Putting conservation gardening into practice

Abstract

Conservation gardening (CG) represents a socio-ecological approach to address the decline of native plant species and transform the gardening industry into an innovative conservation tool. However, essential information regarding amenable plants, their ecological requirements for gardening, and commercial availability remains limited and not readily available. In this study, we present a workflow using Germany as a case study to bridge this knowledge gap. We synthesized the Red Lists of all 16 federal states in Germany, and text-mined a comprehensive platform for garden plants, as well as multiple German producers of native plants. To provide accessible information, we developed a user-friendly app ( https://conservation-gardening.shinyapps.io/app-en/ ) that offers region-specific lists of CG plants, along with practical guidance for planting and purchasing. Our findings reveal that a median of 845 plant species are red-listed across federal states (ranging from 515 to 1123), with 41% of these species amenable to gardening (ranging from 29 to 53%), resulting in a total of 988 CG species. Notably, 66% of these species (650) are already available for purchase. Additionally, we observed that many CG plants exhibit drought tolerance and require less fertilizer on average, with implications for long-term urban planning and climate adaptation. Collaborating with gardening experts, we present a selection of purchasable CG balcony plants for each federal state, highlighting the feasibility of CG even for individuals without gardens. With a multitude of declining plants amenable to gardening and the vital role of gardens as refuges and green corridors, CG holds substantial potential to catalyze transformative change in bending the curve of biodiversity loss.

Figure 1

Between 29 and 53% of endangered species in German federal states are amenable to gardening, including extinct and critically endangered species. (a) Number of red-listed species listed per federal state (blue), and number of red-listed species also listed in NaturaDB aka Conservation Gardening (CG) species (orange). (b) Percentage of red-listed species that are amenable to CG. (c) Distribution of CG species across Red List categories (0 = Extinct or lost, 1 = Critically endangered, 2 = Endangered, 3 = Vulnerable, G = Endangered—unknown extent, R = Rare, V = Near threatened).

Figure 2

The majority (66%) of CG species is already produced and available for purchase. (a) Cumulatively across German federal states, we count a total of 988 distinct CG species. Of these, 650 species are already listed in the assortment of major native seed/plant producers in Germany. (b) Distribution of the number of produced CG species across producers. (c) Distribution of produced CG species in absolute numbers across Red List categories.

Figure 3

The average CG species is more likely to tolerate drought, and requires less fertilizer input. (a) Comparison amongst conventional gardening species (n = 134) and CG species (n = 475) in their water requirements (dry, moist, wet). (b) Comparison amongst conventional gardening species (n = 307) and CG species (n = 870) in their nutrient requirements (N poor, intermediate, N rich).

Figure 4

CG holds substantial potential to catalyze transformative change in bending the curve of biodiversity loss. (a) Current threat status versus potential threat status if CG were widely implemented (see Methods). (b) The transformative potential of CG at the level of Germany as a whole, using the 2018 Red List for the nation. Circular bar plots indicate the number of species in the Red List categories 0-V (left), and the number of red-listed species in these categories if CG would come to its full potential (right), i.e., subtracting CG species from the number of red-listed species. Maps were created in R, version 4.3.1 (https://r-project.org/).

Figure 5

CG species for balconies for each federal state. Five exemplary CG species that can be grown on a balcony. Shown is the name of the species, the Red List category (in parentheses), and the purchase price (for clarity of availability, but note that prices are dynamic and apply here as of January 2023). For more planting possibilities for the balcony (also checked by practitioners) see Supplementary Table 2. Map was created in R, version 4.3.1 (https://r-project.org/).