Lonicera chrysantha Turcz. ex Ledeb. (NE-As.) – An exceptional escape from cultivation. A single shrub was recorded in spontaneous woodland (probably bird sown) near motorway R8 in Bissegem (Kortrijk), along with Lonicera xylosteum.
Lonicera chrysantha belongs to a difficult species complex that also includes native L. xylosteum. From the latter it is best distinguished by larger corollas and leaves that are more acuminate at apex. Confusion is also likely with the highly invasive Lonicera maackii (Rupr.) Maxim. and furthermore with L. morrowii A. Gray and L. ruprechtiana Regel. All these species are rather frequently cultivated in our area. The former is readily told apart by its short inflorescence stalks that do not exceed the leaf stalks (less than 5 mm long). Lonicera morrowii, also known as an escape in Belgium (see there), has an upper corolla lip that is divided to base, a glabrous ovary, a shorter inflorescence stalk (usually not exceeding 15 mm) and its stamens are entirely glabrous. In Lonicera chrysantha, in contrast, the upper corolla lip is divided at most for half its length, the ovary is somewhat glandular, the inflorescence stalks longer (usually 15-25 mm long) and the stamens are hairy in the lower half. Lonicera ruprechtiana is also exceedingly similar but its ovary and corolla are glabrous (corolla densely pubescent outside in L. chrysantha). Lonicera chrysantha itself also is a variable species. Lonicera koehneana Rehder is sometimes given species rank (e.g. Li 2000) but it was recently subsumed under L. chrysantha (as var. koehneana (Rehder) Q.E. Yang & al.) in Flora of China (see Yang & al. 2011). The plant from Kortrijk possibly belongs with Lonicera chrysantha var. chrysantha although it surely is less typical than authentic Asian material. It is possible that plants in cultivation rather represent (fertile?) hybrids between Lonicera chrysantha and L. xylosteum. Both species may well be conspecific and have been united in the past.
There are very few other records of Lonicera chrysantha in the wild in Europe (although it might have been confused with, among others, L. xylosteum). Clement & Foster (1994) cite a probable record from the British Isles.
Selected literature:
Clement E.J. & Foster M.C. (1994) Alien plants of the British Isles. BSBI, London: XVIII + 590 p.
Li D.Z. (2000) Lonicera. In: Cullen J. & al. (eds.), The European Garden Flora, vol. 6. Cambridge University Press, Cambridge: 436-452.
Yang Q., Landrein S., Osborne J. & Borosova R. (2011) Caprifoliaceae. In: Flora of China Editorial Committee (ed.), Flora of China, vol. 19. Science Press, Beijing & Missouri Botanical Garden Press, St. Louis: 616-641.