Why Invasive Species are an Issue For UK Gardeners



Many keen gardeners are well aware of the impact weeds can have on their gardening endeavours. However, many more might not be so familiar with the impact of Invasive Non-Native Species (INNS) or what the potential legal implications could be, in terms of both criminal and civil law – i.e. resulting in prosecution and/or getting sued.

The issues around INNS in gardens was recently highlighted by a Silver-Gilt award-winning stand at the RHS Chelsea Flower show this year. “The Enemy Within” was presented in the Innovation Zone where a range of INNS plants were grown. On one side of the stand a common setting of such plants was presented amongst broken concrete and fly tipped rubbish on an industrial wasteland, while on the other side the same plants were shown as attractive components of well-managed flower borders. This latter setting highlighted the source of most INNS, which were historically brought to the UK by explorers and botanists who noted their decorative value in their countries of origin. Hence,I think we now have numerous species from north America and Asia, for example, that have become rampantly out of control.

The principal reason for this is that these plants have evolved over millennia to be in balance with their native habitats. Bugs, diseases, fungi, herbivores and even the local climate have influenced the ecosystems so that these plants live harmoniously amongst the native flora and fauna. However, by taking them out of their home ranges and placing them in a completely new environment where none of these controlling agents and organisms exert control, the plants become aggressively invasive. This is the reason for most of our problems with INNS, both in gardens and in the wider countryside.

Ground elder is a perennial bane of many gardens, which was originally introduced to Britain by the Romans - it is therefore essentially naturalised here. It grows where it’s not wanted and spreads rapidly, particularly if disturbed by hoeing or other activities that fragment its root system, which creates hundreds of tiny new propagules. But it’s the more recent INNS that have the potential to cause much greater harm. Giant Hogweed has toxic sap that cause nasty blistering on exposed skin, and aquatic weeds like floating pennywort and New Zealand pygmy weed can destroy valuable and diverse pond habitat. There is a schedule of these plants, listed under the Wildlife and Countryside Act, which includes a number of species common to many gardens, including: rhododendron; cotoneaster; montbretia; Japanese rose; locust tree; and many others. If you are caught allowing these to spread into the wild, you could be found guilty of a criminal offence.

However, the real nasty is Japanese knotweed, which, due to its terrifying reputation, can have a blighting effect on property, significantly reducing its value. There have been a number of legal cases recently where homeowners have either been accused of caused knotweed problems for others or have been affected themselves by knotweed growing on adjacent land. The damage claims and settlements in these cases can be many thousands of pounds - often much greater than any fines incurred under infringement of the Wildlife andCountryside Act

It is therefore important that gardeners know what Japanese knotweed looks like. There is some useful Japanese knotweed identification guidance online. There’s also a lot of information about Japanese knotweed removal, should you be in the unfortunate position of finding it on, or directly adjacent to, your land.

With regards to other INNS, the advice of the PCA, as presented on their stand at Chelsea, is pertinent:

  • Know your weeds;
  • Think before you plant;
  • Manage wisely; and
  • Prevent their spread
Gardeners who follow this advice should be able to enjoy their hard work without fear of the nasty consequences that can arise from unscrupulous harbouring of INNS plants.

Comments