The species occupies multiple large areas in undeveloped zones of Mount Auburn Cemetery. It apparently is naturalized on the cemetery grounds. There is currently no documented evidence that this Old World species is truly naturalized in a natural habitat in New England or in fact anywhere in North America. However, in Europe (Belgium) there has been observed a recent rapid spread of naturalized populations: the first one was detected in 2008, and by 2020 there were already 37 populations reported. (W.F.Nichols, A.Schori, A.Lamb, A.Haines 2022, Rhodora 2020, issued March 31, 2022, Vol. 122, No. 992, p. 332-335).