Some Symphytum hybrids in Belgium and the Netherlands. (1971) Cytotaxonomic studies in the genus Symphytum, 3. Crossing experiments between Symphytum officinale L. (1969) Cytotaxonomic studies in the genus Symphytum, 2. (1990) Hybridization in Symphytum: pattern and process. (1983) Cyto- and chemotaxonomical studies on the sections Officinalia and Coerulea of the genus Symphytum. (1978) Variatie en hybridisatie bij enkele taxa ven het genus Symphytum. (1990) Quelques observations floristiques effectuées à proximité du château de Houx (Yvoir, province de Namur, Belgique).

Untersuchungen an Überwiegend norddeutschen Pflanzen der Arten S. (1972) Cytotaxonomische Untersuchungen an der Boraginaceen - Gattung Symphytum L. It has sky-blue corollas, unwinged stems, a smaller calyx (3-5 mm), distinctly reticulate, dull nutlets and is very hirsute hairy (see Lambinon & Verloove 2012 for additional characters and its separation from S. Pure populations of Symphytum asperum may be very rare in Belgium at present. All these (notho-) taxa intergrade and specific limits have become obscure in Belgium. officinale is also present (as usually is the case). On the basis of herbarium collections (for instance from Zeebrugge) we have been able to prove that pure stands of Symphytum asperum ultimately change in stands of S. asperum and its back-crosses with native S. Symphytum x uplandicum is here treated in a very broad sense as to include S.

It was formerly cultivated for forage but some populations probably arose as a result of a spontaneous hybridization between native S. Symphytum x uplandicum is a fertile hybrid. Occurrences on dumps and waste land are nearly always ephemeral. Known for instance since at least 1950 from Oudergem (Zoniënwoud), since 1974 from the nature reserve De Fonteintjes near Zeebrugge,… As a naturalized alien Symphytum x uplandicum is most often found in ditches and road verges.

Several other locations are also well-documented. Known since 1884 from the surroundings of Leuven (Korbeek-Loo, Pellenberg) and still present in the valley of river Dijle at present (Verloove 2002, 2006). officinale) (SW-As.) – A rather rare, locally naturalized escape from cultivation (formerly introduced for forage, more rarely as an ornamental).