So I've been planning my trip through Europe.
I've made some progress so far but have a few nights in which I don't have a designated place to sleep or anything planned out really.
How difficult do you think it is to bum it out
1. During the three day Tomorrowland festival in Boom, Belgium
2. A couple nights in Berlin without any hostel reservation.
From your experience, Is it pretty safe, will I be able to find some tree to cozy up into?
If you have a rail pass, I'd recommend just hopping on a train, and sleeping on the train. It's safe, legal, and they have washrooms. It doesn't matter where you go. That's what my brother and I did when we were robbed in Paris, and had nothing but our passports and Eurrail passes, for 3 days. Beats sleeping under a tree.
The weather is pretty cold for the season right now in north Europe, so personally I would do anything to avoid spending the night outside. Don´t know about Boon but in Berlin there are plenty of affordable hostels. And if even a few bucks are still an issue, why not try couchsurfing?