Sunflowers have always been one of my top favorite blooming plants. The list of their attributes is long; they are cheerful and uplifting, long blooming, easy to grow, feed the birds, good for flower arranging, etc.
I could go on and on, but the most interesting and fascinating features are twofold: the blooms actually move to follow the sun from east to west across the sky, and the seeds are arranged in a Fibonacci Spiral to pack as many seeds as possible in a small space.
Facing the Sun-Heliotropism
The amazing sun-following trick makes these plants seem to possess some mystical powers. What’s really going on here is something called heliotropism, and lots of plants do it. But with a field of huge sunflowers in bloom, it is a sight to behold. Heliotropism means moving toward the sun. The puzzle with sunflowers is, why do the flowers need to face the sun?
The stems of all actively growing sunflower parts – flowers and leaves – grow to face the sun in order to maximize photosynthesis. During the day, the stems elongate on the side away from the sun, tilting leaves and immature flowers toward the sun throughout the day and ending up facing west at sunset. When there’s no light, the other side of the stem grows, pushing the leaves and flowers back to the east where they will be facing the sun at sunrise.
Growing leaves and immature flowers are green and full of chlorophyll and actively photosynthesizing. The younger sunflower has immature leaves along the stem facing the sun as well. The lower leaves on the younger sunflower, as well as all parts on the older sunflower have matured, and though they are generally facing up, they are not facing the sun. Once the flower matures and is not actively photosynthesizing, then it remains stationary and will hang with the weight of the growing seeds.
The Fibonacci Spiral is another fascinating attribute of the sunflower. The concept is named after a Middle Age Italian mathematician named Fibonacci who was considered to be one of the most brilliant mathematicians of his time. The principle underscores that mathematics is utilized in nature in every facet, especially in the design of nature.
The Fibonacci spiral or numbers are nature’s numbering system. It appears everywhere in nature, from the leaf arrangement in plants, to the pattern of the florets of a flower, the bracts of a pine cone, or the scales of a pineapple. It means that a plant or animal grows in the most efficient ways, maximizing the space for each leaf, or the average amount of light falling on each one. Even a tiny advantage would come to dominate over many generations. In the case of close-packed leaves in cabbages and succulents the correct arrangement may be crucial for availability of space.