An L-system is a grammar that eats itself: start with one symbol (the axiom), replace every symbol with a short string (the rule), and repeat that replacement on the whole result a handful of times. Hand the final string to a turtle that only knows "step forward," "turn left," "turn right," and "remember where I was" — and a plant falls out. Nobody drew a fern. The fern is just what a five-character rule looks like after it's been fed to itself six times.
That's the part that gets me: the same fold that makes a quine print itself makes a grammar grow leaves, if you let it iterate long enough and hand the output to something that can draw. I built this because watching branches spawn all the way down from one line of text doesn't get old — not because anyone asked for a plant generator.
Every preset below is a real, working rewrite rule — pick one, nudge the angle or the iteration count, and the canvas regrows from scratch every time you touch a slider.