Sunflowers – Symbols of Summer

Sunflowers are one of our iconic symbols of summer.  Their bright yellow flowers resemble the sun, hence their common name.  The scientific name (Helianthus) comes from Helios meaning “sun” and anthos meaning “flower”.  Sunflowers also get their name from the plant’s ability to follow or track the sun, a phenomenon known as heliotropism.

As with many native plants, Native Americans have utilized sunflowers for generations.  Seeds have been 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 the sunflower’s beauty and versatility, seeds were quickly sent to European countries from the New World.   For years sunflowers were grown mainly as “exotics” or “curiosities”.  It wasn’t until the 1950’s and 1960’s 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.  They are also a good source of vitamins, minerals, protein, starch, and calories.  Hybrid sunflowers are the most common 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, 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 foot to over 8 feet.

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

Giant cultivars grow to a height of 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:

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

Cultivars that are 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:

The fourth group, the Pollenless cultivars, is used primarily as cut flowers or garden plants.  Pollen free types don’t 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:

Growing Sunflowers at Home

True to their name, sunflowers need sun – full sun – for best performance.  They thrive in 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 development.  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 and providing good air circulation between plants.  Bird deterrence is more difficult and may require netting, scare tactics, or other “creative approaches” to prevent damage.

Sunflower seeds are typically direct seeded (1-2 inches deep) outdoors in spring.  Seeds germinate within 7-10 days.  Seeds can be planted in early May in central Iowa as seedling can tolerate a light frost.  Seeds can also be started indoors in biodegradable pots/containers.  Biodegradable containers such as peat pots or newspaper containers are best since seedlings often perform poorly when disturbed by transplanting.  The entire peat-pot can be planted directly in the planting hole without disturbing the seedling roots.  When using biodegradable containers it is important 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.  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 heads 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 plant in your garden today.