Selling a property with Japanese Knotweed in the garden?

new Japanese Knotweed sprouting near Sevenoaks
new Japanese Knotweed sprouting near Sevenoaks
Snapped Japanese Knotweed Sevenoaks
Snapped Japanese Knotweed Sevenoaks

Late April to early May you may notice Japanese Knotweed stems starting to sprout up amongst ‘dead’ patches along the ground.  It may look innocent and bamboo-like in appearance – however,  similar to bamboo, it grows up and by next month you will notice it dwarfing all the other (if any!) plants in the area. This means that it blocks out their sunlight and continues to grow inhibited.

One real concern over the plant is its speed at growing and re-growing. Snapping the stem up does give a satisfying popping sound, however it is really important that the stem left in your hand is not just thrown away as that has the potential to grow into another plant.


Currently in the UK, that is exactly the way that the plant has spread!  The plant can grow over 10cm a week and there is nothing ‘natural’ that will kill it or slow it down. The rhizome system (roots) may extend to, and beyond, a depth of at least 2m and extend 7m laterally from a parent plant.

So what has that got to do with selling a property?!

Due to the speed of growth and its ability to regrow into another plant, mortgage lenders are becoming increasingly concerned about lending money for properties which have Japanese Knotweed present in the garden.  The plant is not harmful to people’s health (I’ve heard the dead stems are great pea shooters!), but if left ignored the plant can and naturally will ‘migrate’, including to the base of the property, and root itself into the foundations of the property. This is where it can be a real problem.  The speed in which it grows means that if knotweed is found in or near a property (as in many cases in London), mortgage companies may be concerned, or in some cases refuse to lend money unless a management plan is in place.


What is a management plan?

A management plan is where a company (such as Longfield Knotweed Solutions Ltd) provide a treatment plan for X amount of years. In other words, we will visit, inspect and treat as necessary over the next X number of years.

Why so long?!

Currently the main method of controlling Japanese Knotweed in most properties is through using chemicals (called pesticides, and used to be called herbicides).  An alternative is excavation to potentially a depth of 3 meters and 7 meters around the crown… for small patches of knotweed this is not cost effective!

  • Chemical treatment has varying degrees of success in year one.  If the infestation is small then it is generally killed in year one. However it does depend upon time year the treatment commences and how long the infestation has been present as well as other factors.
  • In year two all regrowth is treated as necessary.
  • Year three any further regrowth is treated. For small infestations year three is simply to inspect and confirm eradication.
  • Year four and five is the repeat of year three, with a completion certificate and report detailing treatment, and findings over the time.

For selling a property, mortgage lenders often require 5 years. Longfield Knotweed Solutions Ltd will offer 3 – 5 year plans after speaking to the owners  (for example, for owners letting a property, 5 years may not be necessary as the property is not going to be sold in that time frame).

Longfield Knotweed Solutions Ltd does not like to offer one-off treatments in general, as often this does not kill the plant, rather it often sends it into dormancy, only to reappear next year.  One-off treatments do control the knotweed in that year, but long-term does little to control and eradicate the plant from the property/site.

The final product! Japanese Knotweed jam


Japanese Knotweed and Ginger Jam
Japanese Knotweed and Ginger Jam

It adds an earthy taste to the jam – a bit like rhubarb, and a good ginger kick at the end.

The best time to pick the ends of the knotweed is April–May, before it becomes too stringy and mature.

Next year, perhaps I’ll find enough knotweed to make more than 2 jars of it!

For anyone interested I found the recipe online ( It’s very straightforward!