Garden Habitat-based Classification of Perennials: Richard Hansen’s Framework†

Richard Hansen (1912–2001), a German botanist, horticulturist, and landscape gardener, developed his own unique theory by defining the garden as a habitat for perennials and classifying types of garden habitats. This study analyzed the perennial classification system specially established in ⌜Perennials and Their Garden Habitats (1981)ᒧ, Hansen’s comprehensive work, in order to understand the adaptive environments of perennials he discovered through experimentation and the conditions necessary for their introduction into gardens. Hansen categorized garden habitats into woodland, woodland’s edge, open ground, rock gardens, borders, water’s edge, and water, thereby encompassing a wide range of landscapes adaptable to gardens. From the analysis of the seven habitat-based perennial classification features, several points can be highlighted. First, Hansen did not apply uniform criteria to subdivisions of each habitat but instead established diverse and detailed conditions tailored to the characteristics of each habitat. Second, the names of the classification categories, which reflect Hansen’s keen achievements in plant observation, revealed three attributes as the basis for classification: growing environment, plant characteristics, and application methods. Third, Hansen included plants from diverse regions as well as cultivated varieties. Among these, plants such as <italic>Vinca minor, Ajuga reptans, Omphalodes verna, and Gentiana asclepiadea</italic>, which appeared repeatedly across multiple habitats, were identified as highly versatile species. Plants designated in the classification as characteristic of particular habitats included ferns, <italic>Hosta</italic>, and grasses in the woodland habitat; daffodils in the woodland’s edge; tulips, lilies, hyacinths, <italic>Kniphofia</italic> and grasses in the borders; gentians in the rock gardens; grasses, <italic>Erica</italic> and <italic>Calluna</italic> in the open ground; and water lilies in aquatic habitats. These can be regarded as the key plants of each respective habitat. Fourth, Hansen proposed plants suited to the special conditions of woodland, woodland’s edge, rock gardens, water’s edge, and water habitats except for borders, while in the woodland, rock garden, and border habitats he introduced plants specifically appealing to plant enthusiasts, thereby reflecting the interests of gardeners and expanding the diversity of plant selection.