JAPANESE Knotweed may not be the only invasive plant your home is at risk of.
A weed expert has issued an urgent warning over another unwanted shrub which can knock value off your house.
The plant is viewed by the Department for the Environment, Food and Rural Affairs (Defra) as an invasive non-native species.
It has previously caused problems for British railways.
Buddleia davidii, also known as butterfly bush, has been planted widely in wildlife-friendly gardens after being introduced from China.
It is highly regarded by some for it’s ability to attract insects.
However, according to Jonathan Barton, director of PBA Solutions, Buddleia can be “more troublesome” than Japanese Knotweed.
He explained that the plant’s “ability to spread by seed” is the what makes it more harmful.
“Those seeds [are] able to germinate in tricky places under pretty inhospitable conditions,” Barton revealed.
“This ability to germinate easily is why buddleia is often seen growing out the sides of buildings and other built structures.
“Nine times out of 10, if you look up at a building and see a plant growing from the brickwork or chimney stack, it is buddleia.”
The expert added that the plant seeds can be detrimental once they have embedded in brickwork.
“Once established in a building wall or roof, the plant sends down, fibrous roots and can cause significant damage to buildings as it grows,” he said.
It has been estimated that a single buddleia flower spike can produce over 40,000 seeds.
In contrast, Japanese Knotweed most commonly spreads through direct rhizome growth, a type of stem-like root that can extend several metres across land.
Just a small fragment of this can be used by the plant to reproduce elsewhere.
Barton described how harmful the characteristic purple flower can be to buildings.
One simple way to prevent buddleia from spreading is to cut off the flowers before they set seed.
Ideally, dry the cuttings out quickly and compost them in a sealed bag.
Of course, if you have a large buddleia then this could be difficult or even impossible to achieve.
Buddleia can be pruned back every year and this will limit the size of the plant and the number of flowers.
“Buddleia’s ability to reproduce and quickly cause damage in inconvenient locations make it a problem that should be in the spotlight more,” he explained.
“Demand for buddleia removal is growing year on year, with more property managers seeking our expertise than ever before.
“We have seen buildings ripped apart due to buddleia, and railway arches frequently become the victims of buddleia.
“The need for immediate eradication by many people will result in extensive demolition and re-building of walls and roofs damaged by the plant.”
Barton revealed how to remove the pesky weed, which can be difficult to tackle.
“Herbicide applications are the obvious choice, but don’t work as well on older plants,” he said.
“[They] are only likely to be completely effective if a structured treatment regime is completed over several years.
“However, a refurbishment developer will want buddleia completely eradicated within a short period.
“As a result, walls and other building structures are often completely ripped down when refurbishing a property which means that buddleia can be very damaging.
“Similarly, Network Rail reportedly finds Buddleia to be one of the most prolific problem weeds out-competing other species and damaging ecosystems.”
“Buddleia has been planted in recent years due to being attractive to insects and is often recommended to encourage wildlife into gardens,” said Mike Clough, CEO at Japanese Knotweed Solutions Ltd.
“This may lead to damage to buildings in the future if home owners have planted too close to structures.
“Buddleia can be very damaging to buildings and hard surfaces – Network Rail class the two species as being very similar in terms of damage caused.”
