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Horticulture and Home Pest News
Horticulture & Home Pest News is filled with articles on current horticulture, plant care, pest management, and common household pests written by Iowa State University Extension specialists in the Departments of Entomology, Horticulture and Plant Pathology.

Sunflowers

This article was published originally on 7/27/2005

History

Sunflowers are one of our greatest American treasures. Their bright yellow flowers resemble the sun hence their common name. The scientific name (Helianthus) also means sun-like as Helios means "sun" and anthos means "flower". Sunflowers also get their name from following or tracking the sun, a phenomenon known as heliotropism.

Like many native plants, Native Americans have used sunflowers for generations. The seeds were used to make oil, flour/meal, butter, and even a coffee-like drink. A hair dye was also made from the oil extracted from the ground seeds. Other dyes and paints were made from seed hulls, flower petals, and pollen.

Because of its versatility and beauty, sunflower seeds were quickly sent to European countries from the New World. For several years they were grown mainly as "exotics" or "curiosities". It wasn't until the 1950s and 1960s that breeders in the former Soviet Union developed cultivars (varieties) popular in oilseed production.

Versatility

Today, sunflowers are grown for a variety of purposes including oil, bird seed, snacks, cut flowers, and, of course, beauty in the landscape. Sunflower oil and seeds are high in polyunsaturated fat but contain no cholesterol. They are also a good source of many vitamins, minerals, protein, starch, and calories. Hybrid sunflowers are the dominate cultivars in both commercial oilseed and ornamental plant production.

Variety of Flowers

While we commonly think of sunflowers as large plants with bright yellow flowers, the truth is that sunflowers are available in a wide range of flower colors, forms, and plant heights. Sunflowers can be yellow, cream, orange, rose, red, burgundy, and bicolor. Flowers can be as small as 3-4 inches in diameter or more than a foot across. Flowers can be single or double. Sunflower cultivars vary in height from 1 to 5 feet.

Sunflowers are typically classified into 4 distinct groups based on height or use.

The Giant cultivars ultimately reach 8 feet or more. These cultivars sometimes require staking due to the sheer size of the plants, flowers, and seed heads. Plants should be spaced about 2 feet apart for good air-circulation. Some popular cultivars are:

Cultivar 

Height 

Flower Color/Form 

Comments 

American Giant 14 feet Golden yellow/single 12 inch flowers
Cyclops 15 feet Golden yellow/single 14 inch flowers
Giganteus 10 feet Yellow/single 12 inch flowers
Kong 12 feet Golden yellow/single 4-6 inch flowers
Mammoth Russian 12 feet Bright yellow/single 12 inch flowers: heirloom
Paul Bunyan 13-15 feet Golden yellow/single

The Semi-dwarf cultivars are between 3-8 feet and typically don't require staking. These cultivars generally work well in the beds/borders of most home landscapes. Some popular cultivars are:

Cultivar 

Height 

Flower Color/Form 

Comments 

Cappucinno 6-7 feet Burgundy-red/single 5-6 inch flowers
Chianti 4-5 feet Burgundy/single 3-4 inch flowers
Italian White 5-7 feet Creamy white/single 4-5 inch flowers; heirloom
Jade 4-5 feet Lime-cream/single 4-5 inch flowers
Lemonade 5 feet Yellow-white bicolor/single 5 inch flowers
Ring of Fire 4-5 feet Red-yellow bicolor/single 6 inch flowers
Soraya 5-6 feet Orange/single 4-6 inch flowers; sturdy plants
Strawberry Blonde 6 feet Rose/single 5-6 inch flowers
Sungold 6-7 feet Yellow/double 10 inch flowers
Tangina 3-4 feet Orange/single 4 inch flowers
Valentine 5 feet Lemon yellow/single 6 inch flowers
Velvet Queen 4-5 feet Yellow-orange-red bicolor/ single 8 inch flowers

Those cultivars 3 feet or less are considered Dwarf types. They generally work well in front of beds/borders, in limited spaces, or in containers. Some popular cultivars are:

Cultivar 

Height 

Flower Color/Form 

Comments 

Elf 1-2 feet Golden yellow/single 4 inch flowers
Sundance Kid 2 feet Yellow-burgundy bicolor/double 5 inch flowers
Sunset 3 feet Burgundy w/yellow tips/single 6 inch flowers
Sunspot 2 feet Yellow/single 10 inch flowers
Teddy Bear 2-3 feet Yellow/double 5-6 inch flowers

Another group, the Pollenless cultivars, is used primarily as cut flowers or garden plants. Pollen free types do not contain any of the bright yellow pollen that can stain clothing. Heights range from 2 to 8 feet with a variety of flower colors and forms. Some popular cultivars are:

Cultivar  

Height  

Flower Color/Form  

Comments  

Bashful 3 feet Rosy-yellow/single 4 inch flowers
Claret 5-6 feet Burgundy/single 6 inch flowers
Double Dandy 2 feet Red/double
Full Sun 3-4 feet Golden/single 5-7 inch flowers
Joker 6-7 feet Yellow-red bicolor/single 6-8 inch flowers
Moonshadow 4 feet Creamy white/single 4 inch flowers
Munchkin 2 feet Yellow/single 3-4 inch flowers
Peach Passion 4 feet Peachy-yellow/single 3-4 inch flowers
Ruby Moon 5-6 feet Burgundy-white tips/single 5-10 inch flowers
Shamrock Shake 4 feet Lime-cream/single 3-4 inch flowers
Starburst Lemon Arora 4-6 feet Yellow/double 3-4 inch diameter

Growing Sunflowers at Home

True to their name, sunflowers need sun - full sun - for best performance. They also prefer fertile, well-drained soils. Once established, sunflowers are quite drought tolerant. However, for the best, "meatiest" seed, do not allow serious water stress during flowering and seed formation. They have few major insect or disease pests. Hungry birds and powdery mildew are the biggest problems. Mildew can be avoided by placing the plants in full sun. Bird deterrence is more difficult and may require "creative approaches" to prevent damage.

Sunflower seeds are typically direct seeded (1-2 inches deep) outdoors in spring. Seeds germinate within 1-2 weeks. Seedlings can resist mild frosts, so many can be planted in early May in central Iowa. Seeds can also be started indoors in biodegradable pots/containers. Biodegradable containers such as peat pots or newspaper containers are best since seedlings resent transplanting. This way the entire container can be planted directly in the planting hole without disturbing the seedling roots. One important consideration when using biodegradable containers is to remove any portion of the container that sticks above the soil surface as it will act like a "wick" and dry out the roots.

Regular watering may be required to get sunflowers established after germination. After establishment a mild fertilizer solution or a slow release fertilizer can be applied. Avoid high nitrogen fertilizers as they tend to promote vegetative growth and inhibit flowers.

Harvest

Sunflower seeds reach maturity 70-100 days after planting. Sunflower seed heads are ready to harvest when they face downward and the inner petals (flowers) can easily be rubbed off. By this time the outer ring of colorful petals is spent and the back of the seed head is a lemon yellow color. Check a few of the seed to make sure they are completely "filled". At this time the seed head can be removed, placed in paper bags or netted in cheesecloth, and hung in a dark, dry, well-ventilated location to continue the drying process. Within a couple of weeks, the seed should be ready for roasting or giving to the birds.

Enjoy this wonderful native American flower in your garden today.

Sunflowers
A mix of sunflower cultivars.
Ruby Moon sunflower
Ruby Moon sunflower.
Soraya sunflower
Soraya sunflower.
Starburst Arora sunflower
Starburst Arora sunflower
Valentine sunflower
Valentine sunflower
Year of Publication: 
2005
Issue: 
IC-493(18) -- July 27, 2005