Kalkaster (Aster linosyris L.), een inheemse soort in Nederland

Goldilocks aster (Aster linosyris) was presumed never to be observed in its natural biotope in the Nether­lands. During an assessment of Mountain germander in the Netherlands, however, we stumbled upon a vegetation recording made on the 23rd of May 1950 by Victor Westhoff, mentioning Aster linosyris on a chalk ridge in the Popelmondedal at the Sint-Pietersberg, Southern Limburg. Goldilocks aster is a yellow composite characterized by up to 50 cm stems that are densely packed with rugged linear leaves. The species has disciform flower heads which are arranged in plumes. It occurs mainly in central and southern Europe, in calcareous grasslands, and is particularly drought resistant. The recording of Westhoff describes a vegetation characteristic for the Cerastietum pumili, including very rare species for the Netherlands such as Helianthemum nummularium, Veronica triphyllos, and Moenchia erecta, the latter is now extinct in the Netherlands. In the Netherlands, no earlier observations of Aster linosyris are known although white cultivars of the species are described from the area of Zeist (Province of Utrecht) and Middelburg (Province of Zeeland) at the turn of the 20th century. Since the 1960s, the species has been removed from Dutch species lists. Westhoff’s record describes a vegetation bordering a limestone grassland of the Festuco-Brometea, the natural habitat of Aster linosyris. Old maps and vegetation recordings of the area support the occurrence of this now locally mostly disappeared vegetation type. Moreover, observations of the species within seven kilometers from the Popelmondedal near the village of Wonck in Wallonia, Belgium, supports the plausibility of this first and last sighting of Aster linosyris in the Netherlands. As climate conditions are becoming more favorable for the species, however, it is not unlikely the species will colonize to the south of Netherlands again, although dispersal might be a serious obstacle. Therefore, we recommend a return of the species on Dutch species lists as an indigenous species for the Netherlands.