Growing Sunflowers and Their Varieties

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.

History

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.

Learn more about the history of the sunflower in this article: Sunflowers: From Native American Staple to Modern Garden Favorite.

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 dominant 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.

Giant Cultivars

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. 

Semi-Dwarf Cultivars

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. 

Dwarf Cultivars

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. 

Pollenless Cultivars

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. 

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" seeds 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.

Tall growing varieties should be thinned to stand 2 to 2 1/2 feet apart in the garden and staked to help support the seedhead under windy conditions. 

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 seeds 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.

More Information

• Perennial Sunflowers for the Home Landscape
• How to Care for Cut Flowers
• How to Harvest, Condition, and Care for Cut Flowers
• Growing and Selling Cut Flowers in Iowa
• Flowers and Their Meanings: The Language of Flowers