Excessive heat is very stressful for most rhododendrons and azaleas with the possible exception of some the Japanese azaleas which have been bred to withstand heat. There are also some large leaf rhododendrons beginning to appear which have rhododendron hyperythrum as a parent which have also been bred to be growable in very warm climates. In any case, even these would not be able to take much direct sun exposure. A dry summer climate would only add to the difficulty as a relatively high degree of atmospheric moisture is necessary for rhododendrons to grow well. The area around Lake Como would be both cooler because of altitude and have moister air.

It would be easy enough to check soil pH with a basic kit sold for that purpose. The physical structure of the soil, however, is just as important as pH. Rhododendrons and azaleas need a planting medium that consists of at least 25% - 50% is better - organic matter. Then there is the fact many root diseases become much more of a problem when the planting medium reaches a high temperature.

Camellias are better adapted to hot climates than the vast majority of azaleas and rhododendrons even though they also require acid soil. Pot culture may be successful because of the extra attention the plants receive. Large terra cotta type pots also provide natural cooling through evaporation.

Thanks for your reply, akamainegrower. Altitude-wise,I am at about 650 meters above sea level; possibly higher than Lake Como, but definitely with much drier air. It's a fascinating subject...bart

Another possibility which occured to me after my first post: there are several rhododendron species - the maddenii group comes to mind - which are grown successfully outdoors in places like California and Australia. Checking into specific information from these climate areas may give you some further ideas of types to experiment with in your location. Many are, I'm quite sure, available by mail order to EU countries from nurseries in England, Germany and probably other places. A simple misting system would not be terribly hard to install and would do much to address the problem of atmospheric dryness. You might become the founding father of Tuscan rhododendron culture.