Know what you grow

Be plant wise to the threat of invasive plants, which can take over your pond and damage the environment. Ask for help picking the right plants for the size and purpose of your pond and ask how to care for them properly.

Here are five examples of invasive aquatic plants that you might find in your pond. If you do discover an invasive species, don't panic - just be plant wise and remember to dispose of any unwanted plants by composting them.

Charlie Dimmock is supporting the Be Plant Wise campaign by encouraging pond owners to compost unwanted pond plants.

Female holding up weeds in hands

Alternative plants

Find out more about the alternative plants you can use for your pond.

Links to all the aquatic plant ID sheets

Links to other non-native aquatic plant species, as well as other plants and animals.

Information on five of the key invasive aquatic plants

Floating pennywort (also sold as water pennywort or simply pennywort)

(Hydrocotyle ranunculoides)

Floating pennywort was first introduced into Britain from North America in the 1980s and was present in the wild by 1990. It is now known to be present in at least 150 different locations in England and Wales, but none yet in Scotland.

Where it has escaped into the wild it is usually found in slow-flowing water on the edges of rivers and lakes and in ditches. It forms dense interwoven mats of vegetation. These can look like solid land and so be a danger to children and livestock. This plant grows faster than most native aquatic plants, blocks out light and can stop fish accessing feeding and resting spaces. It can also cause localised flooding by blocking drainage systems as well as affecting the amenity of a waterbody by interfering with activities such as angling and boating. Floating pennywort can grow very quickly - up to 20cm a day.

Features

  • Shiny, kidney-shaped leaves with crinkled edges, up to 7cm across.
  • Usually found floating on the surface of still or slow moving water where it has escaped into the wild.

Impacts

  • Currently known to be present in at least 150 different locations in England and Wales, but none yet in Scotland.
  • Can grow up to 20cm per day and may quickly dominate a waterbody.
  • Forms thick mats which can look like dry land and so be a danger to people and livestock.
  • Impedes water flow and chokes waterways which can make it difficult for boats and angling and can increase the risk of flooding.
  • Poses a threat to plants and fish by blocking out light and impeding access to fish feeding and resting spaces.

It is easy to confuse this plant with other species. You can use our identification sheets to help you make sure you've identified them correctly, or ask your pond plant retailer for help.

Advice on how to manage this species can be found here
Download a detailed identification sheet for floating pennywort
View more images of Floating pennywort in the NNSS image gallery

Parrot's feather (also sold as Brazilian water-milfoil or as 'oxygenator')

(Myriophyllum aquaticum, Myriophyllum brasiliense, Myriophyllum proserpinacoides)

Parrot's feather is native to Central and South America and has been grown in water gardens in the UK since 1878. It was first recorded in the wild in 1960, where it was most likely spread due to improper disposal from garden ponds. It is now prevalent in the south of England and spreading northwards, though it is still rare in Scotland at the moment.

Where it has escaped into the wild it is found in still and slow-flowing water and can be submerged or emerging from the surface of water. It persists throughout the winter and can be found growing on land when ponds dry out. It is usually bought as an oxygenating plant and to provide cover and food for fish. It can rapidly dominate a water body, creating a thick raft of vegetation which can displace native species. It can contribute to localised flooding by blocking watercourses and drainage channels. Parrot's feather is distinctive because of its blue-green colour, feather-like leaves and emergent stems. A fragment as small as 5mm can re-grow.

Features

  • Is able to keep growing when ponds dry out.
  • Leaves have a characteristic feathery appearance and are bright green to blue-grey.
  • Grows both under the water and emerging from the water.
  • Usually found growing as a marginal plant in still or slow-moving nutrient-rich water.

Impacts

  • Currently a problem in the South of England but is found in northern areas too where it is likely to become more of a problem.
  • Produces a thick raft of vegetation.
  • A fragment as small as 5mm can re-grow.
  • Poses a threat to plants and fish by blocking out light and reducing oxygen levels in the water.
  • Can choke waterways so increasing the risk of flooding.

It is easy to confuse this plant with other species. You can use our identification sheets to help you make sure you've identified them correctly, or ask your pond plant retailer for help.

Advice on how to manage this species can be found here
Download a detailed identification sheet for parrot's feather
View more images of Parrot's feather in the NNSS image gallery

New Zealand pigmyweed (also known as Australian swamp stonecrop)

(Crassula helmsii - also sold incorrectly as Crassula recurva, Tillaea recurva and Tillaea helmsii).

New Zealand pigmyweed was introduced into Britain from Australasia in 1911 as an oxygenating plant for ponds and, since the 1970s, has spread rapidly. It is widespread in Wales and England - particularly in the South-East - but much less common in Scotland at the moment.

Where it has escaped into the wild, New Zealand pigmyweed is found in slow-flowing or still water that is up to 3m deep such as ditches and on the edges of lakes, where it forms dense vegetative mats that out-compete most native aquatic plants. This can lead to large fluctuations of oxygen in the water body and the blocking out of light, affecting other plants, fish and invertebrates as well as increasing the risk of localised flooding by blocking drainage systems. New Zealand pigmyweed grows both in and under water as well as on land by water. It is readily recognisable when growing at the edges of water bodies by its fleshy leaves, but is less easy to see when submerged under water. Its submerged form can look quite different to its land form, so check out our identification sheet. It produces tiny white flowers from July to September.

Features

  • Frost resistant.
  • Grows both in and under the water as well as on land by water.
  • Readily recognisable when growing at the edges of water by its narrow fleshy bright green leaves.
  • Tiny white flowers are present from July to September.

Impacts

  • Currently a widespread problem in England and Wales and starting to become more of a problem in Scotland.
  • Can regenerate from tiny fragments and therefore easily takes over new areas.
  • Forms very dense mats which overgrow native plants and reduces light levels.

It is easy to confuse this plant with other species. You can use our identification sheets to help you make sure you've identified them correctly, or ask your pond plant retailer for help.

Advice on how to manage this species can be found here
Download a detailed identification sheet for New Zealand pigmyweed
View more images of New Zealand pigmyweed in the NNSS image gallery

Water primrose

(Ludwigia grandiflora, Ludwigia uruguayensis or Ludwigia peploides also sold incorrectly as Jussiaea).

These types of water-primrose were introduced to Europe from South America as ornamental and water garden plants. They have only been recorded at a few sites in the UK, but in France, where they are much more widespread, they are causing considerable damage and costing several million Euros a year to control.

Where they have escaped into the wild they are found in still or slow-flowing water, and grow into thick carpets which can cause severe problems, including out-competing native species and clogging waterways. They spreads across the surface of the water from the banks of ponds and rivers and are easiest to identify from July to August when their bright yellow, five-petalled flowers are on show. They spread primarily by fragmentation.

Features

  • Has bright yellow flowers with five petals from July to August.
  • Floats on the surface of the water and also on the banks of ponds and rivers.

Impacts

  • Currently only recorded from a few sites in England and Wales.
  • Grows into a thick carpet which can out-grow native species and clog waterways.

It is easy to confuse this plant with other species. You can use our identification sheets to help you make sure you've identified them correctly, or ask your pond plant retailer for help.

Advice on how to manage this species can be found here
Download a detailed identification sheet for water primrose
View more images of Water primrose in the NNSS image gallery

Water fern (also known as fairy fern)

(Azolla filiculoides).

Water fern is a floating aquatic plant native to tropical America and is the only floating fern in Britain. The leaves of water fern are no bigger than 2.5mm - forming small plants around 2.5cm long which cluster to form a dense mat. Water fern floats on the surface of the water by means of numerous, small, closely-overlapping scale-like leaves, with their roots hanging in the water.

Water fern can readily take over areas of freshwater, and grow at great speed - doubling its biomass every two to three days. It is green in summer but usually turns a distinctive reddish colour in autumn and winter. When this plant completely covers the water surface, it can be a danger to children, pets and livestock who may attempt to walk on it. It also reduces oxygen levels in the water. As each individual plant is so small, it is known to be transported on other plants as a contaminant.

Features

  • Small leaves form dense clusters, spreading out along the surface of the water.
  • Grows at great speed, doubling its biomass every two to three days.
  • The only floating fern in Great Britain.

Impacts

  • A problem in England and Wales, less so in Scotland at the moment.
  • Produces a thick mat of floating vegetation.
  • Danger can lie when people and livestock attempt to walk on it.
  • The plants are so small, at no bigger than 2.5cm, that it can easily be transported on other plants as a contaminant.
  • Reduces oxygen levels in the water.

It is easy to confuse this plant with other species. You can use our identification sheets to help you make sure you've identified them correctly, or ask your pond plant retailer for help.

Advice on how to manage this species can be found here
Download a detailed identification sheet for water fern
View more images of Water fern in the NNSS image gallery

Alternative plants

There are plenty of alternative plants you can use for your pond. Which plants are best will depend on what kind of pond you have and where you are in the country. Talk to your pond plant retailer and ask them for advice on which species are most suitable and won't become invasive or escape into the wild.

For other sources of advice on which plants to use in your pond visit:


Whatever plants you put in your pond, the most important thing to remember is to dispose of them carefully by composting them or putting them in your green waste bin. You should also make sure you don't let them escape out of your pond into the wild. You may spread plants by accident as it only takes a tiny fragment for a plant to re-grow, so do take extra care to keep every tiny piece under control by cleaning your equipment, especially your footwear, after you've been managing your pond.

If friends give you cuttings it can be difficult to tell what you're getting and you could end up with an invasive plant in your pond. They may also be carrying hitch-hikers - small fragments of other plants that could start to grow and become invasive. It is better to buy your plants from a reputable retailer who should be able to tell you exactly what you're getting and provide advice on managing your pond.

Plants that you buy for your pond could be carrying hitch-hikers too. You can avoid these by washing your plants in a bucket before putting them in the pond, then emptying the bucket over the lawn or flower bed away from any watercourses or drains that flow into them.

You must never collect plants from the wild. This can be illegal and may damage the environment.


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