Two summers ago an acorn sprouted in one of my window boxes. I promptly re-potted it an gave it some TLC. It thrived. The following summer another little acorn popped up in the same pot! I then re-potted the pair into an even bigger pot, and they continued to do well. But, they needed to be properly planted in the ground. It's illegal to go planting wherever you like in public parks, so we went under the cover of darkness! These little guys are now hopefully spreading their roots in a sensible part of Westerpark. I hope they do well, and I'll keep my eye on them for as long as I'm living in Holland. I hope one day they're big old oaks!