Rewilding in the garden : are garden hybrid plants (cultivars) less resilient to the effects of hydrological extremes than their parent species? A case study with Primula

Urban green infrastructure, such as gardens, can mitigate some of the consequences of climate change, e.g. reducing flash-flooding or urban heat islands. Green infrastructure, however, may itself be vulnerable to a changing climate, and not all garden and landscape plant taxa will remain viable under weather scenarios predicted for the future. It has been suggested that cultivated forms of garden plants (hybrids and selected varieties) particularly, will be susceptible to enhanced stress associated with more frequent flooding, drought and rapid oscillations between these hydrological extremes; thus potentially limiting the range of taxa that can be used in gardens in the future. This research explored this concept by evaluating cultivated forms of the common garden plant – Primula, and testing whether these were less resilient to the effects of hydrological extremes than their progenitor species, Primula vulgaris. The results support this hypothesis and demonstrated that cultivated taxa were more susceptible to the hydrological stresses imposed than Primula vulgaris. Interestingly though, those cultivars that superficially resembled the parent species (Primula ‘Cottage Cream’) showed more stress tolerance than others with larger or more ornamental flowers, suggesting a ‘gradient of susceptibility’ within the hybrids. The notion that the most flamboyant cultivars are sacrificing stress tolerance for traits linked with aesthetics is discussed. The data, albeit on one genus only, has implications for the design of gardens/ornamental landscapes for the future and calls for more attention within breeding programmes to enhance abiotic stress tolerance within garden and landscape plants.