The vegetation of the Rhön is very diverse. This is primarily caused by divers climate and soil conditions in a relatively small area.
On steep rocky and basalt boulder slopes forest could never spread because of unfavourable environmental conditions. Thus, plant species have been preserved which, in other landscapes, were replaced by forests at the end of the ice age. Additionally, human soil use contributed to the diverse vegetation of the Rhön because some plant communities need extensive grazing. A rich inventory of Trollius europaeus, orchids, Arnica montana or Carlina acaulis should be mentioned here.
In the Rhön, forests cover only one third of the total area although they are dominant in many other German low mountain ranges. Although the share of coniferous trees especially of spruce is steadily increasing, beautiful mixed deciduous forests (beech forests and mixed beech forests) enriched by other tree species according to soil type and elevation are preserved. The rich and well-developed herbaceous layer of these forests varies according to nutrient supply, especially soil reaction and soil moisture. This is why different vegetation units could develop which are especially rich on limestone. The high number of orchid species, which are all under legal protection, is eye-catching.
On steep rocky slopes, gorges and stony shady slopes forests can be found in which the beech tree - dominant in many other habitats- plays no or only a secondary role. Mostly, Acer pseudoplatanus, Fraxinus excelsior, Ulmus glabra or Acer platanoides can be found. Especially typical for this forest community is the nature reserve "Kesselrain", the "Eisgraben" and partly the nature reserve "Schafstein". Again more diverse is the forest community at the "Milseburg".
In always or partly watered areas such as valleys and sinks usually floodplain and source forests represent the final stage of vegetation development. However, they are almost not existing any more in the Rhön because these areas were soon used as meadows. In contrast, numerous belts of trees and shrubs along creeks out of Alnus glutinosa, Fraxinus excelsior and Salix spp. give a characteristic feature to the landscape.
In general, unregulated near-natural rivers and creeks with their good water quality are very valuable for nature conservation and tourism. Shrubs often developed on forest edges, clearance cairns and drift paths. In former times, hedges were planted to delimit pastures and for wind protection. Juniper meadows are decreasing because more and more pastures are replaced by intensively used meadows and forests. In the Hesse part of the Rhön, impressive examples can still be found, for instance the protected drift path of the former pasture "Eselsbrunner Hute", the nature reserve "Oberbernhardser Höhe", some pastures below the "Pferdskopf" and on the slopes of the "Biebertal" in Kleinsassen. Important large-scale Juniper meadows can be found especially in the Thuringian Rhön, for instance in the nature reserve "Wiesenthaler Schweiz". Also the Felda valley has numerous Juniper drift paths, for instance the "Fischbach".
Even more impressive is the unique vegetation of the two raised bogs "Rotes Moor" and "Schwarzes Moor". The growth of mires and the accumulation of new peat is especially caused by some peat moss species. In-between, cotton sedges (Eriophorum latifolium), sundew (Drosera rotundifolia), cranberry (Oxycoccus spec.), other healthy species and Empetrum spp. occur. On dry spots, groups of shrubs can develop in which birch, Salix caprea, and various coniferous trees often dominate with single individuals. One of the rarities in the Rhön mires is Betula carpatica.
In particular, numerous sources and creeks of the Rhön have herbaceous rich plant communities. Especially during flowering time, the yellowish white of the Meadow sweet (Filipendula ulmaria) plant communities on creek banks and the red to violett flowers of Ranunculus palustre, Lythrum salicaria and Epilobium hirsutum attract the attention of visitors. Big-leafed Petasites communities can be found especially along big creeks with cold mountain water.
As already mentioned, steep cliffs out of phonolith or basalt cannot be covered by forest in these exposed areas. In crevices, Asplenium communities can be found. Other fern communities grow in shady humid areas. According to the fine earth content one can find Festuca pallens communities with Dianthus gratianopolitanus and Sedum species and, under favourable conditions, also different shrubs such as Mespilus germanica and Sorbus aria underneath of which many colourful herbs are growing. On boulder, rocks and clearance cairns, many mosses and lichens which usually grow only under arctic, sub-arctic and alpine conditions are developed in a remarkable density.
From spring to early summer, mountainous meadows develop their divers species flora and remind visitors of the same views in Alps valleys which are also characteristic for the Rhön. According to land use, elevation and climate conditions, the vegetation of these meadows, pastures and rough grazing land changes. Therefore, during flowering time, the landscape has a very diverse appearance. In order to maintain the characteristics of the Rhön landscape various protection measures are taken by the responsible administrations.
Reference: Die Rhön, Landschaft und Geschichte - Eine Kurzinformation, Gerhilde Kramm, Schriftenreihe des Rhönklubs e.V.