Yes, and the river dales of rhine, main, donau etc... enforce this effect too. Warm air from the south can come far north beside the alpes...

Here some more pics from southern german inner city trachys or Exotic plants:

http://i260.photobucket.com/albums/ii33/flecky8/Bild052.jpg?t=1218053313
http://i233.photobucket.com/albums/ee139/JoJaeck/Chris%20Stuehrk%202008-2/Bild069.jpg
http://i233.photobucket.com/albums/ee139/JoJaeck/Chris%20Stuehrk%202008-2/Bild214.jpg
http://i233.photobucket.com/albums/ee139/JoJaeck/Chris%20Stuehrk%202008-3/Bild004.jpg
http://i233.photobucket.com/albums/ee139/JoJaeck/Chris%20Stuehrk%202008-3/Bild083.jpg
http://i233.photobucket.com/albums/ee139/JoJaeck/Chris%20Stuehrk%202008-3/Bild121.jpg