Ferns and mosses particularly like to grow in damp places. One of the reasons for this is that, unlike other plants, they have no or less well-developed water pipes and absorb water over their entire surface.

Ferns are very interesting in this respect, as they never form flowers or seeds. Their reproduction is characterized by an alternation of generations, whereby an asexual generation (fern plant with spore capsules) and a sexual generation alternate. In the sexual generation, so-called pre-germs form from the spores if there is sufficient moisture. Their male reproductive organs swim to the female egg cells with the help of a drop of dew or rain, so that a new fern plant can develop.

Special creatures that do not belong to the plant family grow on bare stone, on walls and on the bark of trees. They are hybrids, consisting of a symbiosis* of fungus and algae, and are therefore classified as fungi. Lichens have no roots and absorb moisture and all substances contained in the air unfiltered via their permeable surface. Some species are therefore used as so-called "bio-indicators" to make statements about the air quality of the location.

As very slow and flat-growing organisms, lichens undoubtedly choose these extreme locations because they do not have to fear competition from plants that would immediately cover them up. If lichens settle on walls, masonry or garden furniture, this is not a bad thing, on the contrary: they cover the stone or wood like a protective layer and buffer the effects of the weather well. So please do not remove them!

*Symbiosis refers to the "socialization" of two species, i.e. a coexistence that benefits both sides.

A dry stone wall without mortar is a valuable habitat for many animal and plant species. As a rule, it is very low-maintenance, as the usual fast-growing "weeds" do not stand much of a chance on this barren and nutrient-poor site. The pretty wall plants, such as the wall cinnamon (Cymbalaria muralis), which has been naturalized here since the 16th century, can be easily established by sowing seeds.

Many insects also love the warm stones and cracks. The mason bee even uses existing holes to build its nest.

By the way: If you want to enjoy the rare animal and plant species, leave the pressure washer in the shed - it means the end of biodiversity on the wall.