Die Elsbeere (Sorbus torminalis) – Königin der Wildfrüchte


This project, as part of a dissertation on floral biology of the wild service tree, provided the following results: 1) The wild service tree Sorbus torminalis of the Rosaceae family either grows as a solitary deciduous broad-leaf forest tree, mainly in France (Alsace) or Austria (near Vienna), or in orchards as a spur grafted on dwarfing quince rootstock. 2) The white self-fertile flower aims at the widest possible range of potential pollinators and offers easy access to tits nectar. The nectar has two distinct smells, one of honey, which attracts bees, and one of rotting material, which attracts flies. The anthers contained ample fertile pollen, a pre-requisite for effective pollination, but also for solitary bees, who spend most of their time collecting pollen, which is mixed with a small amount of nectar as food supply for their young. In the present experiment, Sorbus t. pollination was by bumble bees, honey bees, solitary bees, except for the solitary Osmia bees, possibly due to lack of nesting structures. 3) A local pollination experiment in the Bonn region showed the greatest number of seeds per fruit, as a measure of the pollination success, with manual cross-pollination. The pollination success rate of the free blooming control flowers, to which the flower visitors had free access, was similar to that of the manual self-pollination. This suggests there was a limited supply of pollen, probably caused by insufficient pollinators, although a total of 88 species was counted on the flowers. 4) The red-brown, cherry-sized fruits are difficult to pick from the large solitary trees by long ladders. The fruits contained up to five seeds, responsible for the marzipan-like taste on fruit processing. Due to the astringent taste of the fresh fruit, they might be more suitable for bread spreads, preserves, jam, distilling into brandy and dried fruit for a healthy snack. 5) Challenges of Sorbus torminalis cultivation include a) determination of the optimum harvest date (OHD) and uniform maturation, b) rootstock selection for dwarfing and early yield and c) countermeasures against alternate/biennial bearing. 6) Advantages of Sorbus torminalis cultivation include tolerance to frost in the winter and to drought in the summer and hence climate resilience and increase in biodiversity.