Biological flora of Central Europe: Dactylorhiza sambucina (L.) Soó

Dactylorhiza sambucina (L.) Soó is a polycarpic perennial herb occurring in the Central European, Eastern European, and Balkan floristic provinces. At the European scale, the IUCN considers it a species of "least concern". This paper reviews the taxonomic status, morphology, distribution, habitat requirements, mycorrhizal associations, and life cycle of D. sambucina, with special emphasis on its reproduction. We also summarize information on chromosome numbers and genetic variation. Our data from 12 years of monitoring D. sambucina in the Czech Republic show that three to four leaves have to be produced prior to flowering; plants with five and more leaves flower regularly. Juvenile plants near adult plants suggest recruitment from seeds. About 20% of our 450 monitored plants underwent dormancy (failure of mature plants to produce above-ground parts in one or more growing seasons), the maximum duration being eight years. After reappearance, these individuals were usually sterile for the next year. Mortality was highest (24%) at the seedling stage. Regarding the purple/yellow flower colour polymorphism that characterizes D. sambucina, we found no correlation between morph frequency and soil properties (pH, calcium content), population density, or altitude above sea level.