While Japanese Knotweed 1usually grabs the headlines, there are plenty of other invasive species you ought to be aware of as we all have a duty to avoid spreading them into the wild or agricultural land where they can propagate at an alarming rate.

 According to Government advice2 gathered from Natural England, the Environment Agency and the Dept for Food and Rural Affairs (DeFRA) we must all have a duty to:

  • prevent harmful weeds on our land from spreading on to a neighbour’s property
  • prevent invasive non-native plants on our land from spreading into the wild and causing a nuisance.

 Harmful weeds

A number of weeds have been identified as a danger to animals, or likely to cause problems for agricultural production if left to spread unchecked. While it’s not an offence to have these weeds growing on your land, you must prevent them from spreading to agricultural land, particularly grazing areas or land used to produce forage, like silage and hay.

The danger species include common ragwort, spear thistle, creeping or field thistle, broad-leaved dock and curled dock. Here’s a handy guide to identifying the danger species3.

 Invasive species

Preventing the spread of invasive, non-native plants is a far more serious matter, with offences under the Wildlife and Countryside Act 19814 carrying the risk of heavy fines and imprisonment5. Control measures that you must have in place include restrictions on the disposal of contaminated soil and cuttings.

The most commonly found invasive, non-native plants include:

  • Japanese knotweed (Fallopia japonica)
  • Himalayan balsam (Impatiens glandulifera)
  • Rhododendron (Rhododendron ponticum)
  • Giant hogweed (Heracleum mantegazzianum)

The first three are a threat to native flora and habitats, as they are aggressive and form dense stands that exclude other plants. Giant hogweed is less aggressive to other plants, but is poisonous and can cause severe skin reactions.

While you do not have to control or remove these plants from your own land, you must not allow them to spread to neighbouring properties. It is illegal to plant them in the wild!

Find out how to identify these and other invasive non-native plants6.

While the chances of the grounds of a block of flats being affected by these issues may seem low, it’s probably a good thing to check. Remember, invasive species were often only introduced because they were attractive to gardeners so some well-meaning soul may have planted them in good faith!

One of the worst offenders at the moment is Himalayan balsam (Impatiens glandulifera), a relative of the innocuous Busy Lizzie that reaches well overhead height. Deceptively pretty, it’s becoming a major threat, ousting native species on riverbanks and wasteland, but it can also invade gardens.

Originally introduced as an ornamental garden plant, it is now smothering and threatening other native species, especially on riverbanks and wasteland when left to run riot.

If you have it in your grounds, you do not actually have to remove it, but you should take steps to control it and to prevent it from spreading. So do look out for its pink flowers from June to October and stop it in its tracks if you can.

You or your gardeners should consider non-chemical means of control, pulling or cutting the plants before they flower and set seed.  Just grab the stem as low down as possible and give it a gentle but forceful tug.

It comes out of the ground easily and brings the full root up with it. Snap the root just above the lowest nobble to prevent re-rooting and can just leave it on the ground to rot down. Balsam tends to grow near nettles, so do wear gloves if you try this.

There’s good advice on this and all approaches to Himalayan balsam control7 at the Royal Horticultural Society web site.

A year of pandemic lock downs has taught us the value of private gardens and open countryside alike. We all have a role to play in protecting it.

  1. https://deacon.co.uk/2019/03/22/japanese-knotweed-still-an-issue/
  2. https://www.gov.uk/guidance/prevent-the-spread-of-harmful-invasive-and-non-native-plants
  3. https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/69265/pb4192-injurious-weeds.pdf
  4. http://www.nonnativespecies.org/index.cfm?pageid=67
  5. https://www.gov.uk/guidance/prevent-the-spread-of-harmful-invasive-and-non-native-plants#enforcement
  6. http://www.nonnativespecies.org/index.cfm?sectionid=47
  7. https://www.rhs.org.uk/advice/profile?pid=480


The opinions and views expressed in the above articles are those of the author only and are for guidance purposes only. The authors disclaim any liability for reliance upon those opinions and would encourage readers to rely upon more than one source before making a decision based on the information.