Hi,
firstly, I live in Germany and I came across your post this morning while looking for places to camp. While the below doesn't directly answer your question, it might offer some tips about what to consider when wild camping (or planning to) in Germany.
I have a pocket German dictionary with travel tips, which states that "Wild camping in great Britain is not allowed!" (I already contacted them to let them know about Scotland). From this I assumed that in Germany it is allowed, but apparently it's not that simple. There is some info
here in German, to paraphrase, it's not permitted in Germany, it is in Sweden, Scotland, Norway, Finland and Switzerland, where there is a kind of "right to roam" type law. The laws which govern land access here seem to be made at state level, so it's different in different parts of the country.
http://www.outdoor-magazin.com/service/tipps-on-tour/wild-zelten-aber-richtig.264458.3.htm
http://www.outdoor-magazin.com/service/touren-und-planung/wild-zelten.84199.3.htm?skip=
It looks like in the south of the country there are state laws that allow anyone on open land, except in agricultural use (which includes forestry!). Germany is densely populated, and the population here seems not to be as concentrated in a few metropolitan areas as it is in England. I've yet to find anywhere that feels remote in the sense that much of the British upland spaces do. There are also a lot of forests (which are actively managed, and thus seem to have some restrictions as to use), a lot of game (deer/wild boar) and a lot of hunters. The above factors make it a fairly dangerous and probably illegal affair to pitch a tent in a forest, and one of the tips in the above links is to hang a flashing light on your tent so you don't get accidentally shot. Apparently creating any kind of fire (including with a gas stove) withing 100M of a forest seems to be prohibited under German law. This doesn't apply to "open landscape" but so far on my travels I haven't seen much of Germany that isn't covered in either forest or agricultural land.
An interesting reflection on German land use by a early C20th American forester, which certainly chimes with my experience.
http://findarticles.com/p/articles/mi_m1016/is_n5-6_v97/ai_10737438/
Anyway sorry I haven't really contributed anything! I reckon the best places to wild camp are likely to be places without managed forest.