[Yorkshire Evening Post 15 July 2010] -- Foreign weeds which can break through concrete and grow as tall as a house are changing the UK's Yorkshire landscape and could even stop you getting a mortgage, as Neil Hudson discovered. Some banks will refuse to give you a mortgage if it is found you have Japanese knotweed on your property. The weed was introduced by the Victorians as an ornamental plant but has since spread to most parts of the UK. It is one of a number of non-native, so-called 'invasive' plant species which have come to the UK's shores since the 18th century. Most of the non-native weeds are good at adapting to new environments and often outgrow plants native to the UK.
KNOTTY PROBLEM: Nick Hartley an expert on Japanese knotweed with some of the plants growing wild near his home at Methley, near Leeds.
Japanese knotweed can grow up to 3m tall and forms dense thickets but it is its underground root system which is the real problem. It can burrow up to 3m into the soil and extend a further 7m away from the plant in any direction. It is so strong that it has been known to break through concrete and therefore has the potential to damage foundations.
If you try to pull it up and so much as a piece the size of your finger tip remains, the plant can regrow.
It is just one of a number of foreign plants which are causing havoc in the Yorkshire and the UK as a whole.
A spokeswoman from Barclays Bank said: "Our policy is not to lend to anyone who is known to have Japanese knotweed on their land until they have in place a firm action plan to deal with it."
However, other banks are more lenient. A spokesman for Yorkshire Bank said: "We would base any lending decisions on the individual valuation. Clearly, there is a difference between someone with a small garden overrun by knotweed and someone with a three acre garden who has a bit at the bottom."
Lloyds also review mortgages on a case-by-case basis but crucially, all acknowledged they do consider the impact of Japanse knotweed.
Paul Evans, Natural England regional biodiversity coordinator for Yorkshire and the Humber, said: "There is a whole range of introduced plant and animal species in the UK, some which arrive naturally and others which are brought here by humans.
"Foreign plant and animal species have been brought into this country by man since Roman times. Then there were the Victorians, who went all round the world and brought back all kinds of plants.
"Climate change has also brought new species to our shores, as they have moved northwards following a warming of weather.
"Globalisation has seen a massive increase in the movement of plant and animal species. In 2005, it was estimated there were some 2,200 non-native plant and animal species living in the UK. Many are harmless and in fact could be considered as of value to our natural heritage, but some can have a significant impact. These 'invasive' species can have a significant impact on our environment and direct rapid action is needed to reduce detrimental effects"
In March, the government approved plans for the release into the wild of the sap-sucking psyllid bug, an aphid-like creature which preys on Japanese knotweed but it's long-term impact remains unclear.
It is hoped the introduction will not mirror the story of the cane toad, introduced into Australia in the 1930s in a bid to combat the cane beetle, which was devastating sugar crops. Some 3,000 toads were introduced but the toad didn't do what it was supposed to it ignored cane beetles and instead prayed on other insects. There are now some 200 million cane toads in Australia and it is considered a pest.
The psyllid bug has been released at three secret sites and its progress will be monitored over the coming months. If all goes well, it will be released at a further 10 sites and if there are no negative effects, it will be released into the wild across the UK.
But even that will not mean the end of the dreaded knotweed. The best gardeners and unsuspecting householders can hope for is that the prolific plant becomes less of a menace and that the psyllid does not take a liking to anything else in the meantime. As for the other 2,199 invasive species, the battle looks set to continue for some time.
Ashley Joy, from Leeds-based Ashtrees Ltd, which specialises in the treatment of problem plants, including Japanese knotweed, said: "It is a growing side of our business, at the moment we are treating 22 sites in West Yorkshire, some for councils and private companies, others for individuals.
"Problem weeds, such as Japanse knotweed and giant hogwort, have always been a problem but I think people are now starting to wake up to the fact.
"The point to make is that there is hope for people who discover they have things like knotweed, it can be treated."
