Ok, I admit I'm a little late... but this such a lovely initiative that I have to share it: Tuinboon Je Mee? It's a very simple initiative to make Amsterdam a greener city by encouraging people to plant broadbeans all over Amsterdam.
Apparently the result of your good green deed will be beautiful white flowers with little black hearts. And on top of that you can harvest the very tasty, young broadbeans to throw on your dinner plate! In February and March people planted horsebeans all over Amsterdam, here's a map of the specific locations - so keep your eyes peeled. Thanks for making our city greener! :-)