I was wandering around the garden this morning, taking snapshots of this, that and everything. What caught my attention today were the sunflowers; all cheerfully bobbing their giant heads in the breeze and looking to warm their faces in the morning sunlight.
I noticed several different varieties . . . and then I got curious. I don’t really know a lot about sunflowers other than that they’re pretty and the have yummy seeds.
I found out some interesting things in my research. A sunflower isn’t just one flower but a head with a lot of flowers – florets - crowding together – technically known as a composite flower. The outer flowers make up the larger petals and can be a variety of colors – yellow, orange, variegated, etc. The little florets in the center of the head are called disc florets. They are the ones that mature into seeds.
But wait . . . there’s more!
The disc florets in the center part of the head are arranged in a spiral pattern. Typically each floret is oriented toward the next by approximately the golden angle, 137.5°, producing a pattern of interconnecting spirals where the number of left spirals and the number of right spirals are successive Fibonacci numbers.
In geometry, the golden angle is the smaller of the two angles created by sectioning the circumference of a circle according to the golden section; that is, into two arcs such that the ratio of the length of the larger arc to the length of the smaller arc is the same as the ratio of the full circumference to the length of the larger arc.
In mathematics, the Fibonacci numbers are the numbers in the following sequence:
Yeah . . . my eyes just glazed over, too. Interesting yes . . . but . . . OMG my head just exploded.
Anyhoo, typically, there are 34 spirals in one direction and 55 in the other; on a very large sunflower there could be 89 in one direction and 144 in the other.[ The reason for all this math and symmetry and what not is that this pattern produces the most efficient packing of seeds within the flower head.
Sunflowers most commonly grow to heights of between 5 and 12 feet.
Sun flowers have a type of phototropic response called heliotropism (sun turning); the leaves and flower heads of young sunflowers follow the sun and their orientation therefore changes from east to west during the day.
The movements become a circadian response and when plants are rotated 180 degrees, the old response pattern is still followed for a few days, with leaf orientation changing from west to east instead. The leaf and flower bud phototropism occurs while the leaf petioles and stems are still actively growing and once mature the movements stop. The movement occurs as the petioles bend or twist during the day and at night they unbend or untwist.
A circadian rhythm is a roughly 24-hour cycle in the biochemical, physiological, or behavioral processes of living entities, including plants, animals, fungi and cyanobacteria. The term "circadian" comes from the Latin circa, "around", and diem or dies, "day", meaning literally "approximately one day".