When creating green spaces, the city of Offenbach am Main, like other municipalities, uses mulch layers to protect the plants and the soil. These can consist of bark mulch or, in the case of suitable plants, gravel.
Head of Building and Planning Paul-Gerhard WeißIn appearance from above, the difference between gravel mulch and so-called gravel gardens is small - but in reality it is very big. While gravel gardens are rightly criticized, mineral mulch areas are a prime example of sustainable design.
Mineral gravel is one of the most sustainable planting concepts. In contrast to the gravel garden, no separating layer is placed under the gravel. Soil organisms and microorganisms are not suppressed and water can penetrate and seep away. Mineral gravel (or lava rock) is used in areas where high levels of drought are to be expected. Plants that tolerate this well are used here and the light-colored gravel reduces the temperature and evaporation of the water present in the soil. The combination of mixed perennial plantings and mineral mulch creates valuable habitats for bees, butterflies and other species. It reduces the amount of maintenance required by the city because weeds are suppressed. Visually, the mulch layer disappears after a short time, as the planting becomes so dense that the soil is barely visible, at least during the growing season.
An example of the successful use of this technique can be found at Herrnstrasse 38: while the shady areas were covered with organic mulch, a mineral layer protects the plants from drying out in the sunny areas.
"The confusion between gravel gardens and mineral mulch areas often leads to criticism of what are actually sustainable planting concepts. But they couldn't be more different: gravel gardens are sterile, heat-inducing problem areas. A mineral mulched bed is a solution to the challenges of modern cities: it combines natural design with ecological benefits and makes a valuable contribution to biodiversity and sustainability," adds Christoph Russ, Head of the Open Space Planning and Urban Greenery Department at the Office for Planning and Building.
