In 2017, a number of expeditions to Georgia and the southern Caucasus were undertaken by Henrik Sjöman, one of Botaniska's scientific curators. The aim was to study the fantastic diversity of astonishing trees and bushes there of great value in cultivation. Field expeditions were carried out in cooperation with researchers and gardeners from Tbilisi Botanical Garden and Tbilisi University.
The Caucasus mountain range is almost like a link between Europe and Asia, on account of its situation between the Black Sea and the Caspian Sea. Many European species have their easternmost habitat in this region while it is the westernmost habitat of many Asian species, which makes the region very rich in species and also unique.
The high altitude of the mountain range, with summits over 5,000 metres above sea level, means that many different types of vegetation system exist here and can be experienced – from alpine meadows above the tree line in high terrain to hot steppe forests at lower altitudes. The climate varies enormously in Georgia even from east to west – from subtropical conditions near the Black Sea with tea plantations on the hillsides to desert regions in the country's eastern regions.
This variation in climate makes Georgia one of the regions in eastern Europe with the greatest wealth of species. The climate is of course influenced by how far from the Black Sea or how high above sea level one happens to be.
At the Botanical Garden in Gothenburg, intensive work is being carried out on the study of plants that in their natural habitat experience partly the conditions that we already have in Sweden, and partly those that we risk experiencing in the future, since much indicates that the climate is going to become warmer and drier.
By studying natural plant habitats in climate conditions that may be our future climate, it is possible to see which species and which genetic material from trees and bushes for example we should start learning to make use of and cultivate.
Before the field work in Georgia could be started, various calculations were carried out and data models constructed that showed where in Georgia and the southern Caucasus we can already find what may be the future climate in Sweden and western Europe. Based on these calculations, key regions could be identified where we later undertook field studies. There we studied species and ecotypes that had naturally developed the capacity to flourish under these relatively tough conditions and also to grow into beautiful plants that are sustainable in the long term.
The main aim of the project was to study which trees from Georgia may be suitable as city trees in Sweden and western Europe. According to the calculations mentioned above, studies have been carried out first and foremost in warm, dry steppe forests in central and eastern Georgia. The forests there experience warm, dry summers and really cold, dry winters – conditions that are almost identical with the inner-city environments of today and the future in for example Gothenburg or Stockholm.
In these warm steppe forests we can partly find well-known species like the European or common hornbeam (Carpinus betulus) and Cornish oak (Quercus petraea), and partly more unusual species like the Caucasian zelkova (Zelkova serrata), the Oriental hornbeam (Carpinus orientalis) and the Caucasian hackberry (Celtis caucasica). Studying and possibly collecting already well-known species, whether cultivated or growing wild in Sweden, is important since the genetic material of the common hornbeam for example is of another genetic origin in Georgia than it is in Sweden. The genetic material from Georgia has developed strong strategies for coping with warm and at times really dry conditions, which our Swedish material has not needed to do. Much of the work that is being done today concerning the selection of future trees is about finding genetic material with the right origins.
The Caucasus in Botaniska
Currently there is a large and impressive collection of plants from the Caucasus in the Garden. They come from many earlier collecting expeditions and seed exchanges with botanical gardens from that region. When we see these plants flourish in the Garden, we realise that the Caucasus is a territory that can deliver many fine, much valued plants to Swedish gardens. We hope that we can develop the collection even more in the future, and also see smaller tree populations in the Arboretum with their origins in Georgia and the Caucasus.