Five of the UK’s most invasive garden plants – and how to remove them

Do you have any dangerous plants lurking in your garden? Discover five of the most invasive species in the UK, and how to handle and remove them.

Did you know that seemingly harmless plants could spell disaster for your beloved garden and pose a serious risk to you, your animals and even the value of your home?

With an astonishing 109k searches in just the past month, the phrase ‘invasive species’ underscores the urgent need to remove these unwelcome and dangerous plants from our gardens.

They take over gardens fast, spreading seeds extremely quickly, as well as suffocating other plants and harming wildlife. Some can even be dangerous to pets and people, as well as up to 25% of your house value.

The experts from London rubbish removal company, Rainbow Rubbish Removals, are here to help by listing the five most invasive plant species that need immediate removal from your garden and providing guidance on identifying and removing them.

1) Giant Hogweed (Heracleum mantegazzianum)

Giant hogweed, the most dangerous invasive species in the UK, can grow taller than 10 feet. While it may look pretty, it’s advised to remove the plant as soon as you see it, as this plant poses a significant risk to individuals unaware of its harmful effects.

The negative/dangerous traits of giant hogweed:

  • Exposure to the sap can result in skin burns
  • Contact with the plant can induce rashes and blisters on human skin
  • There is a risk of potential blindness if the plant comes into contact with the eyes
  • It exhibits invasive behaviour, spreading rapidly

How to remove giant hogweed from your garden

To control giant hogweed in your garden, focus on preventing seed formation to stop its spread. Removing the plant entirely is the most effective method. Always wear protective gear when handling the plant, and cut it just below the growing point underground. If needed, apply herbicide at the start of the growing season in May.

2) Japanese knotweed (Fallopia japonica)

Japanese knotweed is a fast-spreading weed. It dies back in winter but quickly regenerates in early summer, shooting up bamboo-like stems over 7 feet tall, suppressing other plant growth in your gardens.

The negative/dangerous traits of Japanese knotweed:

  • Impairs the growth of surrounding plants
  • Roots penetrate pavements and house foundations
  • Can reduce the value of a house by up to 20%

How to remove Japanese knotweed from your garden

Seeking professional assistance is advisable for the removal of this invasive plant, but should you try to tackle it yourself, spray or inject the stems with approved herbicides. Repeated applications may be necessary, and typically, it requires a minimum of three years to effectively treat the knotweed.

3) Poison hemlock (Conium maculatum)

Poison hemlock is a highly toxic plant with smooth, purple-spotted stems and finely divided, fern-like leaves. It typically grows up to 6-10 feet in height. Its small, white umbrella-shaped flowers appear in clusters during the summer. This plant is infamous for its deadly poison, affecting the nervous system and often proving fatal if ingested.

The negative/dangerous traits of poison hemlock:

  • Highly toxic to humans and animals if ingested
  • Can cause respiratory failure, paralysis, and death in severe cases
  • Often mistaken for edible plants like parsley or wild carrots, leading to accidental poisoning

How to remove poison hemlock from your garden

Always wear protective clothing when handling poison hemlock. Dig out the whole plant, including the long taproot, (alternatively, glyphosate treatment can be used to eradicate the plant). Wash your hands thoroughly after bagging up the plant for removal. Continue to monitor the area for seedling growth. 

4) Chinese Wisteria (Wisteria sinensis)

This is a climbing vine known for its beautiful cascades of fragrant purple flowers. However, its rapid growth and ability to smother other plants make it a nuisance in gardens, do not be fooled by this beautiful species.

The negative/dangerous traits of wisteria:

  • It has an aggressive growth habit, which can overtake landscapes rapidly
  • It has an ability to strangle and kill trees and shrubs
  • Chinese wisteria has toxic seeds and pods, which are harmful to humans and animals if ingested
  • It can cause structural damage by growing into buildings and infrastructure, de-valuing your home

How to remove wisteria from your garden

To remove invasive wisteria safely, cut the vines close to the root and apply glyphosate or garlon to the cut stem. Dispose of cut vines properly. Alternatively, if avoiding herbicides, trim regularly until autumn or dig up the entire plant, watching for regrowth.

5) Green alkanet (Pentaglottis sempervirens)

Green alkanet is an invasive perennial with clusters of small blue flowers and rough, hairy leaves. Despite its attractive appearance, green alkanet can quickly spread and dominate garden beds, crowding out desirable plants.

The negative/dangerous traits of green alkanet:

  • It spreads extremely quickly 
  • It can smother and kill other plants in your garden
  • It’s hard to eradicate because its seeds remain in the soil for a long time
  • The hairy stems can cause skin irritation 

How to remove green alkanet from your garden

To remove green alkanet, pull or fork out seedlings from loose soil, ensuring you remove all roots. Keep an eye out for new seedlings near existing clumps. For established plants, dig out clumps with a border fork or spade, targeting the root system. S

mothering plants with cardboard and thick organic matter or using biodegradable mulch matting can also be effective. Keep the soil covered for several years to make sure it doesn’t spread again.

Other invasive plant species to watch out for in your garden

Here are some other invasive species to be mindful of and prepare for removal:

  • Rhododendron
  • Norway Maple Tree
  • Himalayan Balsam
  • English Ivy
  • Bugleweed
  • Russian Vine