I think warmer is better. I’m zone 8. Do they have that zone system in Germany? I think that’s where you are, right? But anyway it needs 110 warm days to grow so you have to time it right I think. I planted it in 3 successions.
Yes there is a zone system also for Germany (and yes you guessed right) - I am sadly in zone 6, so it probably will be pretty hard for me to grow these..