For those buying or selling a property, the experience can be exciting, stressful and sometimes tiring, particularly if faced with unexpected problems with plants and trees.
Nisha Vaidya, Mortgage Expert at Bankrate UK, said: “When buying a property, it is difficult to foresee problems such as Japanese knotweed. First time buyers in particular may be unaware of these issues, and could face disappointment if their mortgage provider is cautious to lend on a property which has problematic plants and trees.”
Working in collaboration with surveyor experts at Allcott Associates, Bankrate UK has created a guide to the five plant and tree species that sellers and buyers should be aware of when entering the housing market.
This includes how to identify the species, the potential damage to a home, how to remove the species with possible cost and laws associated with each.
*Readers who are concerned with plants or trees affecting their property should seek professional advice from their mortgage providers and licensed surveyors
Most mortgage providers are likely to refuse lending on a property that is found to have Japanese knotweed.
Famously, Japanese knotweed will deter buyers, making a property difficult to sell and can also cost thousands to remove.
Kim Allcott, of Allcott Associates, says: “Japanese knotweed can leave homeowners at risk of devaluation and also puts surveyors at risk of costly claims.”
She also comments: “Japanese knotweed has been known to cause structural damage to almost any part of a building it can reach, from tarmac drives to drainage pipes and foundations.”
Broker, Mojo Mortgages, agree: “Japanese knotweed is a nightmare. Most lenders decline on the spot as the risk is too high. Some mortgage providers will even decline an application if the weed is found on the neighbouring property.”
The weed can grow up to 10cm per day and is said to be capable of forcing its way through concrete which, in turn, can create large cracks in the brickwork and start to sink a property.
According to Knotweed Help, Japanese knotweed can devalue a property between 5-15% or in some severe, but rare, cases properties have been almost completely devalued.
The devaluation cost is usually equivalent to the cost of removing the plant and restoring the property to its original value.
This weed can be identified by its white flowers and bamboo-like stems which are famous for growing up to three meters in the summer when it grows quickest.
Its purple-speckled stems are also identifiers and make Japanese knotweed stand out amongst other plants.
According to Allcott Associates, evidence that the removal process has been started can be enough to convince some mortgage providers to lend, but this is an expensive and lengthy process which can take over three years and cost upwards of £10,000.
Some homeowners may wish to remove the weed themselves with chemicals and by burying it to a depth of five meters, but surveyors advise homeowners to instruct a treatment company that is a member of the Invasive Non-Native Specialists Association to begin the removal process.
A treatment certificate must be obtained once the removal is complete or the property is at risk of not being mortgageable in the future.
Nisha Vaidya says: “As Japanese knotweed is a big problem for those looking to sell their home, it is important for all homeowners to be aware of this species and act fast if they recognise it growing near their property.”
In the UK, it is illegal to plant Japanese knotweed or allow it to grow in the wild.
You are, however, under no legal obligation to declare the presence of Japanese knotweed on your property but you must not allow it to escape and spread into a neighbour’s garden.
If the weed causes damage to your neighbour's property you may be liable for a lawsuit if the weed can be sourced back to your garden.
Giant hogweed is a plant from the Apiaceae family which includes some well-known plants such as parsley, carrot, parsnip, cumin and coriander.
This weed is not native to the UK and was first introduced in the 19th century from the Caucasus Mountains and Central Asia.
It is now commonly found alongside riverbanks in the UK where its seeds are transported by the water.
“Giant hogweed, although stunning when fully grown, causes concern amongst surveyors because of its toxicity”, says our expert.
Chemicals in the sap can cause photosensitivity, where skin becomes extremely vulnerable to sunlight.
People who come into contact with giant hogweed often suffer severe symptoms such as skin blistering, burns, pigmentation and long-lasting scars.
If found on your property at the time of selling, you may find buyers will make a lower offer to reflect the cost of removal.
Giant hogweed looks like a large cow parsley and when fully grown it can reach towering heights of up to five meters with a width between one and two meters.
Their stems are green with purple spots and white hair and the leaves look like rhubarb leaf with their irregular, sharp edges.
The weed can also be identified in June and July when a cluster of small white flowers appear on umbrella-like heads.
Removal of giant hogweed is straightforward, but care needs to be taken to cover all exposed skin and dispose of plant debris carefully.
Giant hogweed is classed as a controlled waste and can only be disposed of in licensed landfill sites.
The site of the giant hogweed should also be closely monitored for several years after removal as there is a chance of regrowth.
There is no legal obligation for landowners to dispose of giant hogweed, but it is illegal to plant or grow this species yourself.
The Government website states: “You must not import, transport, keep, breed, sell, use or exchange, grow or cultivate, or release into the environment certain invasive alien species.
“If you do so, you can be fined or sent to prison for a maximum of up to two years.”
“Any trees near to walls can damage a neighbour’s or homeowner’s property if left uncontrolled, with willow, poplar and oak trees known to be particularly destructive.” says our expert
According to Allcott Associates, this is of concern in areas with clay soils, such as London, Milton Keynes, Colchester, Cambridge and other regions in the south-east of England.
This is because large root systems draw water from the ground, shrinking the soil that buildings stand on, which destabilises foundations and can lead to subsidence.
If oak, willow or poplar trees are growing close to your property this can cause subsidence which in turn causes structural damage.
Like Japanese knotweed, roots from these trees can break through concrete and drainage pipes and if root networks are extensive, they can also damage retaining walls and foundations.
How much these trees can devalue a home depends on the extent of subsidence damage. It is unlikely mortgage lenders will be happy to lend on a property with this type of problem.
There are several identifiers when looking to tell if you are working with an oak tree. For example, the leaves are often lobed, symmetrical, and growing acorns, while the bark is somewhat scaly. Oak trees are also known to have a thick trunk and can grow up to 21m in height.
Willow trees commonly grow near water and can be identified by their distinctive narrow leaves cascading down vines that are usually between 5-10cm long.
A common species of the poplar tree is the Lombardy poplar. They are known to reach heights of more than 30m, their leaves are diamond shaped and the branches grow almost vertically which gives it its identifiable shape.
“It’s difficult to put costs against these issues. If surveyors think there’s a risk that a tree could cause structural movement, we recommend soil and root analysis. These investigations are normally in the region of £1000 and need to be overseen by a structural engineer.”, says our expert.
Care must be taken when removing trees as sudden removals, or even cutting them back drastically, can result in the surrounding soil swelling, causing structural movement and damage.
If a tree on your property has a Tree Preservation Order (TPO) placed on it you will need permission from your local council to perform any works to the tree, be it removing a branch or felling the tree.
If the tree does not have a TPO, and is in your garden, you do not require permission to fell the tree.
Ivy is native across most of Europe and is often grown for decorative purposes as well as its berries acting as a good source of winter food for many birds.
It is a self-clinging climber that can grow quickly into the canopy of a tree and is also known to not only cause damage to trees but also to buildings.
“Ivy isn't a big problem unless it has grown the side of a house into the loft space. If this is the case, the lender could potentially decline the mortgage application, or hold a retention until it is sorted”, says Mojo Mortgages.
English ivy can be damaging to properties with its ability to cling to masonry and mortar, penetrating cracks or joints and shifting both roof tiles and guttering.
Kim Allcott says, “Removal is straightforward, but the costs of repairing masonry and re-pointing are often around £500 or more if the damage is extensive.”
Alongside these problems, all forms of climbing plants can be used by small wildlife like spiders and rodents, enabling access into a home.
While English ivy can look similar to Virginia Creepers from a distance, this weed can be identified by the dark berries growing alongside it.
English ivy is also usually green or light grey with heart-shaped, waxy leaves, whereas Boston ivy can be green, red and sometimes even purple.
While ivy can be removed from your building by hand, it is important to remember to kill the roots in your brickwork and the ground. A simple weed killing spray should work.
When undertaking removal of ivy from your home, you must ensure there are no birds nesting beforehand.
Under the Wildlife and Countryside Act 1981 it is an offence to damage or destroy the nest of any wild bird while it’s in use or being built.
Despite being seen as an attractive plant thanks to its colourful flowers and a good nectar source for bees, Himalayan balsam is said to be one of the most problematic weeds in the UK.
It is a non-native species that originates in the Western Himalayas before being brought to the UK in 1839.
One Himalayan balsam plant is said to be able to spread 2,500 seeds alone, so it is no surprise that it has spread so successfully and is now common all over the UK.
Despite their attractive look, surveyors advise homeowners to remove this weed due to its ability to smother native plants.
Himalayan balsam is a problematic plant for the garden.
This weed competes with plants, native to the UK, for light, nutrients, pollinators and space. In doing so it excludes other plants and reduces biodiversity.
As such, surveyors will also look out for this weed when carrying out their inspections and will advise homeowners to remove it.
Himalayan Balsam looks like Japanese knotweed and grows very aggressively.
This weed can be identified by its reddish coloured stems, dark green leaves with jagged edges, large brightly coloured flowers in variable shades of purple and pink. It also grows up to two meters in height.
“Fortunately, it’s much easier to remove Himalayan balsam than it is Japanese knotweed. This weed can be removed by cutting it below the lowest node or shoot on the stalk and pulling up the plant as it grows”, says Kim Allcott.
“The seeds can survive for as long as two years, so complete removal requires persistence and continuous vigilance.”
Allowing Himalayan balsam to spread onto adjacent land could result in your neighbour taking legal action against you.
Homeowners are not allowed to encourage the spread of Himalayan balsam and this includes moving contaminated soil or incorrectly handling and transporting contaminated material and cuttings.
Although overgrowth is not as costly or damaging to a home as the likes of Ivy and Japanese knotweed, overgrowth can prevent a thorough surveyor inspection.
Buyers should be aware of this when viewing properties as they may be at risk of inheriting a house with defects that a surveyor is unable to see.
Analysis of google search data in the UK between 2017 - 2020 found Japanese knotweed as the most popular query for homeowners with over 13,000 searches made for this species.
The next most searched query is for overgrowth with 10,820 searches made over the last three years. Despite this problem being particularly harmless when it comes to selling or buying a property, the UK is clearly coming unstuck when it comes to an unruly garden.
If you're looking to buy a property, you may want to research the costs of buying a home to learn about possible upfront costs and post-completion costs.