Euphorbia oblongata Griseb. (SE-Eur.) – A very rare alien, most probably an escape from cultivation. A single plant of Euphorbia oblongata was discovered in woodland in Roeselare (Sterrebos) in 2008 (later confirmed but now gone). It grew in half-shade by a ditch. Its origin is obscure: the Sterrebos is an old park (with, among others, long-established populations of Euphorbia dulcis and Trachystemon orientalis) but E. oblongata appears to be a recent, independent introduction. Since 2011 a small population of Euphorbia oblongata also persists by river Schelde in Eine (Oudenaarde). This species is, surprisingly, not mentioned by Carter & Cullen (1997) and Jäger & al. (2008) although a garden origin seems most likely.
Euphorbia oblongata is a poorly known species (see also Barrett 1996). It is one of the few species with 2(-3) cyathial glands (4 in nearly all widespread species in Eurasia). It furthermore usually has densely pubescent stems (although nearly glabrous forms also exist).
Similar plants have been recorded by a ditch in Brugge around 2000 but the population was destroyed soon afterwards (and voucher specimens are lacking).
Barrett D. (1996) Euphoria oblongata Griseb. in S.E. Hampshire (v.c. 11). BSBI News 71: 46-48.
Carter S. & Cullen J. (1997) Euphorbia. In: Cullen J. & al. (eds.), The European Garden Flora, vol. 5. Cambridge University Press, Cambridge: 81-101.
Clement E.J. (1979) Adventive news: 14. Euphorbia oblongata Griseb. in Britain. BSBI News 22: 16-17.
Jäger E.J., Ebel F., Hanelt P. & Müller G. (eds.) (2008) Rothmaler Band 5. Exkursionsflora von Deutschland. Krautige Zier- und Nutzpflanzen. Springer Verlag, Berlin: 880 p.
Petch C.P. (1979) Euphorbia oblongata. BSBI News 23: 26.