tree church
An outdoor church whose walls and main structure are formed almost entirely from trained living plants, usually trees.
Pictured: Weidenkirche
A tree church is an outdoor church whose walls and main structure are constructed almost exclusively from trained plants, usually trees growing over a thin framework. These are especially common in Germany, where a number of "willow churches" (Weidenkirchen) have been built.
The trained plants supply the walls and principal form. A thin framework can guide their growth without replacing the plants as the dominant structure.
An ordinary church merely surrounded by trees has a different construction. In a tree church, the living plants form the worship space itself.