Potentially invasive plants
There are many edible and ornamental plants, readily available to buy in garden centres, that have the potential to become a nuisance in the right conditions in UK gardens. This page covers common ‘garden thugs’ and how you can control them.
Quick facts
- Plants may be considered thuggish due to their large size, spreading habit or ability to self-seed prolifically
- Common UK garden thugs include Leyland cypress, Japanese anemones, houttuynia, blackberries and mint
- Most concern is given to non-native plants escaping into the wild, but gardeners will find native plants can grow more than wanted too
- Plants that have already escaped cultivation, and pose a threat to natural habitats, are regulated under UK law
- There are several non-chemical ways to control or remove potentially invasive plants, if needed
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What are potentially invasive plants?
So-called ‘garden thugs’ are plants that can quickly get out of hand in a garden, either due to a very vigorous growth rate or an ability to spread easily. Unlike weeds, which tend to arrive unaided from neighbouring countryside or wasteland, ‘garden thugs’ are often widely sold in garden centres and deliberately planted for their edible or ornamental value.
Many potentially invasive plants are widely available for sale
Many of these plants tolerate a wide range of growing conditions but grow and spread particularly fast in certain places, for example where the soil is moist and there is plenty of sunshine. They may be well-behaved in some gardens but troublesome in others, and more prevalent in some parts of the country, such as the drier south or wetter west, depending on their ideal growing conditions.
Found any plants to be thugs in your garden? You can let researchers know by logging the details with Plant Alert.
Common non-native garden thugs
Some of the most common potentially invasive plants include:
Trees
- Cherry laurel (Prunus laurocerasus)
- False acacia (Robinia pseudoacacia)
- Leyland cypress (× Cuprocyparis leylandii)
- Poplars (Populus spp.)
Shrubs
- Japanese rose (Kerria japonica)
- Snowberry (Symphoricarpos spp.)
- Sorbaria spp.
- Sumach (Rhus spp.)
- Two-flowered raspberry (Rubus biflorus)
Climbers
- Passion flower (Passiflora caerulea)
- Russian vine (Fallopia baldschuanica)
Bamboo
- Arrow bamboo (Pseudosasa japonica)
- Narihira bamboo (Semiarundinaria fastuosa)
- Phyllostachys spp.
- Sasa and Sasaella spp.
- Other 'running types' (see our bamboo growing guide)
Herbaceous perennials
- Bear's breeches (Acanthus spp.)
- Burnet (Sanguisorba spp., particularly S. canadensis)
- Canadian goldenrod (Solidago canadensis)
- Chinese lantern (Physalis alkekengi)
- Comfrey (Symphytum spp.)
- Dotted loosestrife (Lysimachia punctata)
- False lupin (Thermopsis montana)
- Gardener's garters (Phalaris arundinacea var. picta)
- Giant butterbur (Petasites japonicus)
- Green alkanet (Pentaglottis sempervirens)
- Heart-leaved houttuynia (Houttuynia cordata)
- Japanese anemone (Anemone × hybrida)
- Montbretia (Crocosmia spp.)
- Plume poppy (Macleaya spp.)
- Purple top (Verbena bonariensis)
- Queen of the prairie (Filipendula rubra)
- Sisyrinchium spp.
Ground cover plants
- Creeping wood sorrel (Oxalis corniculata)
- Cypress spurge (Euphorbia cyparissias)
- Greater periwinkle (Vinca major)
- Leptinella (Leptinella squalida)
- Mind-your-own-business (Soleirolia soleirolii)
- Rose of Sharon (Hypericum calycinum)
- Winter heliotrope (Petasites fragrans)
Bulbous plants
Edible Plants
- Horseradish (Armoracia rusticana)
- Jerusalem artichoke (Helianthus tuberosus)
- Mint (Mentha spp.)
Pond and bog plants
- Bulrush (Typha laxmannii and T. minima)
- Hart's pennyroyal (Mentha cervina)
- Sensitive fern (Onoclea sensibilis)
- Many other vigorous aquatic plants (see our page on aquatic weeds)
Common native garden thugs
There are also many native plants that grow too large or spread too quickly for an average garden, these include:
Trees
- Aspen (Populus tremula)*
- Black poplar (Populus nigra)*
Herbaceous perennials
- Common comfrey (Symphytum officinale)*
- Great burnet (Sanguisorba officinalis)*
- Pendulous sedge (Carex pendula)*
- Reed canary grass (Phalaris arundinacea)*
- Soapwort (Saponaria officinalis)***
- Wood spurge (Euphorbia amygdaloides)**
Ground cover plants
- Bugle (Ajuga spp.)*
- Creeping Jenny (Lysimachia nummularia)*
- Lesser periwinkle (Vinca minor)***
- Sweet woodruff (Galium odoratum)*
- Yellow archangel (Lamium galeobdolon)*
Bulbous plants
- Bluebell (Hyacinthoides non-scripta)*
- Italian arum (Arum italicum and subsp.)**
- Lesser celandine (Ficaria verna and subsp.)*
Edible plants
- Apple mint (Mentha suaveolens)**
- Blackberries (Rubus fruticosus)*
- Chives (Allium schoenoprasum)*
- Fennel (Foeniculum vulgare)***
- Raspberries (Rubus idaeus)*
- Spearmint (Mentha spicata)***
Pond and bog plants
- Amphibious bistort (Persicaria amphibia)*
- Branched bur reed (Sparganium erectum)*
- Bulrush (Typha latifolia)*
- Common reed (Phragmites australis)*
- Lesser bulrush (Typha angustifolia)*
- Pennyroyal (Mentha pulegium)*
- Reed sweet grass (Glyceria maxima)*
- Water mint (Mentha aquatica)*
- White waterlily (Nymphaea alba)*
- Yellow iris (Iris pseudacorus)*
- Yellow waterlily (Nuphar lutea)*
*Native to the UK (Great Britain & Ireland)
**Native to Great Britain only
***Archeophyte (a plant introduced before 1500 and considered naturalised)
While these native plants may need controlling to limit their size and spread, and stop them becoming a nuisance, there is no need to worry about them escaping into the countryside. On the other hand, non-native plants pose a significant risk if they escape from our gardens, as they can outcompete and displace native species as well as alter natural ecosystems.
Why are these plants troublesome?
Garden plants may be considered potentially invasive if they:
- Grow very quickly – plants like Leyland cypress and Russian vine grow so quickly that they can fast become too big for an average garden and can easily smother and outcompete other plants.
- Readily produce suckers – some trees and shrubs, like poplars and sumach, send up new shoots over a large area. These may appear in borders and lawns, and cross boundaries into neighbouring gardens.
- Spread by creeping rhizomes or rooting stems – many groundcover plants, like winter heliotrope, periwinkle and mind-your-own-business, can cover a large area and grow among and into other plants. The rhizomes of ‘running’ bamboos may grow several metres from the parent plant.
- Form large clumps or thickets – some perennials, like Japanese anemones, dotted loosestrife and gardener’s garters, form ever-enlarging clumps that can take over borders and overwhelm other plants.
- Self-seed abundantly – several garden plants, like purple top, pendulous sedge and fennel, are prolific self-seeders, and you may find large numbers of seedlings appearing throughout a border or around the garden.
- Produce offsets – some plants, like bluebells and creeping wood sorrel, produce offsets which are easily detached and spread around a garden.
How do I control potentially invasive plants?
If you need to control the size or spread of 'garden thugs', try the following:
- Carefully consider the planting location – many garden thugs are only a problem in ‘favourable’ growing conditions, such as a reliably moist soil or warm, sheltered spot. Planting in less favourable conditions, such as a drier soil or partly shaded area, often helps to limit vigour and spread, while still allowing you to enjoy the plant. Grow plants that spread by rhizomes, such as mint, in containers to prevent them spreading.
- Control the size of vigorous plants – prune trees, shrubs and climbers to keep them at a smaller size and divide herbaceous perennials to reduce the size of a clump. Check the best time to do this by consulting a good pruning or propagating book, following the above plant links or contacting RHS Gardening Advice if you are an RHS member.
- Deadhead promptly – limit the spread of self-seeding plants by removing spent flowers before they run to seed. This often has the added bonus of encouraging more flowers.
- Remove or supress seedlings – look out for seedlings of thuggish plants appearing in spring and use a hand fork to remove them before they become established. Alternatively, mulch bare soil with a 20cm (8in) thick layer of organic matter to reduce germination and smother seedlings.
- Minimise soil disturbance – avoid hoeing and digging around plants with creeping stems, rhizomes or offsets, as this can encourage further spread, and take care not to move soil from this part of your garden, as you could unintentionally spread them further.
- Dig out unwanted plants – if you are struggling to control a thuggish plant, use a sharp spade and border fork to remove it, taking care to find as many roots, rhizomes or offsets as possible. You may need to hire a professional to remove large trees, shrubs or climbers.
- Dispose of garden waste carefully – don’t add the seedheads, rhizomes, tough roots or bulbs of thuggish plants to your home compost bin, as it may not reach high enough temperatures to kill them. Instead, put them in your council green waste recycling bin or take them to your local recycling site.
Should I use weedkiller to control garden thugs?
No – the vast majority of thuggish garden plants can be controlled or removed using the non-chemical options above. The invasive nature of these plants means that many will be resistant to weedkiller, or several applications would be needed to have any marked effect.
Get involved
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