John Walker wrote a great article called “Fractal Food, Self-Similarity on the supermarket shelf” about fractals in nature in general and specifically one of the most recognizable fractal shapes in nature, namely the shape of the “Romanesco (broccoli)“. The article explains the basics on how the shape can be replicated with a mathematical system called “Cellular Automata” and it also has some great photos.
Sang-Hoon Kim wrote a related scientific paper called “Fractal dimensions of a green broccoli and a white cauliflower” on the subject in 2004 at the Mokpo National Maritime University (MNMU) in Korea.
Aleksandar Rodic made a great 3D animation using a technique called procedural modeling to build the similar mathematical shapes of the Romanesco. He even wrote an article on how the 3D broccoli animation was made.