In the United Kingdom, there are over 200 known invasive plants and 36 of these are listed as species of special concern including some well-known names; Giant hogweed, Azolla, and Curly waterweed. But controlling all invasive plants is paramount – from the infamous knotweed to the not so famous Goat’s rue, to water weeds such as the smelly alien American skunk cabbage to the common weed Himalayan balsam, it is essential to prevent them from causing harm to our native ecosystems and the general economy. Invasive species really are an all-year-round enemy, and with some effectively disappearing from sight during the winter months – just how are invasive plants controlled in the UK?
In this article we cover:
- What does infestation look like?
- Should you control or eradicate?
- Why managing invasive species is so important
- The perils of DIY
- Should the public play their part in control?
Each species has its own growth pattern and cycle. For this reason, choosing the right method is vital to get the best result. Methods can vary in efficacy timings, some (such as excavation) are quicker than other longer-term solutions (such as biological control). In this article we outline some of the methods used to stop the spread of alien species and why it is vital to keep the momentum going. But first let’s take a look at what happens if invasive plants are not controlled.
Due to their aggressive growth pattern and high resilience to different climates, invasive plants such as Parrot’s feather can quickly dominate leaving native plants struggling for survival. Plants such as Japanese knotweed and Bamboo can also cause damage to structures as they look for weak areas to push through, breaking up hard surfaces such as concrete and brick.
What does infestation look like?
But lets start with seeing what infestation looks like. Below are just a few examples of infestations and damage, creating issues that cost UK businesses £thousands every year.
Control or eradication?
Some of the most common methods used for managing invasive plants include:
- Preventive Measures and Legislation: There are certain regulations and Acts in the UK that prohibit the import, sale, and cultivation of certain invasive plant species. The Wildlife and Countryside Act 1981 lists all banned species, and the EU Regulation on Invasive Alien Species also applies in the UK.
- Early detection: Invasive plants spread extremely quickly so the earlier they can be treated or removed the better it is for all involved and the environment. So, by far the best preventative is to have land and property regularly surveyed by professionals who can identify growth or regrowth (from a previous season) of invasive plants.
- Herbicides: Chemical herbicides are commonly used to control invasive plants, and, used selectively or as part of an integrated weed management strategy they can be a good long-term option. Applied professionally either by controlled spraying, stem injecting or leaf wiping, the herbicide targets the plant without harming surrounding native plants. Careful application will minimise environmental impact.
- Mechanical Control: This involves physically removing the invasive plants by either cutting, pulling up, or excavating the plant and ground they’re growing in (to avoid leaving any root system). Mechanical control is especially effective for rhizomatous species as it removes all parts of the plant to prevent regrowth.
- Biological Control: Introducing natural enemies (such as insects or pathogens) that specifically target invasive plants can help reduce colonisation. However, this method is not a quick fix as it relies on the plant’s natural predator to ingest it. This method is used with great success on Ragwort. Whilst a longer-term solution the Cinnabar moth caterpillars (Tyria jacobaeae) will happily feed on it all summer.
- Integrated Weed Management (IWM): Often a combination of methods is better than using just one, but herbicide is usually part of the mix because chemical control is required to deplete the plant’s growth system. Often a methodology will start with a mechanical method such as hand-pulling, then herbicide application to prevent grow back.
- Complete eradication: To get rid of an invasive infestation or colony excavation (where suitable) is the best option. Done properly all parts of the plant and surrounding soils will be excavated and removed from site – or in some instances buried in a suitable location on site. Certain regulations must be adhered to when removing and disposing of noxious weeds such as knotweed, and contractors doing so must hold a Waste Carrier’s license and take the waste materials to a landfill also licensed to receive it. To dispose of it in any other way (in the wild, in compost or green waste bins, to burn or smother it as some examples) is illegal.
Why managing invasive species is so important
Managing invasive plants is crucial on so many different levels, and for so many people, organisations and business sectors. Not just to protect our native biodiversity and ecosystems but to reduce the economic and social impact.
Agriculture, forestry, horticulture, leisure and tourism industries can all be affected by invasive species as they deplete our native plants, trees and crops and impede use of waterways. Local Authorities are also required to control invasive plants (as well as general amenity weeds) not just as part of their grounds maintenance targets but to keep the public safe from toxic plants such as Giant hogweed or Hemlock. Some plants such as Ragwort are toxic to livestock and horses, making it essential for equestrian centres to keep a watch for suspicious looking plants on their land.
If invasive plants are not controlled or removed they can cause significant ecological impact – altered Ph levels in soils, depleted oxygen quality or light availability will lead to a changed ecosystem. In some environments this can lead to increased fire risk, blocked hydrology systems and contaminated water.
Public involvement
The general public can play their part in assisting specialist contractors to control and eradicate harmful species. Alerting them to a sighting of Giant hogweed along a riverbank can save potential harm being done from accidental contact to passers-by and pets. It’s vital that the public are vigilant when out and about not only for their own safety but for the safety of their pets, and for others walking the same route. It’s easy to send pictures of suspected weeds to us if you’re not sure what it is.
How to get rid of invasive plants
The perils of DIY
Whilst there are lots of articles on DIY methods, there is also evidence that most do not work long term – or certainly very little evidence to prove their efficacy long-term and for some species disposal of plant material and waste soils is governed by legislation which requires special licenses, equipment and training. The real issue with DIY methods is the lack of knowledge and expertise and the high expectation that comes from seeing initial results of weed eradication – only to find it comes back even stronger in the following season. Because if not done properly, weed control is not done at all!
As the issues caused by colonisations pose serious threats as touched upon in this article, it’s clear that without effective measures in place invasive plants will continue to thrive. Professional identification, treatment and eradication methods must be deployed long-term so that we can protect the UK’s habitats.
Our specialist control services are geared to help individuals and businesses alike. With highly experienced teams working across England, Scotland and Wales, our challenge to contain or remove invasive plants is constant. To see how we can help you get in touch.