Some similarities to : Perennial Sunflower but Perennial Sunflower is only half as tall, has much narrower leaves, fewer and wider outer petals, a paler-yellow flower less than half as large and a dis-proportionately smaller central floret area.

Uniquely identifiable characteristics.

Distinguishing Feature : The tallest yellow-flowered plant in the U.K. Specimens have been known to grow to a height of 8m, but this is very unusual, normal height being about 2m.

Grown mainly in gardens for show or competitions.

FATTY ACIDS Grown commercially to yield sunflower oil (which is obtained from the seeds) and is used in cooking. Sunflower oil has varying proportions of the fatty acids linoleic, oleic, stearic and palmitic acids, depending upon the type of Sunflower from which it is derived, with the most predominant first and the least dominant last. Linoleic (not to be confused with Linolenic Acid) is doubly unsaturated, oleic singly un-saturated. Both stearic and palmitic acids are saturated fats and attempts are made to minimise these when the seeds are to be used for producing healthy cooking oil. The first three fatty acids have 18 carbon atoms, Palmitic Acid has only 16.

A yellow dye used to be extracted from the ray florets.

HELIOTROPISM Sunflowers are heliotropic (pointing towards the sun and following its progress across the sky) only when in the bud stage and not when in flower. When they set flower they affix themselves to point in one direction only, usually towards the morning Sun. The seeds are thus protected from the full blaze of the midday sun. The heliotropic response is mediated by one of the plant hormones, Indole-3-Acetic Acid (aka 3-Indolylacetic Acid or IAA) which is a heteroauxin or plant growth regulator. Indole-3-Acetic Acid is a light sensitive hormone which causes the cell to grow in an asymmetric fashion, elongating it. It is this aligned elongation which causes the flower to turn, nominally towards the source of the strong light, the sun. It seems that another auxin, Indole-3-acetonitrile (aka 3-Indolylacetonitrile or IAN), which has an inhibitory effect on asymmetrical cell growth may also be involved.

Famous for displaying Fibonacci spirals, where there are typically 34 seeds in the spiral in one direction, and 55 seeds in the other direction, both Fibonacci numbers. The Fibonacci mathematical sequence begins with the numbers 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89...

Annual Sunflower contains the toxic Sesquiterpene Lactone Niveusin A (as well as seven more toxic Niveusin A derivatives) which are contained in and around the trichomes present on both leaves and stem. These trichomes release the toxins when handled, and can result in dermatitis, which has been known of for centuries regarding Annual Sunflowers.

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