Nadwiślanka sour cherries
Also called słupska or słupianka from the name of the place where it had been planted first: Słupia Nadbrzeżna. It is a juice-type sour cherry. It used to be transported by water between Sandomierz and Warsaw, where it was enthusiastically received. Its success was mainly due to high parameters: extract and acidity. They make it perfectly fit for manufacturing sour cherry concentrate which yields a more intensive colour and aroma from lower fruit quantity.
This sour cherry variety is uniformly claret-coloured and smaller than traditional cherries. The size ranges between 12 mm and 20 mm, depending on tree age and position. The fruits are round, juicy, slightly flattened. The colour does not change even after processing. The taste is characteristic of sour cherries: slightly sour, but intensive.
Nadwiślanka sour cherry trees bear fruit irregularly due to low resilience to frost in spring. Yet, they are very resilient to diseases. Depending on the substrate, the trees grow for 25 to 100 years.
Where to buy: http://www.trzyznakismaku.pl/produkty/wisnia-nadwislanka
Source of information: http://www.minrol.gov.pl/Jakosc-zywnosci/Produkty-regionalne-i-tradycyjne/Lista-produktow-tradycyjnych/woj.-swietokrzyskie/Wisnia-sokowa-nadwislanka