The Geographic Beds consist of six collections, each representing a different biogeographic region:
- The Mediterranean Basin
- South Africa
- South America
- New Zealand
- Japan
The beds highlight the diversity of these regions, and the evolutionary adaptations of the plants in response to environmental pressures. For example, many of the plants found in the Mediterranean basin have highly scented, densely haired leaves containing essential oils. These features are an adaptation to drought stress, preventing excess loss of water from the plants during photosynthesis. A characteristic trait of plants from New Zealand is a growth form known as 'divarication', in which branches grow in a zig-zag fashion with much reduced leaves. This is thought to be an adaptation to prevent grazing of such plants by moa, a now-extinct native bird.
The Garden plans to develop these collections further, focusing on regions of the world known as 'biodiversity hotspots'. Such areas hold high numbers of endemic plant species, yet face substantial threat to their natural vegetation. Over 50% of the world's plant species are contained within these hotspots, which together cover only 2.3% of the Earth's land surface.
The Geographic Beds are situated within the Walled Garden, adjacent to the original 17th century walls, which provide a sheltered microclimate that allow the cultivation of a number of borderline-hardy species.
