JoeR
Masterpiece
I would say the key to keeping them in borderline climates would be to keep the pot and roots as cool as possible. Tinfoil, shade cloth, something to keep the sun off the potI think Germany has colder and longer winters than NJ
New Jersey is right next to my state and just south of me. My climate is very very similar but NJ is slightly hotter.
Larch do fine in Northern NY but they can be tricky here in southern NY. They dont grow naturally here.
I have what I think is a Japanese Larch which can tolerate warmer weather than North American Larch.
Ive managed to keep alive. A friend of mine has had trouble with them.