Hello,

i´, from southern Germany, an a palm fan.
I connot follow exactly your discussion but i can say:

Rhine/Main Area (Cologne-Frankfurt, Mannheim- Karlsruhe (= wine area)) and Freiburg, Würzburg-Nürnberg Area (wine area) and Bodensee, had a special climate, very mild in winter (max. -10°C, in the city centre often only -5°C, don´t believe the weather station, because they are often outside of the city at the airport or in the forrest) and hot in summer(average highest about 25-30°C). So the vegetation time is from end of march to end of October in the cityareas. So to say there is a micro climate.
Ficus Carica, Euc. Gunnii, Olea europea, Trachys, Photinia, Lagerstoemia indica and Cupressus Sempervirens are often seen in privat gardens an city places and squares.
Th palmengarten frankfurt or the insel Mainau in the bodensee are the most known mediterrean gardens in southern Germany.
Most foreigners can´t belive this, but this few areas i mentioned above are very well known for wine and meditterinean climate north of the alpes.

But away from the rivers and big citys, the climate is like in Denmark or sweden because of the mountains (500-1500mm over NN).

In my neighbourhood in nearly each garden you can find a Cupressus semp, Trachy, or a ficus carica.

Do you can post pics of scandinavian exots?

MvH

Markus