Harmas KGV experimental setup
Harmas KGV is a model experiment to investigate the relationship between the microclimate in a specially designed dry garden and the growth of twenty highly endangered native wild herbs.
Plant
On the area of plot 3, a stone fill was made with local Pläner limestone, which rises towards the center. Aligned in a north-south direction, the site offers slightly inclined slopes in all four directions. There are considerable temperature differences between the north side, which receives the least amount of sunlight, and the south side, which receives the most. This effect is intensified by the centrally towering exhibition pavilion and the buildings to the east, which provide additional shade for the areas with the least exposure to the sun.
East-facing slope June 2021 to October 2022
South-facing slope June 2021 to October 2022
Hillside location west June 2021 to October 2022
Hillside location north June 2021 to October 2022
Species
The species list was not compiled with regard to one of the classified plant communities such as calcareous grasslands, as many of the species can occur in both dry and semi-dry grasslands. The plant community shown is thus constructed and can be characterized as a thermophilic plant community on alkaline ground. The species require light and warmth. Once the plants, which are very drought tolerant due to adaptation (for competitive reasons), have grown in, they are no longer watered, and self-settling species are weeded in the experimental site. This reduces the pressure of succession and prevents the threat of scrub encroachment, both of which are causes of the disappearance of the plants cultivated in the Harmas KGV in the field. another consideration when compiling the species list was the future care of the plants by non-professionals, which requires a certain reliability of the selected plants. A long flowering period was also important, so that flowers can be found in the dry garden from spring to fall. Care was taken to alternate low and cushion-forming plants with taller plants. Some species form very deep roots, others do not.
Evaluation 2020 to 2022
2021
Evaluation of the number of individuals depending on climatic conditions compared to the planting of 29.9.2020. Overall, the impression was more lush than expected, which can be attributed to the heavy rainfall during the 2021 growing season.
Northern slope location
The conspicuously good growth in the sunny areas (north) is due to the fact that the highly competitive species particularly benefited from the high humidity. The meadow sage in particular was conspicuously vigorous and better seeded than in the other areas. However, two species on the north side that were still present on the others have completely disappeared: Field stonecrop and sand thyme. These two less competitive species were unable to benefit from the damp conditions and were displaced. In the case of the sand thyme, it was already taken into account at the time of planting by placing it on the upper edge of the slope that it has a low growth rate and special light requirements. However, the backfilled substrate layer there was thin and the underlying rock fill led to particularly strong water drainage, so that the sand thyme was not able to grow particularly well there. The fact that the field stonecrop failed here is due to the fact that the other species grew so strongly due to the moisture that it lacked the light.
Eastern slope
With the exception of the sand thyme, all species were present and well developed here. However, it was striking that the field stonecrop was very well developed here and even seeded. One reason for this may be the stronger sunlight compared to the north side. The steeper slope on the eastern side also leads to increased water drainage, which had a moderating effect on the highly competitive species. The drought-tolerant field stonecrop therefore had a chance to develop.
Southern slope
Although all species were present on this side, they were consistently less vigorous than on the comparison plots. The meadow sage in particular was well developed and heavily seeded. Both the field stonecrop and the sand thyme had no problems here. Due to the strong sunlight, the Carthusian carnation was also unable to utilize the available open spaces at this exposed location. It prefers the more moderate locations in the east and west.
Western slope
All species were present, some of them very vigorous. The meadow sage was also heavily overgrown.
2022
As 2021 was the year of growth, 2022 is the first year in which the differentiated requirements of the individual species come into play and development trends can be observed. The difficult start for the sand thyme has already been described in the 2021 report. As a light- and heat-loving species, it apparently only has optimal conditions on the south side. After losses in 2021, three young plants were even registered here in the following year.
Compared to other species, the common dost is less heat-tolerant. This species, which is so attractive to insects, developed best on the north side and only increased its population slightly there. In 2022, it significantly increased its population on all areas except the south side.
As a very light-demanding species, the field stonecrop was no match for the competition on the north side in 2021, but was present on the other areas. However, as it is a relatively short-lived and rapidly seeding species, the field stonecrop was able to take advantage of the dry year 2022 and spread to all areas and even reappear on the north side. The field stonecrop was originally selected because of this ability to quickly fill in gaps where they occur.
The Carthusian carnation requires a lot of light for optimal development, but tolerates extreme heat less well. For these reasons, the number of plants on the north side decreased in both years. However, there was also a slight decline on the south side in the significantly warmer and drier year 2022. The Carthusian carnation apparently feels most at home in the more moderate conditions on the east and west sides.
The rock cinquefoil also simply lacked light on the north side. In contrast to the Carthusian carnation, however, it copes better with high temperatures, which even led to a slight increase on the south and west sides in 2022.
The two grasses Festuca valesiaca and Melica transsilvanica are among the most competitive species. They have been able to establish themselves well in all areas and have also proliferated. In future, care will have to be taken to ensure that they do not displace less competitive species.
Evaluation 2023
09.07.2023
Mapping, Sylvey Lommatzsch, Helga Petzold, Sabine Kroehs, Robert Thiele, Nana Petzet.
9:00 – 11:00: Weeding (Agrostis capilaris, bindweed, Meliotus lupulina, dandelion)
11:00 – 16:00: Team Sabine and Sylvey map east and south slope, Team Helga and Nana map north and west slope, Robert documents spatial distribution separately
10.07.2023
Removal: Criteria for case-by-case decision of competitive species such as Melica and Scarbiosa are removed where they crowd out non-competitive species such as Liliago and Thymus. Diversity has priority. The removal is documented.
Thanks to
A team consisting of Helga Petzold (TU-Dresden, head of Boselgarten), Sabine Kroehs (landscape gardener, Artenreich), Sylvey Lommatzsch (allotment gardener, painter) together with the artist Nana Petzet took over the observation of the plants and recording of the data since 2020. Ralph Teckentrup and Sven-Karsten Kaiser from the allotment garden association Flora I e. V. took over the photo documentation since 2020 and, together with Heike Heer, the monitoring of the horticultural maintenance.