Ingmar R. Staude

1. Gardens hold untapped potential for participatory biodiversity conservation. Conservation gardening has recently emerged as a way to foster declining native plant species in urban and rural green spaces. But the impact of cultivating these species on population trends in the broader landscape remains underexplored.
2. Here, I study the effects of cultivating herbaceous native plants on species' long-term population trends and endangerment. I integrate the comprehensive cultivated flora of Rothmaler's "Herbaceous Ornamental and Crop Plants" in Germany, and the German Red List of 1998 and 2018. I ask whether cultivating native plants, particularly frequently cultivated ones, reduces their risk of endangerment; whether cultivated species, based on their cultivation frequency, tend to display more optimistic long-term population trends; and whether cultivation may even contribute to improving Red List statuses.
3. I find that cultivated species, especially those commonly grown in gardens, were less likely to be endangered. Moreover, commonly cultivated species had fewer declining and more positive long-term population trends compared to non-cultivated species. Some evidence suggests that commonly cultivated plants in 1998's Red List category are more likely to improve their status, yet still a considerable proportion is in decline.
4. These findings hint at a promising role of gardens as a means to support native species populations, but they also underscore the need for a nuanced understanding of which species are most likely to benefit from cultivation.