Sunflower rule

Each new seed goes where there is most room. The spirals follow.

A sunflower head filling seed by seed until it holds 1,500. The newest seeds stand out most, at the center, and the spirals at the edge climb from 8 and 13 to 55 and 89.

The head is a model. Our recount of 400 measured heads matches the paper: of their 768 spiral counts, 565 are Fibonacci and 67 sit in related series. Started gently, the rule lands on Fibonacci every time. A third of real heads do not, and noise is one way there. With one seed in fifty out of order, six modeled heads in ten leave Fibonacci.

Rule after Douady & Couder 1992. Heads: Swinton et al. 2016, Turing's Sunflowers (CC0).

Read the paper: Swinton et al. 2016