I like it!
To get rid of the crash, you should count the entities and stop growing at a certain limit.

Do you know the nvidia tree demo? Its probably from2001, couldn't find a download in the web, though.

Main difference: it didn't grow like yours, but it gave you parameters to adjust the size and spin and density of leaves etc. And, you could choose day mode and night mode, while in night mode you could watch fireflies flying through the crown of the tree illuminating its branches and leaves in different colours!
Very nice! Maybe, you like to combine your idea with that!?