Are Sunflowers Perennials?
The fast-growing sunflowers (Helianthus annuus) that produce tall stalks topped with large flower heads and seeds are annuals -- they germinate, grow, flower, drop seed and die all within one growing season. However, not all plants called sunflowers are annuals; some are perennials and resprout in spring after the winter frosts end. Perennial types regrow and bloom each year. All sunflowers are members of the daisy family, Asteraceae. Does this Spark an idea?
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Annual Sunflowers
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Annual sunflowers have origins across the United States, Mexico and Central America. The seeds are eaten by birds as well as humans as a nutritious snack. If sown, the seeds grow quickly in warm, frost-free conditions in a moist, fertile but well-drained soil. In the bright sunlight, the sunflower develops a main stalk that may or may not branch. The fuzzy leaves look like like hearts or fat ovals. Large, showy flowers form atop the main stalk or multiple branch tips. After flowering, seeds develop and the entire plant dies, shedding seeds to the ground.
Perennial Sunflowers
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Other plants in the same genus, Helianthus, are called sunflowers but persist as perennials. The dark-eyed sunflower (Helianthus atrorubens), thin-leaved sunflower (H. decapetalus), swamp sunflower (H. angustifolius), ashy sunflower (H. mollis) and willow-leaved sunflower (H. salicifolius) are examples of species that return year after year. The beach sunflower (H. debilis) is a short-lived perennial, sometimes an annual, depending on how well the deep taproot establishes in the sand and if the winter remains mild.
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Other Sunflowers
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The mountainous western parts of North America, plants in the genus Eriophyllum are often called woolly sunflowers. There are 12 species in the group, which vary as to being annual or perennial in life cycle. The Mexican sunflower (Tithonia rotundifolia) is an annual flower than produces orange to orange-red flowers that more closely resemble zinnia blossoms than annual sunflowers. The giant Mexican, Honduras or Bolivian sunflower (T. diversifolia) is a tropical shrub that grows 8 to 15 feet tall with many stems.
Insight
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Sunflowers that are sold in seed form, such as those packaged and sold at garden centers and displayed in flower seed shelves, are most likely annual plants. Sunflowers that persist as perennials or are shrubs are sold as small plants in containers filled with soil. When in doubt, read the plant label or seed packet for information. Otherwise, contact your county cooperative extension office or botanical garden horticulturists to answer questions about the sunflower plant you purchased or currently grow in the garden.
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