Common Sunflower, Beach Botany

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I always like to visit friends in LaBelle. It’s an excuse to go flower hunting. On the Fourth of July I was  hunting along the edge of a rural road when I spotted a Common Sunflower, Helianthus annuus. I knew right away what it was because it was on the cover of my biology book. Annuus is not native to Florida. Rather it is a large annual forb that grows natively in Europe as a crop for edible oil, fruits and black bird seeds. It is also cropped in the Western States. The plant I found had a single erect hairy stem and a height of 4 feet. Elliptic leaves are alternate on the stem. Leaf size is 10” long and 8” wide. Petioles are around 8” in length. Margins are heavily toothed.

At the tip of the stem is a single flower head with an 11” diameter. The inflorescence is called terminal. Yellow ray florets have fused petals and are sexually sterile. Each ray floret has five stamens at the edge of the disk. Ray florets are in two ranks  around the disk. Relatively large tubular disk florets are colored brown, reddish and green. The flower head is bent 90 degrees from the stem. Fruit occurs when disk florets give way to achenes (seed pod) each carrying one large black seed. Blooms summer and fall.

The plant must be a cultivar from a local nursery. What is interesting about annuus is that it is the largest of the herbaceous Asters. A height of 10’ is common. The tallest sunflower on record achieved 30’.