First report of Solidago altissima in Belgium
The genus Solidago (Asteraceae) is predominantly a North American genus of approximately 120 species. In Belgium, two species, Solidago canadensis and S. gigantea (both EPPO List of Invasive Alien Plants) are widespread non-native species, where the latter is the most frequently observed. S. altissima had previously been recorded in some parts of Europe but further investigation shows that the records were actually S. canadensis. In July 2016, a small population of Solidago was discovered in a nature area ‘Verrebroekse Plassen’ in the Waasland port area in Beveren (Belgium, province of East Flanders). Morphologically the specimens were similar to S. canadensis, however, the plants were unusually tall (over 200 cm) with stiff stems. Flowering of these plants started late in the season (October to early November) compared to S. canadensis, which flowered several weeks earlier. In order to identify this population, nuclear genome size was measured by cytometry and compared to S. canadensis. The results show the population in Belgium to be distinct to S. canadensis. In addition, plants were shown to be hexaploids with an estimated chromosome number of 2n = 54 where only diploids (2n = 18) are known from S. canadensis in Europe. These findings, coupled with morphological characteristics support the identification of the plants as S. altissima – representing the first confirmed identification of the species in Europe.
Sources
Verloove F, Zonneved BJM, Semple JC (2017) First evidence for the presence of invasive Solidago altissima (Asteraceae) in Europe. Willdenowia 47, 69-75.