Preferred numbers and golden ratios in the botanic garden
Have you ever wondered why four leaf clovers are so rare? It may be because four is not a Fibonacci
number.
The Fibonacci sequence is named after Leonardo Pisano Bigollo known as Fibonacci, a twelfth
century mathematician born in Pisa. Fibonacci is best known for spreading the Hindu‐Arabic number
system (ten digits and a decimal point) in Europe superseding the Roman numeral system.
The Fibonacci sequence begins with 0 and 1. The next number is found by adding the previous two
numbers, and then this pattern is repeated.
0,1,1,2,3,5,8,13,21,34…and so on. Fibonacci numbers regularly occur in nature.
The flowers in the daisy family (Asteraceae) one of the largest if not the largest of all plant families,
often have 21, 34, 55 or 89 petals. These numbers are the 8th, 9th, 10th, and 11th numbers in the
Fibonacci sequence. Try counting the petals of the lilac coloured Brachysome Daisy (Brachyscome
multifida) near the turtles in the Sensory Garden.
Fibonacci numbers can also be seen in the arrangement of seeds on flower heads. If you study a
sunflower you will notice that the seeds are packed in clockwise and anti‐clockwise spirals. The
numbers of spirals in each direction are (almost always) two numbers which are next to each other
in the Fibonacci sequence. Look for spirals obeying the same rule on pine cones and pineapples.
The regular occurrence of Fibonacci numbers is not restricted to plants. Take a look at your body:
one body, two arms, three segments to each arm and five digits!
Preferred numbers, golden ratios and golden sections (arcs) occur throughout nature, art,
architecture, poetry and music.
In some plants the correlation may just be a coincidence. In other situations, preferred numbers and
ratios may exist because particular growth patterns are more effective at enabling maximum
exposure for light‐hungry leaves and optimal seed arrangement.
By Ian McAlister & Karen Hagan