Japanese Knotweed Solutions Ltd. Blog "Growing Concerns"

It’s been having SEX!

April 24th 2015

Having been faithful to its self for years (ie reproducing asexually through fragments and propagules) Japanese Knotweed has been out on the town and fooling around without any form of protection – resulting in... fertile seeds!

CABI (www.cabi.org) hypothesised that climate change and global warming could result in plant species shifting their distribution northward? They expected that phenological changes could be the first signs of populations located near their distribution limit – (meaning that the earlier flowering of a species would indicate its adaptation to the climate and its ability to then progress Northwards).

Testing has been carried out by CABI in Canada of Japanese Knotweed (Fallopia japonica) and its hybrid Bohemian knotweed (F x bohemica) of the theory that climate warming could allow the production of viable seeds in the most northerly of its populations. Seeds were collected along a 550km transect in Quebec and tested for germination.

The results showed that Japanese Knotweed has a large number of seeds with a very high germination rate (93%).

The geographical limit for viable seed production in North America has thus been extended to Quebec City some 500km North of the formerly reported limit! The Bohemican Knotweeds are genetically diverse whereas the true Japanese Knotweeds all share the same genotype – this suggests that the Bohemian knotweeds mostly arose from seed while the ‘true’ knotweeds result only from propagation of rhizome or stem fragments.

The conclusion was that the effects of climate change are already palpable on the phenology of invasive plant species at their Northern distribution limit. Bohemian knotweed – which was until recently rare in Quebec, could rapidly spread in the near future with the help of viable seeds being regularly produced.

With the impact of invasive species now being recognised more in the UK one is left wondering whether the next major change will be the production of viable seed within the UK populations of Fallopia bohemica?

This would be a major game changer within the management and control industry and require a complete overhaul of standard eradication techniques and warranty packages.

Mike C

with thanks to CABI