Helianthus spp. (Asteraceae) - Sunflowers

Helianthus spp. (Asteraceae)

Sunflowers (Sunflower Family)

Origin: North America

What is a flower? A flower is a plant’s sexual organ, typically consisting of male and female parts and the calyx and corolla. Some blooms which we see and consider as a single flower are actually hundreds of smaller flowers tightly grouped together. These flower heads, termed “capitula” (sing. “capitulum) are often composed of central, densely packed “disc” flowers surrounded by a ring of what appear to be petals, but which are the “ray” flowers. The sunflower family is the classic example of this type of flower arrangement. This is why a single sunflower “bloom” will produce so many seeds. It is actually many flowers packed in a single head. Once the flowers are pollinated, the ray florets will fall off, and seed production will begin.

The sunflower is one of the most American flowers there is. They grow across the country in a broad spectrum of conditions, from the swamps of Florida, to the prairies of the heartland, and to the cold, dry mountains of Wyoming. The capitula typically face east, a result of heliotropism (following the sun) during their budding stage. Once the buds open the orientation remains fixed. Contrary to popular belief, they do not rotate through the day to capture the sun.

Selby Gardens has several species of Helianthus currently in bloom. The best place to see these is at the south end, in our wildflower garden, where we have three species blooming native to Florida . Helianthus debilis,or “beach sunflower,” is a dune stabilizer native to our sandy coasts. Extremely tolerant of drought, salt, and wind, these plants colonize areas of the beaches in which conditions are too harsh for other plants. This species is prostrate and spreads rapidly. Helianthus angustifolius, or “swamp sunflower,” is native to marshes, swamps, and wet pinelands in the interior of the state. This is a much more erect plant than debilis, reaching several feet tall. It is extremely tolerant of poor drainage and standing water. The final species, Helianthus radula, is native to wet flatwoods and pinelands in the central and northern parts of the state. Unlike typical sunflowers, H. radula completely lacks ray flowers, which means that to us it looks like an older, bloomed-out seedhead whose petals have fallen off. This species consists of a low-growing rosette of leaves with an erect stalk which holds the capitula. Come check out the variety that nature has to offer today at Marie Selby Botanical Gardens!