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  • Joe Bleasdale

Invasive Weeds and Plants: How To Identify And Dispose Of Them Safely

If you own a garden, or there are plants growing on or in your property, you may, at some point, come across an invasive species. Although some may seem like a desirable addition at first, Prince Krofa & Sons knows that these weeds can turn into more than just an eyesore, in some cases, causing structural damage to homes, affecting its value, as well as harming surrounding wildlife and habitats.

This article will help you to identify some of what the government defines as “injurious weeds” and “invasive plants”, and how to deal with them.

What is an invasive species?

Although “invasive species” can bring to mind John Wyndham’s sci-fi novel The Day of the Triffids, it has nothing to do with plants on an out-of-control murdering rampage.

Species of animals and plants have been transported worldwide for generations by human activity, and while “non-native species” can thrive in new areas and pose no threat to others, “invasive species” will often have a negative impact if they come into contact with other organisms and environments.

According to the Natural History Museum, invasive species are a bigger biological and economic threat than climate change.

How are invasive species regulated?

A full list of non-native species of animals and plants that cannot be allowed to escape into the wild is detailed in both the Weeds Act 1959, and the Wildlife and Countryside Act 1981, which has been amended several times, most recently by the Invasive Alien Species (Enforcement and Permitting) Order 2019, to accommodate new discoveries.

The aim of this act is to prevent invasive non-native plants on your land from spreading into the wild and causing a nuisance, and to prevent harmful weeds on your land from spreading onto a neighbour’s property.

As of today, a fine of up to £5000 or up to 2 years’ imprisonment are the maximum penalties for knowingly allowing contaminated soil or plant material to spread into the wild.

“Injurious weeds”

The Weeds Act 1959 lists five types of weed as being “injurious”, which, in this context, means that, while they are not poisonous or immediately harmful to humans or livestock, they can cause great harm to agricultural land, particularly grazing and conservation areas. Therefore, the property owner is in charge of controlling them.

The five “injurious weeds”, in order from most- to least-widespread, are:

1) Common ragwort (Senecio jacobae) – this is toxic.

2) Spear thistle (Cirsium vulgare) – this produces seeds which can easily be blown across property and field boundaries.

3) Creeping / field thistle (Cirsium arvense) – this can dominate grassland vegetation by spreading large systems of underground roots.

4) Broad-leaved dock (Rumex obtusifolius) – this thrives in areas with high nitrogen levels.

5) Curled dock (Rumex crispus) – this is mostly found on arable and waste land.

Most of these weeds can be dealt with by cutting at the roots or digging up. Composting is not recommended as many can survive the process and spread further, and while persistent use of herbicides can be effective, you must check that you are in an area of special conservational interest, and if there could be a risk of damaging rare or valuable flora and fauna.

In any situation, it is better to seek expert advice.

“Invasive plants”

The Wildlife and Countryside Act 1981 lists invasive plant species that are already causing problems in the UK in Schedule 9, with an amendment in 2010 adding another 34 newly-discovered invasive species.

The listed plants are so damaging to the environment, it is a criminal offence to sell, plant or allow them to grow in the UK, and are punishable by the aforementioned penalties.

The five worst offenders are:

1) Japanese knotweed (Fallopia japonica)

- Originally brought to the UK as an ornamental plant in the Victorian period, Japanese knotweed is estimated to cost the UK economy £166 million every year, according to a 2019 Parliamentary report [link]. It can devalue properties by up to 20% if left unchecked.

- Its root system is strong and fast-growing, to the point where even leaving the smallest morsel of root after cutting can cause knotweed to grow back.

- Removal methods include spraying with chemicals, covering and burying at a depth of 5m minimum, burning the roots or, depending on the location and value of the property, an excavation.

2) Giant hogweed (Heracleum mantegazzianum)

- Hogweed is transferred by its seeds, which are carried by birds and insects, and along waterways.

- It is not as difficult to control as Japanese knotweed, but it can take up to 10 years to eradicate completely.

- It is “phototoxic”, meaning the sap contains toxic chemicals that cause blistering on human skin in bright environments (a friend of the author actually had first-hand experience of this: she saw a weed in her garden she didn’t recognise, and, without protection, uprooted it, when, after about an hour, her skin started to blister, and she ended up with third-degree burns). Therefore, removing hogweed without specialist advice and equipment is difficult.

3) Himalayan balsam (Impatiens glandulifera)

- This is especially found on riverbanks and waste lands, and can present a big problem for river bank erosion.

- It can grow to up to 10 feet (~3m).

- Its pretty pink flowers means it can be deceiving, and is is often spread by people passing on seeds to friends to use in their gardens.

4) Rhododendron ponticum

- Rhodedendron was first used in the UK as a decorative garden plant in about 1763.

- Its millions of tiny seeds are spread rapidly by the wind, meaning there are few parts of the country not affected by rhododendron today.

- It is very difficult to remove with pesticides or by digging up.

- It is toxic to some animals, and causes damage to woodlands, meadows, heaths and floor canopies.

5) New Zealand Pygmyweed (Crassula Helmsii)

- This is one of five water-based plants banned from sale in the UK.

- It is most commonly found in the South East and North West of England.

- It creates a dense matting on the surface of ponds, making them virtually uninhabitable to fish and frogs, and can confuse wet land for dry land, making it dangerous to children and pets.

Removing these invasive plants can be hugely expensive and time-consuming, and may require contacting the Environment Agency and a specialist surveyor before the job is carried out.

Various links in this article give in-depth advice on the removal of certain invasive species.

What about climbing plants?

Although not covered in either the Weeds or Wildlife and Countryside Act, climbing plants, the most common in the UK being ivy, can have as much of a detrimental effect on the value of a property.

You may like the look of ivy growing up the side of buildings, like this poison ivy on a Victorian terrace, but the invasive roots can cause considerable damage to property surfaces.

Moisture from invasive creeping plants can particularly impact old brick homes, wooden walls and fences, timbers, siding, painted surfaces and weakened or unsound structures. Prince Krofa & Sons recommends limiting ivy to solid masonry walls with no cracks, keeping it contained, and if it gets out of control, as in this example, cutting it off at the roots so the plant dries out further up.

RHS Gardening has a comprehensive list of climbing plants that are not invasive and do not harm property value, such as jasmine, wisteria and honeysuckle.

UPDATE, June 2022: Most pesticides can pose a risk to humans and animals. For this reason, Consumer Notice have published a guide to organic, homemade, and agricultural alternatives.

If you live in London or the Home Counties and are having problems with invasive plant species, PKS, whilst working with specialists teams, can advise on the best course of action.

To contact us, or to book a survey, visit us here.

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