Pond Alert!
Managing your garden pond to protect Scotland’s wildlife
Problem pond plants
Avoid these species for the health of your
pond and the wider countryside
Problem pond plants
Avoid these species for the health of your pond and the wider countryside
Plantlife is concerned that some pond plants
commonly used in gardens are non-native
invasive species. These plants can escape
into the wild, causing problems that are
very expensive to remedy.
The species below do not make good
residents in your garden pond because they
are fast growing and easily out-compete
other, more desirable species. However
carefully you control their growth in the
garden, they can all too easily be transported
into the wider countryside as stem fragments
on birds’ feet, pets’ paws and even human
shoes. Once in the wild, they regrow quickly,
even from tiny fragments, and their spread
can be uncontrolled. This results in them
taking over natural ponds and lochans,
crowding out native species.
Australian Swamp Stonecrop or New
Zealand Pigmyweed (Crassula helmsii,Tillaea
recurva,Tillaea helmsii)
Description: fleshy, opposite, small, thin green
leaves, with tiny white flowers from late June
to September.
Type: submerged “oxygenator”
Problem: originating from Australasia, this
extremely invasive aquatic plant forms dense
carpets and excludes all competitors. An extra
complication is that this plant is sold under a
range of different names: the most common
are given above. It can cross from pond to
pond on the roots of other aquatic plants, and
has spread at alarming pace across the UK
since 1956. Control measures have so far
proved unsuccessful.
2006 Scottish distribution: found in a few
locations throughout Scotland.
Removal tip: pull out as soon as you see it.
Regular clearing will be required.
Ä
BOB GIBBONS/NATURAL IMAGE
Australian Swamp Stonecrop or New Zealand Pigmyweed (Crassula helmsii,Tillaea recurva,Tillaea helmsii)
BOB GIBBONS/NATURAL IMAGE
Curly Waterweed (Lagarosiphon major, Elodea crispa)
PAUL STERRY/NATURE PHOTOGRAPHERS
© Canadian
Waterweed (Elodea
canadensis)
Description: green, blunt
leaves arranged in whorls
up the stem.
Type: submerged
“oxygenator”
Problem: this North
American species spreads
rapidly in a wide range of
ponds and other
freshwater habitats. It
forms dense mats that
Canadian Waterweed (Elodea canadensis)
choke ponds, out-compete
native plant life and reduce
Ä Curly Waterweed
light and oxygen in the pond.
2006 Scottish distribution: found in Moray,
(Lagarosiphon major, Elodea crispa)
Argyll and throughout the Central Lowlands.
Description: similar to Elodea canadensis with
green, blunt leaves, but they are arranged
Removal tip: thinning by uprooting is best
spirally up the stem, not in obvious whorls.
done in early spring.
Problem pond plants
Avoid these species for the health of your pond and the wider countryside
Type: submerged “oxygenator”
Problem: this southern African plant forms
dense masses in standing waters, mainly in the
southern half of Britain. It can be a pest even
in its native range.This plant is widely sold in
garden centres here, but is already banned in
New Zealand and Australia.
2006 Scottish distribution: Castle Douglas,
Edinburgh, Glasgow, Fife.
Removal tip: cut in early spring and repeat
regularly to weaken the plant.
Nuttall’s Waterweed (Elodea nuttallii)
Description: similar to Elodea canadensis, but
leaves darker green, twisted, pointed and
strongly curved back on themselves.
Type: submerged “oxygenator”
Problem: this North American species
spreads rapidly in similar habitats to, but
more nutrient enriched watercourses than,
Elodea canadensis.
Parrot’s-feather (Myriophyllum aquaticum)
Description: feathery, much branched leaves,
true to its name. Distinguished from native
Myriophyllum species by the fact that its leaves
are emergent.
Type: marginal
Problem: this South American species is
mostly found in shallow ponds although it has
been recorded in a range of water bodies,
including flowing systems. It has colonised
about 100 sites in the south of England and its
distribution is not yet as widespread in
Scotland as Crassula helmsii.
2006 Scottish distribution: Dumfries
Removal tip: uproot manually as soon as you
notice it.
Ä
BOB GIBBONS/NATURAL IMAGE
Parrot’s-feather (Myriophyllum aquaticum)
2006 Scottish distribution: Central Belt,
Dumfries.
Removal tip: thin during height of summer.
Problem pond plants
Avoid these species for the health of your pond and the wider countryside
nurseries. Sometimes sold under the misnomer
“marsh pennywort”, the common name of
Hydrocotyle vulgaris, a native British species.
2006 Scottish distribution: no records.
Removal tip: repeated cutting will be necessary.
Floating Pennywort (Hydrocotyle ranunculoides)
BOB GIBBONS/NATURAL IMAGE
Floating Pennywort
(Hydrocotyle ranunculoides)
Description: almost circular, floating leaves up
to 70mm across, with stalk at the edge.Whitish
flowers produced rarely, in July/August.
Type: floating plant
Problem: this North American plant forms
dense, interwoven mats of floating vegetation,
which grow across the surface, reducing the
amount of oxygen and light in the pond. This
has grave consequences for native plants, fish
and invertebrates, and the apparently solid
surface can be a danger to unsuspecting
humans, pets and cattle. Initial studies of the
British population show that this invasion
probably resulted from a single population made
available through aquatic garden centres and
¶
BOB GIBBONS/NATURAL IMAGE
Water Fern or Fairy Fern (Azolla filiculoides)
Water Fern or Fairy Fern
(Azolla filiculoides)
Description: similar to a large duckweed, but
with fronds overlapping along the stem, which
is branched. Turning red in autumn.
Type: floating plant
Problem: this floating fern originates from
North and South America, is often able to
survive British winters and can invade a
region rapidly excluding all competitors. It
forms dense mats and out-competes native
plants and animals. Forming apparently solid
surfaces, this plant can be a danger to
humans, pets and other animals, and also
causes problems in drainage and water
systems. The plant produces spores at the
beginning of winter or once dense mats have
formed. It also spreads easily to other water
plants in shop displays.
2006 Scottish distribution: Forth, Fife, Irvine,
Brodick
Removal tip: remove with net before spores
are released.
Ä
www.plantlife.org.uk
[email protected]
Plantlife is the UK’s leading charity working to protect
wild plants and their habitats
Plantlife Scotland, Balallan House,
Allan Park, Stirling, FK8 2QG
Tel: 01786 478509/479382
Plantlife International – The Wild Plant Conservation Charity is a charitable company limited by guarantee.
Registered Charity Number: 1059559 Registered Company Number: 3166339. Registered in England
ISBN: 1 904749-61-5 © February 2007
DESIGN: RJPDESIGN.CO.UK
Disposal tips:
● There is no magic solution for removing
overgrown pond plants. Pulling them out at
regular intervals will cause least disturbance
to the rest of the pond.
● Once plants have been removed they should
be left at the edge of the pond for a few
hours or overnight to allow small pond
creatures to get back to the pond.
● Transfer the removed plants to the
compost heap. Leaving them for too long
will cause too many nutrients to leach back
into the pond.
● Other control options include increasing
the amount of shade over the pond, using
plants such as Bogbean and making sure that
nutrients do not get into the pond, from
lawn/plant feed for example.
● Do not put any excess pond plants into
ponds, lochs, rivers, streams or drains.
Always compost them or put them in your
garden waste bin.
COVER PICTURE BY BOB GIBBONS/NATURAL IMAGE
What can I do?
● Ask your local garden centre for alternative
species, more suited to the Scottish climate
and countryside. See Plantlife’s Alternative
plants leaflet, also available at
www.plantlife.org.uk
● Carefully rinse any new aquatic plants over
a bucket, as fragments of non-native invasive
species may have contaminated them. Pour
the water and washed off fragments on your
compost heap or on your flowerbeds.