Rhododendrons – origins and extension
Rhododendrons are the remainder of plentiful Tertiary period flora. In this geological period, unusually favourable climatically, the spread of Rhododendrons was much wider than it is today, and it is suggested that it was virtually uninterrupted. Ice ages in Quarternary period, though, saw living through of only the kinds with favourable conditions in their locality or with the ability to well adapt to harsher climates .
Generally, rhododendrons are either a part of forest communities or grow close above the forest level, where they create smaller but also some larger continuous vegetation. They grow in more sour, mainly humic soil. Only a few species grow on calcites, since the vast majority of them cannot bear an alkalic soil reaction.
Rhododendrons are plants not well-suited for sudden temperature changes during the day, and so the species growing outside the forest microclimate (thus outside forest borders) inhabits northern or western lopes more, but always on the leeward side of the hill. The individual areas of presence, though, have their specific conditions. Hence, by the origin, we distinguish Rhododendrons from three main regions:
- rododendrony asijského původu
- rododendrony australského původu
- rododendrony evropského původu
- rododendrony amerického původu
• Rhododendrons of Asian origin;
• Rhododendrons of Australian origin;
• Rhododendrons of European origin;
• Rhododendrons of American origin;