Forest plant communities are extremely diverse – and their horticultural management is correspondingly demanding. The occurrence of forest perennials is determined by several factors acting simultaneously: region, climate and soil conditions, but above all by the trees themselves.
Root competition: Trees have a decisive influence on the available habitat in and on the soil. Spruce (Picea abies) spreads its roots shallowly beneath the soil surface, whilst the silver fir (Abies alba) roots deep into the ground – which improves water availability.
Soil quality: Through the fall of leaves and needles, trees also influence the chemical composition of the soil. Leaves and needles decompose at different rates and release various substances – not all of which promote growth. The leaves of the walnut tree (Juglans regia) can be toxic to other plants. This phenomenon is called allelopathy.
Light: For many forest perennials, access to light is vital. They have developed a clever strategy: they flower early in the year, before the canopy of trees closes. Later, they produce large, shading leaves to capture as much light as possible even in the semi-darkness.
Leaves and needles differ fundamentally in their rate of decomposition, their constituent materials and the soil conditions they create. Leaf litter decomposes much more rapidly and forms nutrient-rich, crumbly humus. Needle litter, on the other hand, decomposes slowly, acidifies the soil and leads to the formation of raw humus.
Balkan cranesbill − Geranium macrorrhizum
Hazel-leaved butterwort − Pachyphragma macrophylla
Carinthian cow-foot − Wulfenia carinthiaca
Haberlea − Haberlea rhodopensis
Spring snowflake − Omphalodes verna
Pyrenean rock cress − Ramonda myconi
