Every tree a point on the world map

Forstbotanischer Garten Tharandt

Ulrich Pietzarka

Winter at Forstbotanischer Garten Tharandt is over. The park opened to the public again at the beginning of April. Here, you can walk through forests as they used to be – and as they one day may become.

You do not necessarily have to book a long-haul flight to visit the Rocky Mountains. From central Dresden, they are just two stops away on the S-Bahn. Ulrich Pietzarka, warden of the Forstbotanischer Garten (Forest Botanical Garden) for the past 24 years, is waiting for us at the station in Tharandt.

The 35-hectare site was planted in 1811 by Heinrich Cotta who ran it as a private forestry college. It has since been taken over by the Faculty of Environmental Sciences at TU Dresden. More than 3,000 different tree species grow here, only a few of which are actually native to Central Europe.

A sculpture of Heinrich Cotta, one of the pioneers of scientific forestry. © Ulrich Pietzarka

We are taken by car to the other side of this small town, which was a fashionable spa resort in Cotta’s time (celebrity guests included the German literary giants Goethe and Kleist). We pass under a long, narrow bridge that divides the garden into two sections: the historic and the North American, at the gate of which we now stop. According to the map, the left turn will take us to Utah and Nevada, the right to Georgia.

Over the past few decades, Pietzarka has travelled extensively in the USA, studying the forests there and collecting the seeds of local tree varieties.

A totem pole at the entrance to the park’s North America section. Here grow trees that are not native to Central Europe. © Ulrich Pietzarka

The subject of Pietzarka’s research is the forest of the future. That’s because forest terrains will have to adapt to climate change. Heat and drought are forecast to increase, including here in Central Europe. Pietzarka and his colleagues at TU Dresden are therefore looking for alternatives to the trees that have traditionally dominated the German landscape. “We are studying the behaviour of domestic varieties, for example how they react to drought.” He currently has high hopes for some types of oak and ash which he believes could make the German forest future-proof.

It is early April, and blossom is beginning to appear. However, the group of trees in front of us looks sad and distressed. “Juniper which hasn’t survived the winter.” So not a candidate for the German forest of the future.

Halesia carolina is a shrub native to the southern USA. It is commonly called silverbell or snowdrop tree since its blossoms look very similar to snowdrop flowers. © Ulrich Pietzarka

A few hundred metres further on is a rocky crag, from the top of which the surrounding villages are visible. “Our Rocky Mountains,” Pietzarka explains with an ironic smile. The crag is not particularly high, but it offers a panorama of the different trees.

The researchers know the origin of each individual one; after all, they have collected their seeds by hand in China, Russia and in the USA. The locations of the mother trees are recorded in a database. “Each of these trees is a point on the world map,” says Pietzarka.

The park has its own Great Lakes. Here blooms Cercis canadensis, a tree native to the USA, Canada and Mexico. © Ulrich Pietzarka

A few hundred metres further on, the New England section begins. A display board shows a picture of the Indian summer: the brightly coloured crowns of sugar maple, red maple and red oak. “That’s where we’re going,” says Pietzarka. “To that jumble of trees. The German forest is too structured, too ordered, which makes it vulnerable to pests. In monocultures, they can spread very quickly; all it takes is for one beetle to land on the branch of a neighbouring tree. But if it has to fly a hundred yards to find the next tree of the variety, that’s too much of an effort.”

Acer rubrum, the red maple, is most impressive in autumn colours. © Ulrich Pietzarka

On the way back to the car, we pass a sign pointing to giant sequoia trees. The trees behind it are really pretty – but giants they aren’t. Pietzarka laughs. He collected the seeds in 1999 in the Sierra Nevada but didn’t plant them here until in 2003. It will be several decades before they live up to their name.

Many of the results of the research being done here in the Forstbotanischer Garten will only become available to future generations. “A forest generation takes about 100 years,” says Ulrich Pietzarka. “In their terms, a cycle of ten or 20 years is nothing.” But if he didn’t have the patience, he wouldn’t be in the job anyway.

Forstbotanischer Garten Tharandt, Am Forstgarten 1, 01737 Tharandt. Open daily from April to October.

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