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Japanese Knotweed: Risks, Cures & Costs

If you read the popular press at the moment it seems that there is an alien invader running amok in the property market - an invader so determined that it has the capability to take over your property, render it unsaleable and even, potentially, reduce it to a pile of rubble!
I'm talking, of course, about Japanese Knotweed. It is a problem which has received much coverage of late due to the apparent refusal of many lenders to grant mortgages on affected property. So in this report I'm going to look at the issue; attempt to separate fact from urban myth, look at the risks (and possible opportunities) of buying an affected property, particularly at auction, and find out what can be done about it.

First of all a little background, to help us understand the extent of the problem: Japanese Knotweed (Fallopia Japonica) was brought to Britain from East Asia by the Victorians as an ornamental plant. Since then it has 'escaped' into the wild and spread profusely due to its voracious appetite for growth and lack of natural predators - insects and fungi keep it in check in Asia.

So how to spot it on any property you may be thinking of buying? The mature plant has arching, hollow bamboo-like stems covered in purple speckles which can reach 2-3m high. The 'ace of spades' shaped leaves grow from these stems in a zig-zag pattern, and are up to 120mm long. Lace-like white flowers appear not in the spring but in the late summer and early autumn. The plant dies back to dry canes in winter and (being a perennial) new growth appears in the spring.

It's most distinguishing factor is, perhaps, its appetite for growth - which also complicates removal. In the UK Knotweed spreads through its rhizome or underground stem system rather its seeds (which are unable to develop here). The rhizomes can extend 7m from the centre of the plant, and occasionally as much as 3m deep, and grow up to a metre in a month. According to some reports a new plant can grow from a 10mm section of cut rhizome. The rhizomes can also remain dormant in the soil for 20 years or more.

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