Sunflower, Sunflowers,
What is usually called the "flower"
on a mature sunflower is actually a "flower head" (also known as a
"composite flower") of numerous florets, (small flowers) crowded
together. The outer petal-bearing florets are the sterile florets and can be
yellow, red, orange, or other colors. The florets inside the circular head are
called disc florets, which mature into seeds.
The flower petals within the sunflower's cluster are usually in a a spiral pattern. Generally, 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. 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. This pattern produces
the most efficient packing of seeds within the flower head.
Sunflowers most commonly grow to heights between 1.5 and
3.5 m (5–12 ft). Scientific literature reports that a 12 m
(40 ft), traditional, single-head, sunflower plant was grown in Padua in 1567. The same seed lot grew almost
8 m (26 ft) at other times and places, including Madrid. During the
20th century, heights of over 8 m have been achieved in both the Netherlands and Ontario, Canada
