The award-winning scourge of mortgage applicationsJames Spice
It is difficult to think of a plant that has seen more of a reversal in popularity than Japanese knotweed. It arrived during Queen Victoria’s reign to plaudits and even awards. Broad heart shaped leaves and the delicate little white flowers soon made it popular with gardeners and horticulturalists, whilst its fast growing root structure and thick bamboo style stems earned the species a role shoring up the coal pits and railway embankments of Europe.
From this auspicious start Fallopia japonica has become a reviled plant, or weed. Today people are reticent to mention it, and when they do it evokes worry, sometimes fear. The benefits of this plant have long been forgotten, because it is an example of the introduction of a non-native species that is right up there with the Cane toad in terms of success. Both had a job to do in their early years, until it was realised that the detriment far outweighed the benefits.
The plant arrived to a 19th century Europe with an insatiable desire for the ‘new’, whether a food product, animal species or plant. The German Botanist, Phillipp von Siebold, found the species growing on the sides of volcanoes in Japan, then brought it back and sent them to horticultural societies around the world. From that introduction popularity grew, culminating in the award for the ‘most interesting new ornamental plant of the year’ by the Society of Agriculture and Horticulture at Utrecht, Holland.
Japanese knotweed has thrived in Europe and the US, territories where it no longer faces any of the natural predators prevalent in Asia. Siebold’s extraction site provides a dramatic example of this, the environment was quite hostile and regularly deposited ash would help keep the plant at bay. Faced with an absence of these hazards the plant has made quite a home for itself in a number of non-native territories. It was easy for it to lay down roots; they spread quickly and can be very destructive, yet the weed can lay dormant for over two decades.
The reason for the nervousness around Japanese knotweed is because it is now classified as an invasive species; in the United Kingdom it is the only plant that regularly that appears on mortgage applications forms. The weed easily establishes itself in new areas, and according to the ‘Wildlife Act, 1981’ landowners who allow the plant to spread to the wild are liable to legal action and fines.
Fallopia japonica has experienced quite a fall from grace since being one of the darlings of the horticultural world, however don’t spare it too much sympathy, you certainly don’t want this story becoming part of yours.