Code for a Fractal Fern

import graph;

size(0,220);

//scale factor
real r=0.3;

//initial picture (stalk)
path P=(0,0)--(0,1);

//iteration
picture step(picture p)
{	
	picture a=shift((0,0.75))*scale(r)*p;
	add(a,shift((0,0.7))*rotate(70)*scale(r)*p);
	add(a,shift((0,0.6))*rotate(-70)*scale(r)*p);
	add(a,shift((0,0.5))*rotate(70)*scale(r)*p);
	add(a,shift((0,0.4))*rotate(-70)*scale(r)*p);
	add(a,shift((0,0.3))*rotate(70)*scale(r)*p);
	add(a,shift((0,0.2))*rotate(-70)*scale(r)*p);
	return a;
}

//Print fractal dimension
write(-log(7)/log(r));

//number of iterations (less than 5 if you want it to compile!)
int n=5;

picture calc;
draw(calc,P,linewidth(0.2));

picture[] pp={calc};

for(int i=1; i<=n; ++i){
	pp[i]=step(pp[i-1]);
	//Uncomment to see the stalks
	//draw(pp[i],P,linewidth(0.1));
}

add(pp[n]);