Japanese knotweed Portsmouth hotspots revealed in interactive map by Horticulture

It’s believed that Japanese knotweed was originally imported into the UK from Japan back in the nineteenth century, when engineers thought it would stabilise and beautify railway embankments.

In winter the plant dies back to ground level but by early summer the bamboo-like stems emerge from rhizomes deep underground to shoot to over 2.1m.

According to data from gardening magazine Horticulture, more than a dozen places in the city are recorded as having been struck by the weed. Areas affected include Fratton - which has the most recorded cases - Southsea, and Copnor.

The problem is that the plant has been known to cause damage to building structures by targeting weak points and attempting to grow through them.  It’s not illegal to have Japanese knotweed in your garden, but on your property, you should aim to control the plant to prevent it from becoming a problem in your neighbourhood.

Japanese knotweed is typically spread accidentally through the movement of soil or gardening waste, or via rivers and streams when pieces of rhizome break off and take hold in new locations.

You can find out where Japanese knotweed has been spotted in your area by using Horticulture's interactive map here.