Skadi Menne

Application of Sphagnum mosses

A field report from the University of Heidelberg

One of our first customers to receive Sphagnum mosses for spreading from our Sustainability Team was the University of Heidelberg. In the botanical garden of the Ruprecht-Karls-University, a peat moss basin was established in 2019/2020. Mr. Andreas Franzke, who is responsible for the project, gave us an overview of the current status in an interview.

Kpoint: Hello Mr. Franzke, thank you very much for taking the time. How large is your peat bog area and how can we imagine the construction of the area?

Andreas Franzke: The basis of the plant is a sealed concrete basin, which measures approx. 15 x 9 meters and has a depth of 0.5 meters. The base is made up of inverted PE plastic boxes that have been drilled through and now serve as a water reservoir for the peat body. The boxes are placed at a distance of 10 cm from each other. Coarse white peat was placed on top of the boxes and in the spaces between them. On top of this, two higher, relatively large bulk areas were modeled with fine white peat.

In this layer above the boxes the peat body is about 20 to 25 cm thick and the bulbs have a total thickness of about 50 cm. The structure was then allowed to settle for about 9 months before the area was planted. In the middle we have what is called the “bog eye”, which is a completely free area filled with water. This was edged with peat bricks to prevent the edges from slipping and to keep the bog eye clear.

Skadi Menne: How was the Sphagnum moss spread?

Andreas Franzke: The Sphagnum mosses were evenly distributed on the modeled peat layer and pressed on a little. Over the winter, the area was covered to protect it not only from the cold, but also from the leaves.

Skadi Menne: How have the mosses we supplied developed?

Andreas Franzke: The Sphagnum mosses have developed positively throughout. In addition, the following species have emerged from the soil seed bank: ‘Middle Sundew’, ‘Round-leaved Sundew’ and ‘Bell Heath’. These have all become firmly established in the plant and are forming good stands. That’s also exactly what we wanted to achieve.

Skadi Menne: What kind of irrigation system do you use?

Andreas Franzke: The basin does not have a drain. So irrigation is done exclusively by rainwater. On days without rain, the basin is irrigated once or twice via circular sprinklers with rainwater from a cistern, an underground or covered collection tank.

Skadi Menne: Looking back, what experience have you gained in planning, creating and maintaining the area?

Andreas Franzke: One important point is the removal of any weeds. So that we can distribute the weight evenly during removal and not leave any permanent imprints in the soft subsoil, we have laid out a ladder as a footbridge, with a board as a support. This prevents compaction of the peat bodies.

Some of the plants that belong in the system must be regularly reduced in population or replanted in the desired areas of the peatland. ‘Bell heather’ and ‘blue moor grass’, for example, are so vigorous in growth that we have to “trap” them regularly. More demanding species, such as ‘Middle Sundew’ or ‘White Beak Reed’, on the other hand, have already become firmly established in the designated places.

When it rains too much, the water level has to be lowered by means of a submersible pump. This is time-consuming, as the pump regularly becomes clogged. Probably an adjustable drain would be good to avoid clogging in the future. In winter, the water level is not regulated. Too high water levels in the winter will result in drowning of unwanted weeds in the low areas. We have not yet observed any disadvantage for the bog planting in this context.
In retrospect, the planting of the raised bog basin has actually developed as planned. Since we had no previous experience in this area, this is of course particularly gratifying for us.

Skadi Menne: Thank you Mr. Franzke for taking the time for this interview!

If you should ever visit Heidelberg, you can of course visit the Botanical Garden at any time. You can then see on site how well our Sphagnum mosses have developed, and you will find even more information about the installation there.

(Photos: S. Elfner Botanischer Garten Univerity of Heidelberg)