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Missouri Environment & Garden



AUTHOR

David Trinklein
University of Missouri
Division of Plant Sciences
(573) 882-9631
trinkleind@missouri.edu

Sunflowers

David Trinklein
University of Missouri
(573) 882-9631
trinkleind@missouri.edu

Published: August 1, 2008

sunflowers

The term ‘sunflower’ conjures up different images in the minds of people depending upon their background. To an agronomist it means a valuable alternative cash crop grown for its oil and feed content; to an ornithologist it means a staple in the diet of many birds and a good way to attract them into one’s back yard; to a horticulturist it means an attractive flowering plant that is easy to grow and adds ornamental value to gardens.

Late summer and early fall is the time of the year when sunflowers are at their full glory. Many roadsides and meadows in our state are ablaze in a sea of gold because of the annual appearance of the native sunflower. Cultivated sunflowers also are nice this time of the year and often dominate the garden this time of the year because of their size and affinity for warm temperatures.

The common name ‘sunflower’ is given to any of 67 species and sub-species of the genus Helianthus, which is a member of the Asteraceae family. Members of this family bear a compound inflorescence known as a “head”. The latter consists of a row(s) of petal-like ray florets that surround an inner tuft of disk florets. In the case of Helianthus heads range in size from several inches to over one foot in diameter.

Archeological findings suggest Native Americans began raising sunflowers for food and medicine as early as 2300 B.C. This predates the cultivation of important native crops such as corn, beans and squash, which is an indication of their importance. Sunflower seeds usually were roasted and ground into a fine meal for baking or thickening agent for stews. Alternatively, they were made into a “butter-like”substance which was used to form “seed balls” –a food source for traveling. Roasted sunflower hulls were made into a coffee-like beverage. Oil, extracted from sunflower seeds by boiling, provided Native Americans with cooking oil, hair tonic and treatment for a range of ailments from snake bite to sunstroke.

Colonists sent sunflower seed from the New World back to Europe where it mainly was treated as a novelty. Not until it managed to reach Russia was its food and oil value exploited. Russians are credited with some early improvements of this plant. It is no wonder, therefore, that one of the most popular, older cultivars for seed production carries the name ‘Mammoth Russian.’

As mentioned above, sunflower still plays an important role in the U.S. economy as an oil and seed crop. However, it is the ornamental value of this plant that is of greater interest to gardeners. Recent improvements to sunflower have made it increasing popular in beds and border throughout the Midwest.

Ornamental sunflowers can be divided into one of two types: annual or perennial. Many of our annual sunflowers today are members of the species Helianthus annus; others are hybrids. Those considered more ornate usually are shorter in stature (three to five feet) and produce somewhat smaller, vividly-colored flowers in greater abundance than those grown for seed. ‘Ring of Fire,’ ‘Sonja’ and ‘Soraya’ are three fairly recent introductions to the gardening world that typify today’s annual sunflower. All are short in stature and have brightly colored flowers four to five inches in diameter suffused with bronze, gold and yellow. Other popular cultivars include ‘Teddy Bear’ which bears fully double bright yellow flowers on plants that reach a mature height of only two feet, and ‘Ballard.’ The latter is perhaps the smallest sunflower available and has the added virtue of being pollen-free.

There also are perennial forms of sunflower available. Most are hybrids and go by the scientific name Helianthus x multiflorus. They tend to be robust growers and typically bear an abundance of golden-yellow flowers two to three inches in diameter mid-summer through fall.

sunflower

Double and semi-double cultivars (e.g., ‘Flore Pleno,’ ‘Loddon Gold’ and ‘Meteor’) are available.

Two commonly grown perennial species (non-hybrids) are Helianthus angustifolius (swamp sunflower) and Helianthus salicifolius (willowleaf sunflower).

It should be noted that a very similar perennial in appearance goes by the name of Heliopsis helianthoides (or sunflower heliopsis). There are several outstanding cultivars of this species (e.g. ‘Summer Sun’) which provide the look of perennial sunflowers and hence is often confused with them.

Whatever the type, annual or perennial, sunflowers are relatively easy to grow and do well under Missouri (Midwest) conditions. As their name implies, sunflowers need sun–a minimum of six hours per day should be provided. Additionally, they prefer a well-drained, slightly acidic soil. They tolerate heat and dry conditions quite well but do appreciate adequate amounts of water if it can be supplied. Avoid the temptation to fertilize heavily (especially with nitrogen) since this leads to excessive vegetative growth and poor flowering. Sunflowers are not without disease and insect pests but they rarely warrant control.

Annual sunflower is propagated from seed which usually is directly sown in the garden after the soil warms in the spring. For a head start consider planting seeds indoor in small pots about two weeks before the weather warms enough to set them out. Perennial types are propagated by division in the spring or fall.

Sunflowers, especially the newer, shorter cultivars make good additions to the border garden. The more dwarf cultivars can be a novel addition to containers. Additionally, sunflowers can be used in the cut flower garden. Since the advent of the newer, brightly-colored cultivars commercial production of cut sunflowers has become a cottage industry for a number of gardeners. Finally, sunflowers make ideal plants for children’s gardening projects. Their large seeds are easy to handle and their rapid rate of growth and ability to handle adverse conditions make success almost guaranteed.

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REVISED: September 30, 2015