed is derived from parts of the sunflower seed that are left after the oil extraction process, such as sunflower meal or sunflower hulls.
Sunflower meal has 28 to 32 percent protein and therefore is an adequate feed source. If the seeds are not dehulled or partially dehulled, then the total protein percentage will drop. Sunflower hulls are sometimes used as roughage to feed livestock, but due to transportation costs, the hulls are usually burned at the oil extraction facility.
Sunflowers can also be cut for silage, with the crude protein level of sunflower silage being higher than corn silage but lower than alfalfa hay. Silage is created when a crop is cut at its “green” stage and subjected to anaerobic (without oxygen) conditions. Today, this fermentation process is usually conducted via the use of silos or plastic bags. Sunflowers should be cut for silage when half the flower head has immature seeds. The plant should be allowed to wilt and dry out before being ensiled. Silage is used as livestock feed, particularly for cattle.
Sunflower oil can also be used for industrial purposes, but because it is also considered a food oil it is much higher in price than petroleum feedstocks or oil-derived products. Sunflower hulls have also been marketed as poultry litter, fireplace logs, and other high-fiber specialty products.
Sunflowers are also grown as a specialty cut flower for floral arrangements and weddings.
First off, if you’re looking for an easy and beautiful flower to grow in your garden, the sunflower is it! The seeds are usually pretty cheap and they can be easily found at your local grocery or hardware store. And speaking of sunflower seed—seed is the best way to propagate sunflowers!
If you’ve ever purchased a bag of sunflower seeds, you’re probably familiar with the black-and-white or gray-and-white outer shell of the sunflower seed. However, sunflower seeds can also be all black, too! Some are small and some are bigger―it just depends on the variety.
Sunflowers can be started indoors or planted directly into the garden. If starting indoors, sow the seeds about 4 to 6 weeks prior to your last estimated frost. Make sure your seeds are planted at a depth of 1 inch. A general rule of thumb for planting depth is to bury the seed at least 1 to 2 times the size of the seed.
Keep your pot or seed tray moist as the seeds begin to germinate. Once the seedlings emerge, make sure you water when the seed-starting mix starts to dry out.
Direct Sowing in the Garden
To sow seeds in the garden or landscape, use a triangular hoe or hand spade to create a furrow. Place seeds approximately 6 to 12 inches apart. Some professional cut flower growers like to plant their sunflowers as close as 1 to 2 inches apart because the sunflower heads will be smaller and better suited for bouquets.
If you want larger sunflower heads, then make sure to give your plants ample room, especially branching sunflowers (see Sunflower Varieties section below for more on branching vs. non-branching sunflowers). Cover the furrow with at least 1 to 2 inches of soil.
Some people have great luck with broadcasting sunflower seeds on the surface of their soil. Be aware that broadcasting seed usually results in lower germination rates, but nevertheless you’ll likely have at least a few plants pop up from your efforts! In fact, in some areas sunflowers can be considered weeds because of their ability to self-sow.
Many times I have left my sunflowers to go to seed, and in the spot I let them drop their seed I’ll have hundreds of seedlings pop up come springtime! Just remember that seeds from hybrid sunflowers will not look like the parent sunflower. They’ll likely serve their purpose in your garden no matter what they look like.
Some varieties have been bred for container gardening, so don’t rule out the thought of having cheerful sunnies in your patio pots! These are often best grown without fillers in their own large pot to accommodate their root system and prolific growth habit.
When to Plant
Sunflowers should be planted or transplanted after your last estimated frost in the spring. On occasion, there are some varieties that will survive a light frost, but it is best to avoid planting too early if possible.
Mature sunflowers can withstand temperatures of about 25 degrees Fahrenheit. Seeds can germinate when the soil temperature is as low as 46 degrees Fahrenheit. Sunflowers can be planted in successions until mid-summer in order to have a continuous supply of cheerful blooms!
I like to plant sunflowers every 1 to 3 weeks throughout the Summer for my cut flower garden. I usually stop planting sunflowers when I’ve reached the date that marks 6 weeks before my first estimated frost in the fall because the varieties I plant usually take 50 to 60 days to mature.
If you want to know when your last sunflower planting should be, look up your first estimated frost date in the fall and your sunflower variety’s average days until maturity. Then, using your average days until maturity, count backward from your first frost date and you’ll have a time period of when to plant your last succession of sunflowers!
How to Grow
As its name suggests, sunflowers should be planted in a site that receives full sun (6-8+ hours of direct sunlight per day). Sunflowers love soil that is rich in moisture and nitrogen but can be grown in almost any soil ranging from high sand to high clay content.
They prefer soil with a pH of 6.0 to 6.8. They are inefficient users of water and love water, but can withstand some drought. For these reasons, sunflowers can withstand a small amount of stress, but the most important time to keep your sunflowers stress-free is during the 20 days prior and the 20 days after flowering. Amending the soil with compost will help increase your organic matter content, and thus increase water holding capacity and the soil’s ability to retain nutrients.
Sunflower placement in the garden is important because most varieties will be several feet in height. Their height can be detrimental to neighboring plants that may require full sun to thrive.
Plant your sunflowers at the back of a garden or several feet away from shorter plants requiring full sun. You can use the height of your sunflowers as an advantage for plants that like partial sun. Living in the United States, I plant my sunflowers on the north end of my garden because most of my sunlight comes from the south during the Summer.
Water your sunflowers well at the beginning of their growth to promote strong root systems. Sunflowers will likely not need to be staked if they establish a strong root system. However, in very windy areas they may benefit from staking.
Before fertilizing, it is best to have a soil test so you know the fertility of your specific soil before amending it. Contact your local agricultural extension office or soil testing facility to find out how to take soil samples and where to send them.
Sunflowers can benefit from the application of a well-balanced fertilizer (i.e. a fertilizer with mostly equal parts nitrogen, phosphorus, and potassium). Examples of well-balanced fertilizers would be 10-10-10 or 20-20-20, and they can be mixed into the soil prior to planting when in granular form or mixed with water and applied using a hose or watering can.
Another alternative that is considered organic would be to use a mixture of fish emulsion and liquid seaweed. This can be applied every few weeks via a foliar application or applied with a watering can into the soil. Always follow the manufacturer’s instructions for mixing and application rates of fertilizers. Once your sunflowers take off they will likely not need to be fertilized.
Depending on the variety of sunflower you are growing, you may want to pinch your sunflower plant when it reaches at least 12 inches tall. Sunflowers that are considered branching will produce buds at leaf axils which will develop into flowers, resulting in a single plant with several blooming flowers.
Branching sunflowers can be pinched just above a set of leaves when small, which will induce the plant to produce several flowers on long, straight stems suitable for cutting. If left alone, branching sunflowers will produce several branches also, but they will often be shorter and not suitable for cutting due to their short stem length. This is really up to the home gardener and what their purposes for their sunflower plant will be!
Non-branching sunflowers have been bred specifically to produce one uniform and large flower head. On occasion, there will be buds that form at leaf axils that will produce small flowers, but if you pinch your nonbranching sunflower then you will be missing out on the big, beautiful sunflower head that you were likely hoping to have!
Check your seed catalog or seed company’s website to make sure you know what type of sunflower you are planting. When in doubt, don’t pinch.
When and How to Harvest
You will harvest your sunflowers at different stages depending on what your purposes for planting them were! If you are wishing to use them as a cut flowers, you can cut them any time after the petals have started to lift from the center disk.
The sunflower will continue to open in a vase after being cut. Cut at the base of the stem of the flower on a branching sunflower or at any length you’d like your stem to be if it is a non-branching sunflower. I cut stems as long as I can so that I can trim them to the correct length for my vase when I’m arranging them in a flower arrangement.
If you wish to harvest your sunflowers for seeds, wait until the flower has faded. Usually, the back of the flower head will turn yellow or brown when the seeds are fully mature and the flower head is dry. You’ll notice the head begin to droop slightly and the center disk becomes more rounded and full as the seeds have developed.
Make sure you collect the seeds before the birds get to them if you’re wanting to save them! The easiest way I’ve found to collect seeds is to cut the head off and use my fingers to wiggle the seeds out into a bowl or onto a cloth.
If you would like to use sunflower seeds to feed birds, a neat idea is to cut two or three sunflower heads after the seeds have developed and bundle them together. Hang this bundle upside down on a porch post or anywhere you like to enjoy your birdwatching. The sunflower heads become dried decor and bird feeders all-in-one! 45 species of birds are known for eating sunflower seeds.
Varieties are lumped into several categories that include giant, dwarf, pollen-less, branching, and non-branching. Branching sunflowers will produce several sunflower heads per one plant, which is why these are a favorite in the garden!
Non-branching sunflowers are (usually hybrid) sunflowers that have been bred specifically for their large, uniform heads and early maturity dates. They are a favorite of cut flower farms and oilseed farmers alike.
Some varieties are even pollenless, so if you’re cutting these sunflowers for a bouquet you won’t have all that yellow pollen dropping on your white tablecloth. Your seed catalog or seed company will usually tell you whether the variety is branching or non-branching.
- Sonja – Tangerine orange flowers with dark disks, ideal for cutting, approximately 42” height.
- Shock o’ Lat – F1 hybrid sunflower that reaches 6 feet tall, pollen-free flowers have deep chocolate petals with bright yellow tips, excellent for cut flowers.
- The Joker – F1 hybrid sunflower that reaches 6 feet tall with interesting semidouble crested flowers that are 4 inches in diameter, flowers are bicolor mahogany-red with gold tips and pollen-free. This plant has a short maturity of 55 days.
- Teddy Bear – Dwarf habit at 16 inches tall, fluffy double flowers that are golden-yellow.
- Moulin Rouge or Rouge Royale – Pollen-free sunflower with exquisite dark red flowers.
- Procut Series – This series is pollen-free, day-neutral, early maturing (55 days), and is excellent for cut flower production with 3 to 4 inch uniform flowers. Colors include orange, lemon, gold, bicolor, plum, red, white, and more. A few varieties have light-colored disks rather than brown.
- Sunrich Series – This series tops out around 3 to 4 feet and is pollen-free with midsize 5 to 6 inch blooms. Flowers mature within 55 to 70 days of sowing. Colors are orange, lime, lemon, and gold (with a green center).
- Double Quick – 5 foot tall with double 5 inch sunburst flower that is distinctly green-centered. Pollen-free variety maturing around 65 days from sowing.
- Vincent’s Choice – 5 to 6 foot tall variety with strongly overlapping orange petals that make it appear to be a semidouble flower. Excellent cut flower for shipping and arranging.
- Mongolian Giant – Plant reaches 11 feet tall with large 1 ½ inch seeds. Flowers can be up to 18 inches across.
- Mammoth Grey Stripe – Plant reaches 8 to 12 feet tall with flowers up to 20 inches across. Bright yellow petals and tasty seeds.
- Sunbuzz – This dwarf variety only reaches 8 to 12 inches tall with a plant spread of 12 to 20 inches. The flowers are pollen-free with bright yellow overlapping petals.
- Smiley – This variety reaches about 8 to 15 inches tall. It is a very early flowering variety (8 weeks from sowing to flower) that is pollen-free and extremely branching. The flowers are large, deep yellow, and they reach up to 4 to 6 inches in diameter.
Sunflowers can be severely affected by diseases and insect pests. There are a few cultural methods that will help reduce the incidence of disease and pest infestations in your garden that are talked about below.
Common Diseases of Sunflower
Most diseases that affect sunflowers are fungal and will affect the lower leaves of the plant first, so if the plants are mature when infected the disease may not be a problem. Sclerotinia stem rot (Verticillum dahliae) causes wilt soon after flowering and a light tan band at the base of the stem. Seeds and meat of the seeds will be discolored.
Rust (Pucchini helianthi) will cause rust-colored pustules on the leaves and black spots on the stems. Leaf spot will cause dead splotches on the leaves. Downy mildew (Plasmopara hastedi) causes cottony fungus growth on the undersides of the leaves and stunting and/or discoloration, while powdery mildew (Erysiphe cichoracearum) causes cottony fungus growth on the leaves often in late summer.
Utilizing crop rotation within your garden will help limit disease in your sunflowers. Crop rotation is a practice that involves rotating plants or families of plants throughout your garden to help prevent the buildup of disease or pest pressure.
Widening plant spacing will also help with diseases like powdery mildew, which likes moist conditions. Allowing more space between plants will increase airflow between plants to ensure rain or dew evaporates from the leaves quickly.
Watering your plants at the base of the stem rather than overhead watering will also help prevent disease incidence and spread, as well as planting in a well-drained site, as most disease spreads through interaction with water.
Planting disease-resistant varieties is also an excellent cultural practice. The seed catalog or seed company will usually have information on the diseases each variety may be resistant to.
Over time, plant breeders have selectively chosen plant varieties that appear to naturally resist certain diseases, and they use these plants when they cross varieties to create new varieties, resulting in vigorous, uniform, and disease-resistant offspring that can be planted by commercial cropping operations and home gardeners alike.
Common Pests of Sunflower
Larvae of the sunflower moth, banded sunflower moth, and sunflower bud moth feed on the flower heads, stems, and seeds of a sunflower. Often symptoms of larval feeding will be holes burrowed into the stems or heads of the sunflowers. This can cause distortion of the flower head or seed loss.
Sunflower midges cause the absence of ray flowers (petals) or cupping of the flower head. Sunflower maggots burrow into the stems. Beetle larvae are humpbacked, yellow larvae that cause severe defoliation. Cutworms and head clipping weevils can clip off flower heads or severely damage leaves.
Because the economic threshold levels for insecticide use on sunflowers have not been established and due to the probable killing of beneficial pollinator insects, it is not advised to spray insecticides on sunflowers.
If pest larvae or eggs are present on sunflower stalks and leaves, one option would be to pick them off the plant. Releasing beneficial insects into your garden that prey on caterpillars or eggs and crop rotation are two other ways to help reduce insect pressure buildup. Examples of beneficial insects are lady beetles, praying mantises, and lacewings.
Birds and deer are two non-insect pests of sunflowers. Birds like to feed on the sunflower seed, while deer like to feed on the immature sunflower plants. Use fencing or repellants to control deer feeding. Artificial owl decoys, spinners, and scarecrows will help prevent birds from feeding on the seed if your goal is to harvest the sunflower seeds for use.
To preserve sunflower seed for bird feeding or snacking, clip the flower heads at the appropriate harvest time and allow them to dry. Seeds should be free of moisture when put into storage. They should also be in a sealed container or paper bag in a cool, dry place.
If preserving the flower heads for winter bird-feeding, after drying the heads in a warm, ventilated space, simply place the flower heads in a paper bag. Store them in a dry place until you’re ready to put them out for birds to feed on.
Sunflowers can be cut for fresh or dried flower arrangements. Fresh sunflowers can be cut just as the petals begin to lift and open and stored in a cooler for storage longevity. Sunflower heads can also be air-dried by hanging the flower heads upside down in a warm, dry, well-ventilated space. However, the petals will shrink and become distorted.
Another option would be to bury the flower head in silica sand for a few weeks in a sealed container. The silica sand will absorb the moisture in the flower head. To harvest sunflowers for drying, make sure that the flower is fully open.
Commercially, sunflower seeds are used for oil, livestock feed, and human snack foods, as well as many other specialty uses. Historically, sunflowers were used by the Native Americans as food, fuel, and for construction purposes.
These plants are also celebrated for their big, beautiful blooms in the garden and in fresh floral arrangements. Sunflower fields are popular photo opportunities for photographers and agro-tourism farms. They attract birds and pollinator insects, so they are a great asset to a pollinator-friendly garden or vegetable garden.
Frequently Asked Questions
Why are my sunflower seeds not germinating?
Sunflower seeds are large seeds that need excellent seed-to-soil contact and high moisture to germinate. If you have planted your seeds too shallow then you may see some issues with germination rates.
Plant your seeds at least 1 to 2 inches deep and water routinely after planting to keep the area moist but not flooded. Sometimes rodents or birds will dig up sunflower seeds and eat them or even eat the small seedlings.
Check your garden for signs of rodents or birds. You may need to replant new seeds if this is the case. Using scare tactics like scarecrows and spinners will help deter birds.
Why do my sunflower heads face one direction?
Sunflowers are heliotropes (a.k.a. “sun trackers”), meaning their flower heads will follow the sun from east to west during the day and return to the east position in anticipation of the sunrise during the night. Tracking of the sun allows the plant to optimize up to 10 percent more sunlight interception, which improves plant performance and growth.
Once sunflowers have reached their final stage of flower development, they’ll remain facing east. Sunlight coming from the east helps to warm the flowers up sooner in the day, thus making the flowers more attractive for pollinators, like honeybees.
Why are the leaves turning brown and dropping off?
Sunflowers are susceptible to several diseases that can produce leaf spotting and browning of leaves. This is most often the case in areas that are wet, where the water can splash from the soil onto your plants, therefore transferring pathogens living in the soil to your plant.
Most sunflowers are fast-growing and though the bottom leaves may be diseased and dying, these symptoms will likely not affect the blooms. Pinching off diseased leaves and disposing of the residue via burning or burying can help prevent the spread and disease pressure for the following year.
Mulching your soil with straw or wood chips may help prevent soil from splashing onto your leaves during a rain or watering event.
What is a good dwarf variety of sunflower for planting in pots?
Sometimes you just want a little sunshine on your patio or deck! Dwarf varieties of sunflowers have become all-the-rage here lately. ‘Sunbuzz’ only reaches about 8 to 12 inches tall with a spread of 12 to 20 inches. This compact hybrid is pollen-free with bright yellow overlapping petals.
‘Smiley’ is another dwarf sunflower that reaches about 8 to 15 inches tall. It is a very early flowering variety (8 weeks from sowing to flower) that is pollen-free and extremely branching. The flowers are large and deep yellow and will reach up to 4 to 6 inches in diameter.
What does “day neutral” mean when talking about sunflowers?
Certain plants have an awareness of the time of the year, which is called photoperiodism. Plants can be placed into three different groups based on their response to photoperiod: 1) short day, 2) long day, and 3) day neutral. Photoperiod is the time of uninterrupted daylight that plants are exposed to within a 24 hour period.
Long day plants create blooms when the days are longer (>12 hours of sunlight) in the summer, and usually a sunflower is an example of a long day plant.
Some sunflower varieties have been bred to be less sensitive to photoperiod, so they are considered day neutral. As long as there are enough warm days for a day neutral plant, the plant will bloom at its approximate average days to flowering.
A photoperiod sensitive sunflower that is planted late in the season will bloom too soon, as the plant will often not be fully mature and therefore is either short or does not have much vegetative growth. Because the plant is sensitive to photoperiod, it is pushed into blooming due to the shortened days of the coming fall season.
Cheerful, strikingly beautiful, interesting, and a long history of use for human and livestock consumption, construction, and medicine―that’s the story of the sunflower. This is one plant you simply need to grow in your garden. These plants are easy to grow from seed, readily self-seed, and come in all sorts of colors and heights.
Use them in the background of a landscape, plant them in your personal cut flower garden, use a dwarf variety in a patio pot, add them into your pollinator-friendly garden or vegetable garden, or grow them to harvest your very own sunflower seeds for snacking! I promise―you won’t be disappointed by planting this American native known as the sunflower!