Just caught the post by flagamuffin:

(tagging flagamuffin twice in one day!)

Had to post this webapp that lets you play with different angles for seed placements. You can control angle, seed size, number of seeds, and which multiples of seed numbers to connect to see the spirals more clearly. Arrow keys let you finely control angle and spirals. And there's some buttons to give you phi, π, e and √2 with one click.

Here's a paper about how the golden ratio pops up in the plant world.