Draft:Three-Zone-Gardening



The concept of the three-zone garden, also known as Hortus, is a combination of permaculture and wildlife garden elements. It is not to be confused with the USDA Plant Hardiness Zone 3.

The aim of Three-Zone-Gardening is to create a garden that contributes to strengthening local biodiversity and allows food to be grown sustainably without the addition of external resources such as fertilizer. The model is adapted to a temperate climate and always consists of the following three zones: buffer zone, hotspot zone and yield zone. The species-rich hotspot zone, with its poor soils, supplies the nutrients for the yield zone in which fruit and vegetables are grown. The concept was developed by german nurse and garden book author Markus Gastl. In the 'Hortus Network', which he also initiated, over seven hundred gardens that work according to the three-zone model are networked. The Hortus Network is an official project of the United Nations Decade on Biodiversity.

Nutrient flow in the three-zone garden
By deliberately keeping the hotspot zone nutrient-poor, nitrogen-rich green waste is constantly produced in a three-zone garden, which is used as fertilizer for the yield zone. This ensures the biological diversity of the hotspot zone, as stronger plants cannot settle there and displace the native flowering plants. The garden's own fertilizer replaces external fertilizers and substrates used in many other gardens. In order to ensure a sufficient nutrient supply to the yield zone, both areas must be in a suitable size ratio to one another and the runoff of nutrients from the yield zone must be prevented. A dry separation toilet, for example, closes the nutrient gap that would otherwise arise from consuming the gardens food.

Hotspot zone


The hotspot zone replicates increasingly rare, nutrient-poor habitats from the natural and cultivated landscape. IIt is characterized by a greatly reduced humus content and offers a habitat for many threatened native flowering plants, for which it becomes increasingly difficult to prevail against high-growth nitrogen indicator plants in a cultivated landscape that is often over-fertilized. Integrated 'nature modules' (see below) offer ecological niches for numerous insects and wild animals. The areas of the hotspot zone can be gradually emaciated by removing the clippings after mowing. Alternatively, a poor soil condition can be artificially achieved when the garden is being laid out by removing the humus layer or applying mineral substrate (gravel, sand or broken brick). Mowing the poor areas only takes place once or twice a year, but is essential for maintaining the poor soils, as the clippings are removed from the hotspot zone and therefore do not contribute to fertilizing the areas. This corresponds to historical models from agriculture before the introduction of mineral fertilizers. The long intervals between mowing operations help insects to use the plants more successfully as a nesting place for reproduction.

Yield zone
The yield zone corresponds to an ecologically managed kitchen garden, planted in mixed culture. To increase soil fertility, this zone is fertilized with green waste and organic material from the other two zones. This happens, among other things, through surface fertilization with mulch.

Buffer zone
The buffer zone shields the garden from the outside. It consists of hedge structures of native wild plants and primarily serves as a refuge and food source for wild animals. The cuttings from this zone are also predominantly brought to the yield zone.

Nature modules and super beds


Nature modules are individual design elements in the three-zone garden that have a particular benefit for wild animals. These are predominantly built in the buffer and hotspot zones and ensure a high level of structural diversity. Examples of this are dry stone walls as heat storage for heat-loving species, deadwood hedges, watering holes, permanently moist habitats for beetles (beetle cellars) or nesting aids for ground-nesting insects (sandarium). The natural modules create numerous microclimate zones within a zone, from full sun to shady, and ecological niches. The modules provide shelter, night and winter quarters and are used as breeding grounds or hunting grounds.

Gastl describes raised beds as superbeds because, depending on the substrate and plants used, they can be used as a lean location (hotspot zone) or vegetable patch (yield zone). They can be used to create all zones even in small gardens and in larger gardens they increase the structural diversity and thus usually also the species diversityt, because the three zones are less clearly demarcated.

Hortus Network
The Hortus Network is a network of gardeners who are developing their garden into a three-zone garden. The Hortus network and the participating gardens are part of the UN Decade of Biological Diversity. According to information on the network's own website, there are currently over 750 participating gardens in Germany, Austria, France, Croatia, Hungary, Switzerland and the USA.

Markus Gastl
The concept of the three-zone garden was developed by Markus Gastl after a two and a half year bicycle trip from Tierra del Fuego to Alaska in order to do something for the local nature out of gratitude for the experience[7]. His idea was to combine the classic wildlife garden, which primarily serves to promote biodiversity, with elements of permaculture, which historically primarily teaches the sustainable cultivation of crops in mixed culture. The first project was Gastl's own 7,500 m² garden in Beyerberg, Bavaria. The garden is now called 'Hortus Insectorum' and is accessible as a show garden. In 2018, Gastl was awarded the Bavarian State Medal for special services to the environment.

Literature
Markus Gastl: Three-Zone Garden: Diversity · Beauty · Benefits, 2015, Pfeil Verlag, Germany, ISBN 978-3-89937-154-3. Markus Gastl: Permaculture and natural gardens, 2021, Ulmer Verlag, Germany, ISBN 978-3-8186-1376-1. Markus Gastl: More nature in the garden: Simple projects with a big impact for vibrant diversity, 2021, Ulmer Verlag, Germany, ISBN 978-3-8186-1346-4.

Web links

 * German-language website of the Hortus Network
 * Website of the first three-zone garden by Markus Gastl