History of Japanese Knotweed in Europe

Originally described as Reynoutria japonica by Houttuyn in 1777 from Japan, that name was lost to botanists for over 150 years, in the mean time the same species was independently named Polygonum cuspidatum by Siebold and Zuccarini in 1845. It was not until the 1901 that Makino, a Japanese botanist, realised that the Reynoutria japonica of Houttuyn and the Polygonum cuspidatum of  Siebold and Zuccarini were the same Japanese Knotweed was introduced from Japan to the unsuspecting West by the horticultural activities of Philippe von Siebold via his nursery at Leiden (Holland) in the 1840s. It arrived at the Royal Botanical Gardens Kew in August 1850 in an unsolicited parcel of plants from the nursery of von Siebold of Leiden.  By 1854, the plant, under the pseudonym Polygonum sieboldii had arrived at the Royal Botanic Gardens in Edinburgh.  The plants were then sold by a large number of commercial nursery gardens around the country (Bailey & Conolly 2000), the sharing of cuttings and the discarding of unwanted rhizomes established the primary pattern of distribution.  Further vegetative spread followed naturally along watercourses, and artificially where soil containing rhizomes was moved above in road building and construction schemes.

Incidentally, after the publicity surrounding Siebold's description of Japanese Knotweed, it was discovered that there had in fact been an earlier introduction of the plant to London in 1825  The Horticultural Society had apparently been growing a Chinese accession of the plant in an artificial swamp in their garden in Chiswick, where it never flowered; under the impression that it was in fact Houttuynia! Although I initially thought they should have known better, I was similarly deceived on a visit to Japan, when I collected some young vegetative shoots of Houttuynia thinking them to be Japanese Knotweed!  

This is the first ever illustration of F. japonica in the West - Houttuyn 1777
All this information and more is in 'Prize-Winners to Pariahs - a History of Japanese Knotweed s.l. (Polygonaceae) in the British Isles'.  (Bailey, J.P. & Conolly, A.P.)

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