Ed Seeley
Member
ALIEN INVASIVE SPECIES WHICH THREATEN THE UK’S FLORA
This thread is taken from Plantlife web pages (Original Web Page) and it lists the 20 most damaging aquatic and terrestrial invasive aliens, describes the problems they cause, gives an indication of their spread in Britain based on New Atlas data (Preston et al., 2002) and proposes a range of control options. The control options include:
• Create zones free of certain alien invasive species
• Containment or eradication on selected sites of nature conservation importance
• Early detection and eradication
• Remove plant from sale
• Improved labelling and guidance for gardeners
• Place on Schedule 9 Part II
These are the Aquatic Plants that are covered by this;
1. Azolla filiculoides Water fern
Origin North and South America
Description of the problem This floating fern is able to survive the harsh British winters and can invade a region very rapidly excluding all competitors.
Atlas Change index +2.76
Cultivation date Not known
First date in wild in GB 1886
10km2 occurences in GB 577
Action proposed Eradication on selected sites of nature conservation importance
Create Azolla free zones, eg. Scotland
Remove plant from sale
Place on Schedule 9 Part II
2. Cabomba caroliniana Fanwort
Origin Eastern North and southern South America
Description of the problem Cabomba is widely sold as an aquarium plant, mainly from nursery stock in Holland. It was found in Forth and Clyde Canal in 1969 but is no longer present; then in the Basingstoke canal 1991-95. It reproduces by rooting of stem fragments.
Atlas Change index N/A
Cultivation date Not known
First date in wild in GB 1969
10km2 occurences in GB 0
Action proposed Early detection and eradication
Remove plant from sale
4. Crassula helmsii Australian swamp stonecrop
Origin Australasia
Description of the problem This extremely invasive aquatic plant has spread at alarming pace across Britain since its establishment in 1956. It forms dense carpets and excludes all competitors. It is threatening the survival of starfruit Damasonium alisma, one of Britain’s rarest plant. The advance of this weed, which was introduced from Australasia in 1911, has been carefully monitored. It has spread at alarming pace across the country and control measures have to date proved unsuccessful. Even so, the cost of adequate control is estimated to be about £3,000,000 (Leach and Dawson, 1999). An extra complication is the fact that this plant is sold under a range of different names. Some aquatic nurseries have confused the issue by referring to it as Tillaea recurva, or Tillaea helmsii. It also has a variety of English names including New Zealand swamp stonecrop.
Atlas Change index N/A
Cultivation date 1927
First date in wild in GB 1956
10km2 occurences in GB 574
Action proposed Eradication on selected sites of nature conservation importance
Create Crassula free zones, eg. Scotland
Remove plant from sale
Place on Schedule 9 Part II
5. Eichhornia crassipes Water hyacinth
Origin South America
Description of the problem Has damaged aquatic habitats wherever it has been introduced. Not yet established in the wild in Britain, but cold water varieties known and being developed in Holland.
Atlas Change index N/A
Cultivation date Not known
First date in wild in GB -
10km2 occurences in GB 0
Action proposed Early detection and eradication
Remove plant from sale
6. Hydrocotyle ranunculoides Floating pennywort
Origin North America
Description of the problem The plant forms dense, interwoven mats of floating vegetation which grow across the surface, altering the ecology of the water body. Initial studies of the British population show that this invasion probably resulted from a single population made available through aquatic garden centres and nurseries where it was often sold under the misnomer “marsh pennywortâ€, the common name of H. vulgaris, a native British species (Newman and Dawson, 2000). The species is causing a “multitude of problems including deoxygenation of the underlying water, killing fish and invertebrates, drowning cattle and choking drainage systems and sluices, causing extensive localised flooding…crowding out our native plants such as Frogbit, Duckweed and Water Crowfoot†(English Nature, 1999). The current estimate for control of the total infested area by herbicides is between £250,000 and £300,000 per year.
Atlas Change index N/A
Cultivation date Not known
First date in wild in GB 1990
10km2 occurences in GB 43
Action proposed Early detection and eradication
Remove plant from sale
Place on Schedule 9 Part II
7. Lagarosiphon major Curly waterweed
Origin Southern Africa
Description of the problem Forms dense masses in standing waters. Mainly in southern half of Britain. Can be a pest even in its native range. Sold in garden centres. Banned from New Zealand and Australia.
Atlas Change index N/A
Cultivation date Not known
First date in wild in GB 1944
10km2 occurences in GB 385
Action proposed Eradication on selected sites of nature conservation importance
Create Lagarosiphon free zones, eg. Scotland
Remove plant from sale
Place on Schedule 9 Part II
8. Myriophyllum aquaticum Parrot’s-feather
Origin South America
Description of the problem It is mostly found in shallow ponds although has been recorded in a range of water bodies, including flowing systems. It has colonised only about 100 sites in the south of England and its distribution is not yet as widespread as Crassula helmsii. Parrot’s feather does not normally produce the numerous small vegetative fragments which act as propagules in C. helmsii (Preston and Croft, 1997), although regrowth from stem fragments is assumed to be a major factor in the dispersal strategy of the species. It currently threatens one of the six remaining sites in the UK of the Red Data Book species brown gallingale Cyperus fuscus.
Atlas Change index N/A
Cultivation date 1878
First date in wild in GB 1960
10km2 occurences in GB 268
Action proposed Eradication on selected sites of nature conservation importance
Create Myriophyllum free zones & maintain Scotland as a Myriophyllum free zone
Remove plant from sale
Place on Schedule 9 Part II
9. Pistia stratiotes Water lettuce
Origin South America
Description of the problem A free-floating plant with thick leaves and long dense roots, which when introduced to North America caused extensive weed management problems. Observed in Nottingham in 1999, but unlikely to overwinter at the moment
Atlas Change index N/A
Cultivation date Not known
First date in wild in GB -
10km2 occurences in GB 0
Action proposed Early detection and eradication
Remove plant from sale
10. Salvinia molesta Giant salvinia
Origin Brazil
Description of the problem This free-floating aquatic fern is one of the most loathed plants in the US. It has spread to many of the aquatic systems as far north as North Carolina. It has already been spotted in the UK in Lincolnshire. S. auriculata is much prettier than S. molesta and it will not be long before it is also stocked
Atlas Change index N/A
Cultivation date Not known
First date in wild in GB -
10km2 occurences in GB 0
Action proposed Early detection and eradication
Remove plant from sale
The plants we should be really careful with are the ones that have been placed on the Schedule 9 list as these have shown the ability to be very invasive and cause quite serious problems either to native species or the waterways themselves. The other species are ones that we should be careful when disposing of them or make sure we don't keep them anywhere where they could possibly get into the outside environment. If everyone did this then their use in our tropical tanks wouldn't be a problem and the recommendations to remove these plants from sale could be lifted.
This thread is taken from Plantlife web pages (Original Web Page) and it lists the 20 most damaging aquatic and terrestrial invasive aliens, describes the problems they cause, gives an indication of their spread in Britain based on New Atlas data (Preston et al., 2002) and proposes a range of control options. The control options include:
• Create zones free of certain alien invasive species
• Containment or eradication on selected sites of nature conservation importance
• Early detection and eradication
• Remove plant from sale
• Improved labelling and guidance for gardeners
• Place on Schedule 9 Part II
These are the Aquatic Plants that are covered by this;
1. Azolla filiculoides Water fern
Origin North and South America
Description of the problem This floating fern is able to survive the harsh British winters and can invade a region very rapidly excluding all competitors.
Atlas Change index +2.76
Cultivation date Not known
First date in wild in GB 1886
10km2 occurences in GB 577
Action proposed Eradication on selected sites of nature conservation importance
Create Azolla free zones, eg. Scotland
Remove plant from sale
Place on Schedule 9 Part II
2. Cabomba caroliniana Fanwort
Origin Eastern North and southern South America
Description of the problem Cabomba is widely sold as an aquarium plant, mainly from nursery stock in Holland. It was found in Forth and Clyde Canal in 1969 but is no longer present; then in the Basingstoke canal 1991-95. It reproduces by rooting of stem fragments.
Atlas Change index N/A
Cultivation date Not known
First date in wild in GB 1969
10km2 occurences in GB 0
Action proposed Early detection and eradication
Remove plant from sale
4. Crassula helmsii Australian swamp stonecrop
Origin Australasia
Description of the problem This extremely invasive aquatic plant has spread at alarming pace across Britain since its establishment in 1956. It forms dense carpets and excludes all competitors. It is threatening the survival of starfruit Damasonium alisma, one of Britain’s rarest plant. The advance of this weed, which was introduced from Australasia in 1911, has been carefully monitored. It has spread at alarming pace across the country and control measures have to date proved unsuccessful. Even so, the cost of adequate control is estimated to be about £3,000,000 (Leach and Dawson, 1999). An extra complication is the fact that this plant is sold under a range of different names. Some aquatic nurseries have confused the issue by referring to it as Tillaea recurva, or Tillaea helmsii. It also has a variety of English names including New Zealand swamp stonecrop.
Atlas Change index N/A
Cultivation date 1927
First date in wild in GB 1956
10km2 occurences in GB 574
Action proposed Eradication on selected sites of nature conservation importance
Create Crassula free zones, eg. Scotland
Remove plant from sale
Place on Schedule 9 Part II
5. Eichhornia crassipes Water hyacinth
Origin South America
Description of the problem Has damaged aquatic habitats wherever it has been introduced. Not yet established in the wild in Britain, but cold water varieties known and being developed in Holland.
Atlas Change index N/A
Cultivation date Not known
First date in wild in GB -
10km2 occurences in GB 0
Action proposed Early detection and eradication
Remove plant from sale
6. Hydrocotyle ranunculoides Floating pennywort
Origin North America
Description of the problem The plant forms dense, interwoven mats of floating vegetation which grow across the surface, altering the ecology of the water body. Initial studies of the British population show that this invasion probably resulted from a single population made available through aquatic garden centres and nurseries where it was often sold under the misnomer “marsh pennywortâ€, the common name of H. vulgaris, a native British species (Newman and Dawson, 2000). The species is causing a “multitude of problems including deoxygenation of the underlying water, killing fish and invertebrates, drowning cattle and choking drainage systems and sluices, causing extensive localised flooding…crowding out our native plants such as Frogbit, Duckweed and Water Crowfoot†(English Nature, 1999). The current estimate for control of the total infested area by herbicides is between £250,000 and £300,000 per year.
Atlas Change index N/A
Cultivation date Not known
First date in wild in GB 1990
10km2 occurences in GB 43
Action proposed Early detection and eradication
Remove plant from sale
Place on Schedule 9 Part II
7. Lagarosiphon major Curly waterweed
Origin Southern Africa
Description of the problem Forms dense masses in standing waters. Mainly in southern half of Britain. Can be a pest even in its native range. Sold in garden centres. Banned from New Zealand and Australia.
Atlas Change index N/A
Cultivation date Not known
First date in wild in GB 1944
10km2 occurences in GB 385
Action proposed Eradication on selected sites of nature conservation importance
Create Lagarosiphon free zones, eg. Scotland
Remove plant from sale
Place on Schedule 9 Part II
8. Myriophyllum aquaticum Parrot’s-feather
Origin South America
Description of the problem It is mostly found in shallow ponds although has been recorded in a range of water bodies, including flowing systems. It has colonised only about 100 sites in the south of England and its distribution is not yet as widespread as Crassula helmsii. Parrot’s feather does not normally produce the numerous small vegetative fragments which act as propagules in C. helmsii (Preston and Croft, 1997), although regrowth from stem fragments is assumed to be a major factor in the dispersal strategy of the species. It currently threatens one of the six remaining sites in the UK of the Red Data Book species brown gallingale Cyperus fuscus.
Atlas Change index N/A
Cultivation date 1878
First date in wild in GB 1960
10km2 occurences in GB 268
Action proposed Eradication on selected sites of nature conservation importance
Create Myriophyllum free zones & maintain Scotland as a Myriophyllum free zone
Remove plant from sale
Place on Schedule 9 Part II
9. Pistia stratiotes Water lettuce
Origin South America
Description of the problem A free-floating plant with thick leaves and long dense roots, which when introduced to North America caused extensive weed management problems. Observed in Nottingham in 1999, but unlikely to overwinter at the moment
Atlas Change index N/A
Cultivation date Not known
First date in wild in GB -
10km2 occurences in GB 0
Action proposed Early detection and eradication
Remove plant from sale
10. Salvinia molesta Giant salvinia
Origin Brazil
Description of the problem This free-floating aquatic fern is one of the most loathed plants in the US. It has spread to many of the aquatic systems as far north as North Carolina. It has already been spotted in the UK in Lincolnshire. S. auriculata is much prettier than S. molesta and it will not be long before it is also stocked
Atlas Change index N/A
Cultivation date Not known
First date in wild in GB -
10km2 occurences in GB 0
Action proposed Early detection and eradication
Remove plant from sale
The plants we should be really careful with are the ones that have been placed on the Schedule 9 list as these have shown the ability to be very invasive and cause quite serious problems either to native species or the waterways themselves. The other species are ones that we should be careful when disposing of them or make sure we don't keep them anywhere where they could possibly get into the outside environment. If everyone did this then their use in our tropical tanks wouldn't be a problem and the recommendations to remove these plants from sale could be lifted.