The So-called Pioneer Species

Michael Boßdorf is the director of the state-run gardens of the Hessen-Kassel Museumslandschaft, an association of regional museums. His responsibilities include the Auehang, where our trail is located. At first he is, understandably, rather unenthusiastic about a dirt trail being laid here. We agree that the trail shall not be authorized as if it were an official route and that visitors are to enter at their own risk. We meet on the street “Schöne Aussicht.” It's raining and hailing, and he tells me of the transformations the Auehang has undergone and the challenges of making rubble blossom.

Michael Boßdorf in conversation with Natascha Sadr Haghighian, Kassel, 2012
Natascha Sadr Haghighian: Mr. Boßdorf, can you briefly describe the planting concept for the German Horticultural Show of 1955?
Michael Boßdorf: What happened first is that the hillside was filled in with around two million cubic meters of debris after the war. Then, when it was certain that the 1955 German Horticultural Show would take place here, this bluff, filled with debris, underwent preliminary preparations, meaning it was pulled further out toward the park; or in other words, the hillside’s form was changed, becoming flatter. This was done primarily with debris from the old part of the city, from Kassel’s city center, also with a certain percentage of clay, brick, and sand. How to plant vegetation on it was indeed a big problem. The next thing to think about was how to lend the slope firmness so as to avoid a landslide, because this debris, especially in the lower areas, had a thickness of several meters.
Can you explain which problem arose while planting?
The problem was that the debris, due to its thickness, definitely has an immense drainage effect. That means precipitation drains right through the underground layers. The plants, no matter if they’re woody plants—trees or bushes, or also the so-called herbaceous layer, perennial shrubs—they wouldn’t be able to access any water. That’s a big problem, as is the stability of the slope itself. Therefore the first considerations focused on how we could lend it stability, and what kinds of woody plants can even endure this stress. And the answer was to plant the so-called pioneer woody species. Then we also filled the lower areas of the slope a little bit with topsoil, and the amounts we needed weren’t available at all: finally we really had no more than thirty or forty centimeters. Then this was sown with clover, with Lucerne and with legumes so the slope would green and maintain a certain stability, and so its capacity to hold water would improve and stabilize too.
And these pioneer woody species, as they’re called, were primarily birch, black locust, ash, maple, shrubs like privet and yew. That’s what was planted here. In the Rosenhang area, a total of 140,000 woody plants were planted. Of course, at first they were all quite small plants. Then they grew to a certain size by the time the Horticultural Show came in 1955, but they were still relatively small. Then over the course of several years, decades afterwards, some plants were removed, which was urgently needed to let the individual plants experience good development, or so their so-called habitus could develop, so the structure of the slope could materialize. That means that over the course of decades plants were removed time and again. It was nevertheless a big problem to always keep the slope stable, and so in recent decades the slope has undergone stabilization measures repeatedly. Tree trunks have been embedded in the slope and stabilized to prevent landslides. Then we kind of had a big problem with rabbits that were undermining the slope, or eroding it.
The whole slope was conceived as a terraced garden while the Karlsaue was in planning. Is that right?
That’s right. And that’s a reference to the baroque era under Landgrave Karl. The area which is the Ehrenmal [cenotaph] today was the so-called Prinzess-Garten, a terraced garden that has, for the most part, kept its original form to this day. And in this terraced garden, in this Prinz-Georg-Garten, there were also lemon, orange and fig trees. Attempts were made at growing wine there, because the location has great exposure to sunlight. None of this exists in that form today because it would be much too elaborate and expensive. And other than that, the so-called Rosenhang, which stretches from the little temple, the so-called Früstückstempel, to the Ehrenmal with its large dimensions, was a relatively steep slope before the BUGA [German Horticultural Show] of 1955, and it was also laid out as a terraced garden.
Apart from the roses and exotic plants, did the new concept for the distribution of plants throughout the park incorporate these original aspects? Was it more about showing exotic plants? Is it possible to say something about how the planting in general was?
The Rosengarten was integrated into the overall concept of the 1955 Horticultural Show. That was done by Professor Hermann Mattern, the landscape architect, who was in charge of carrying out the design here. He oversaw the construction and realization. The Rosenhang in its entirety in this area of the park was integrated into the 1955 BUGA. And even modelled too. The park area all the way down to the Little Fulda was correspondingly modelled, and the realization of the modelling of the terrain was quite successful. The pedestrian traffic pattern was then adapted and developed, for which we used a lot of sandstone: partly in the bordering of the paths, and in the retaining wall in the so-called frontal Rosenhang area, which today is between the cenotaph and the documenta-Halle. Many hours were spent planting there. Lots of roses too. A total of 12,000 roses were planted for the BUGA ’55. There aren’t anywhere near that many today, an effect of the bad soil conditions that I told you about earlier: water and nutrient storage isn’t happening. Roses need significantly richer soil, nutrient-rich soil, and that’s unfortunately not the case here on the Rosenhang. But during the BUGA ’55 and a few years after that, too, this place was resplendent in exquisite roses and shrubbery. And today we’re making efforts to conserve this area right between the Ehrenmal and documenta-Halle in its original form with lots and lots of shrubbery—there was a lot of blossoming shrubbery in the mix—and with roses, even with historical roses that we had here in 1955.
And that’s our goal at the moment. We’re also making efforts to conserve the population of woody plants in its 1955 state, and expand it too in the area of the so-called rear Rosenhang, between Ehrenmal and temple. But also to conserve or regain the view of the park and of the open landscape by creating forest aisles and open vistas for the visitors up here on Schöne Aussicht in Bellevue, because that’s also one of the old magnificent streets of Kassel from baroque times. People enjoyed strolling along this street, Schöne Aussicht, getting a wonderful view over the park to the Orangerie and into the open landscape.
Could you briefly describe what kinds of vegetation grow on this slope now?
At the moment, there’s a high percentage of box and yew. And then there are cherry trees, oaks, linden trees. As far as shrubs go, we have privets and also some cherry laurel. Then the wild gooseberries (Ribes and also Lonicera), the honeysuckle, and in some areas also barberry. Some hazelnuts too. There’s also the occasional oak tree up here on the slope.
Which of those are the pioneer species that you mentioned earlier?
Most of them can be counted as pioneer species, but not the box, or the cherry laurel either. But the Lonicera can—they were planted back then, too, as were the hazelnuts. Cherry trees can’t really be called pioneer plants, but all the others can.