Japan & Russia 2018
Botaniska's scientific curator Henrik Sjöman undertook a far-reaching study expedition in Japan and eastern Russia during the summer of 2018, partly to study magnolias in their natural habitats. Increased understanding of how they grow in the wild will provide us with invaluable knowledge and guidance about how we should care for them in our gardens in Sweden.
The expedition was carried out in collaboration with Sheffield University (England), Vladivostok Botanical Garden (Russia) and Kyushu University (Japan).
The natural variation of plants
Species that are widely spread geographically have locally developed unique characteristics to cope with their unique climate and to compete for the natural resources around them and develop successfully in their unique growing conditions. We know very little at present about how great the differences are between various populations of the same species, depending on the climate and growing conditions from which they originate. Nowadays, when we are more often experiencing a changed climate with warmer and sometimes drier summers, this knowledge is especially important since we must learn which genetic material is most suitable for a more challenging climate.
In Japan, there are many species that are widely spread out along a south-northerly axis. In this population, one and the same species may experience many different types of climate, with warmer and drier conditions in the south and cooler and wetter conditions in the north. During the five-week-long field trip in 2018, the main aim was precisely to study these species growing in different types of climate, in order to identify which origins are most suitable for our gardens in Sweden and western Europe.
Magnolias and ecological strategies
In botanical literature, magnolias are described as extremely demanding trees and bushes when it comes to soil moisture and nutrition. The consequence of this attitude has been that they have been limited to favourable garden and park environments where, with their exceptional seasonal qualities, they have contributed to the great appreciation of this group of plants. When one later studies how many species of magnolia grow in their natural habitats, one realises that they can cope with a considerably warmer climate than has previously been believed. One interesting fact is that during their evolution, these isolated populations of magnolias in particular have developed in this warm climate and there evolved unique strategies to manage these conditions. During tests in which botanists have subjected the trees to stress from for example warm, dry conditions, these genotypes are much tougher than those originating from cool, damp environments. In earlier work on selection, botanists have not bothered to analyse this perspective, but with future challenges like for example a warmer climate, this perspective will be crucial.
The Japanese bigleaf magnolia (Magnolia obovata) is nowadays not an unusual tree here in Sweden. We know that it will develop successfully, and with its broad leaves and fragrant summer blossoms it is a wonderful ornament for parks and larger gardens. The species is impressively distributed in Japan – from Kyushu in the south to Hokkaido in the north, as well as the Kuril Islands in eastern Russia, north of Japan. For this study expedition, we chose the Japanese bigleaf magnolia specifically for its wide prevalence and also because it grows in many different types of climate. This makes it interesting to evaluate and to investigate the possibility of finding a more suitable type for a future climate. In its natural habitat, it occurs in fantastically lovely forest environments with a unique diversity of other truly valuable trees for cultivation, such Stewartia, maples, firs and cherry trees.
The willow-leafed magnolia is nowadays a relatively unusual species that can mostly be found in exclusive plant collections and botanical gardens. Despite being unusual in Sweden, it is an intriguing species with great potential. Among the most common spring-flowering magnolias cultivated in Sweden, it is first and foremost the Japanese kobus or kobushi magnolia (Magnolia kobus) with which we have most experience. The willow-leafed magnolia flowers like the kobushi magnolia with white blossoms on bare twigs, early in the spring. The difference is that the willow-leafed magnolia starts flowering earlier in its youth and often develops into a shapelier tree than the kobushi magnolia. Trying to find a magnolia tree that not only delivers a lovely spring flowering but is also decorative the rest of the year with a growth resulting in a fine shape is something that we are especially interesting in at Botaniska. That may also bring greater recognition to magnolia trees than for just being a spring-flowering tree.
During the field expedition in 2018, many different forest populations with willow-leafed magnolias were studied. The aim was partly to find populations that grow under conditions that make them valuable to cultivate under Swedish conditions, and partly to study the species' natural growth system. In that way we can learn more about how these trees want to grow and which demands and limitations they have, which is crucial for how we should cultivate them successfully in the Botanical Garden or anywhere else.
Magnolias in the Botanical Garden
Botaniska currently has an impressive collection of magnolias from North America as well as East Asia. Magnolias are one of nature's most spectacular plants with a flowering and leaf structure that are unmatched, and there are finely developed trees and bushes in several places in the Garden and Arboretum. After this study trip, we hope that we can develop the Garden's collection of magnolias even more, and in that case with a genetic material that truly belongs to a tree of the future.