Japanese knotweed grew on the hedge running along the boundary of my rear garden last summer. I sprayed it with some weed killer and it died back during the winter.
I’ve been keeping an eye out for it returning but I haven’t seen any sign of it yet. This is despite knotweed tending to regrow in March. Does it mean I’ve successful got rid of it?
Japanese knotweed is described by the Environment Agency as ‘indisputably the UKs most aggressive and destructive plant’
MailOnline’s Property expert Myra Butterworth replies: Japanese Knotweed can be a homeowners’ nightmare.
The plant can spread across land aggressively and destructively and is notoriously difficult to get rid of.
Some lenders refuse to offer mortgages on properties with the plant. This can make properties almost impossible to sell.
It means successful removal of the plant is essential if you hope to sell the property in the future.
The plant can die back over the winter after treatment and start to regrow when the weather improves, so it’s important to ensure it is professional treated to ensure it never returns. However, this can be costly, with proper treatment starting from £2,500 per tensquare metres.
Jonathan Harris, director of mortgage brokers Anderson Harris, says: ‘Japanese knotweed is a hardy, bamboo-like plant that has become increasingly common in recent years, especially in the countryside.
It can grow several metres into and above the ground, eats into buildings and tarmac, can block underground drains and ruin patios and paving. If left untreated, it can cause serious structural damage to a property and lenders are therefore cautious about lending on properties affected by it.
The main concern is that a property with knotweed may not be good security for a mortgage, due to the risk of damage posed by the plant and problems it might cause with reselling.
‘Historically, any evidence of knotweed would lead to a mortgage being declined outright. However, lenders are increasingly adopting a more pragmatic approach to knotweed as more specialist knowledge and treatment of cases becomes available. In short, it’s now possible to get a mortgage when knotweed is apparent.
‘Knotweed is hard to conceal and surveyors are trained to look for the signs, so a standard mortgage valuation is likely to reveal an infestation. Surveyors are now likely to classify the extent of the problem and categorise the level of threat. Often it will come down to the proximity of the knotweed to the property itself. For example, anything within seven metres of the property might be deemed unacceptable but if further away, might be acceptable.
Lenders may also be able to consider a case where a specialist assessment has been made and remedial work covered by an insurance-backed guarantee has been carried out and confirmed. Companies that treat knotweed will typically cover their work with a guarantee of up to 10 years.
‘It is important for borrowers to flag any known knotweed issue with their mortgage broker and lender and investigate whether treatment has been completed and what level of cover is attached. That will help to raise the issue upfront, which will help identify a potential lender.’
The recent cold weather may have delayed the start of the Japanese knotweed growing season by at least two to four weeks
Tom Payne, managing director of TPKnotweed, says: ‘There are lots of factors that you need to take into consideration when looking at whether or not Japanese knotweed will re-grow the following season.
‘There is no miracle cure for treating Japanese knotweed and with herbicide treatments, the key is to ensure that a structured five-year treatment programme is implemented consisting of repeat treatments at key times throughout the growing season. We normally recommend three years of herbicide treatments (two per season) followed by two years of monitoring to ensure all Japanese Knotweed has been effectively killed.
‘Japanese Knotweed contractors use specialist licensed herbicides that are stronger than ones that can be purchased from a local garden centre so eradication can be achieved quicker. Glyphosate-based domestic weed killers will still work, it will just take longer.
‘If treatment has only taken place for one or two years, then yes, it is highly likely you will experience re-growth. With such an extensive underground rhizome network it takes a long time for the herbicides to kill the whole plant.
‘Another option is to have the Knotweed excavated and disposed off site to a licensed landfill facility. This means that there are no restrictions on land use or development works and re-growth will not occur if excavated by an experienced specialist.
‘When you come to sell a property affected by Japanese Knotweed, there is a question on the Law Society TA6 Property Form that asks if the property is affected by Japanese knotweed.
‘If answered ‘Yes’, you need to see if there is an appropriate treatment programme in place from an accredited specialist with a 10-year insurance-backed guarantee upon completion. Without this in place the majority of UK lenders will refuse to grant a mortgage.
“It must be noted that while Japanese Knotweed is an aggressive and problematic plant, it can be treated and killed and should not hinder a property sale.
Nic Seal, managing director of Japanese knotweed removal specialist Environet UK, says: ‘I’m afraid it’s more likely that the Japanese knotweed hasn’t yet emerged because of the unseasonable cold snap we’ve experienced in February and March this year, which has delayed the start of the growing season by at least two to four weeks.
‘Unusually, we may not see the plant begin to awaken from its winter hibernation until the early April, when the ground temperature reaches around 4°C. Then red or purple asparagus-like shoots will emerge from the ground and quickly turn into green bamboo-like stems, growing at a rapid rate, up to 10cm per day, causing untold damage to property foundations, patios, driveways, cavity walls and drains.
‘Unfortunately over the counter weed killers are extremely unlikely to kill knotweed, as are other DIY methods such as burning. Homeowners should be aware that such attempts can then make professional treatment more difficult.
‘Professional firms will treat the knotweed, either with herbicide over two to three years, which is the least expensive option, or by excavating the plant from the ground which takes just a couple of days to complete. They should provide you with a five or 10-year insurance-backed guarantee for the work, which you will need if you ever come to sell the property.
‘You may have a claim against the landowner to the rear of your garden, if it can be proven that the knotweed has encroached from their land onto yours, so it would be wise to seek legal advice in this respect. While it isn’t illegal for Japanese knotweed to be growing there, it is illegal to allow it to spread onto neighbouring properties and if that is the case, they will be responsible for the cost of treatment.
‘Japanese knotweed has spread so rapidly across Britain in the last decade that it’s really no longer a case of winning the battle. Those who discover knotweed on their land should take immediate action and put a professional treatment plan in place to protect their property and protect themselves against litigation from their neighbours.’