Here today, here tomorrow? Horizon scanning for invasive non-native plants Invasive non-native plants: what’s the big deal? Invasive non-native species are considered to pose one of the greatest threats to biodiversity and the economic-wellbeing of our planet. The problems caused by invasive non-native plants can affect our lives, for example by reducing crop yields, producing skin-burning sap or increasing risks of flooding.
Dealing with the problems caused by Invasive plants compete with other invasive species costs our economy plants for light, space and nutrients, around £2 billion every single year. often suppressing native species. Much of this money is spent on The environmental damage caused containing spread and limiting further by invasive non-native plants can be damage rather than eliminating the irreversible. At Lound Lakes on the problem altogether, eradication now Norfolk/Suffolk border a threatened being considered unattainable for a native fern, pillwort Pilularia number of invasive species that are globulifera, has been lost whilst the already widespread. invasive New Zealand pigmyweed Invasive plants damage natural Crassula helmsii now flourishes. This habitats too. They can reduce the same invasive plant is thought to have light and heat reaching lower-growing led to the loss of the great crested newt plants, alter rates of nutrient cycling, Triturus cristatus at a pond in Dorset. or (in freshwater systems) cause large Britain’s population of the great crested fluctuations in oxygen availability, newt is internationally important and all of which can be harmful to other it is a protected species. The threat plants and animals. Invasive non- posed by New Zealand pigmyweed is native rhododendron Rhododendron considered so great that some ponds ponticum, for example, poisons the soil are being filled in by conservationists around it so that other plants cannot upon its arrival as a preventative grow there. Over time it often becomes measure intended to minimise damage the only plant growing in an area. Like to other nearby ponds and streams. a number of invasive non-native plants, rhododendron provides little food for our native animals so when it takes over a habitat the space for our wildlife to live in and eat from is diminished.
Front cover image: Invasive parrot’s-feather spreads into the New Forest Important Plant Area affecting the rare native fern pillwort. © Trevor Renals
2 HERE TODAY, HERE TOMORROW? Our internationally important Atlantic Woodlands are being damaged by invasive non-native plants. © Su Cooper/Plantlife
Sites In Peril - pages 4-7 described here - the very existence of In the first part of this report we profile plant and animal species may be at stake. a selection of 20 Sites In Peril – areas Regardless, the most cost effective that are threatened, or already being and least environmentally damaging damaged, by invasive non-native plants. approach to solving the problems The selection includes a number of caused by non-native invasive plants outstanding hotspots for botanical is by preventing them from escaping diversity as well as the homes of some into the wild in the first place. But over of our endemic plants and animals 70,000 different types of non-native (species that live nowhere else on earth). plants are grown in Britain and only a Sites of Special Scientific Interest, small number of these are likely to cause National Nature Reserves, National damage to wildlife and the countryside. Parks, Special Areas of Conservation, Imposing restrictions on all these plants and Ramsar sites are all affected. would be unfair and disproportionate. There are hundreds of sites across Horizon scanning for new Britain where problem plants are invasive plants - pages 8-18 present. Curly waterweed Lagarosiphon In the second part of this report we major (often sold as Elodea crispa), describe research undertaken to try to for example, is found in 392 10km identify which non-native plants may squares in the UK (it could be present at become invasive in the future. This section one or several sites within each 10km provides a summary of the more detailed square), and New Zealand pigmyweed report Horizon scanning for invasive non- is recorded from 582 10km squares. native plants in Great Britain, which is The impact of invasive plants varies from available online from Natural England’s site to site. At times it is the social and or Plantlife’s website, or upon request. financial impacts that are most felt, for Plantlife considers a number of non- example when anglers can no longer fish native plants to be on the brink of in a river swamped by invasive plants becoming invasive in Britain and a or when the arrival of such plants mean selection of these are highlighted in this land managers are hit with additional section as ‘Ones to watch’ (pages 10-11). management costs. At other times – including at some of the Sites In Peril
HORIZON SCANNING FOR INVASIVE NON-NATIVE PLANTS 3 16 16 20 key 16 Sites In Peril
16 16 16 6
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Invasive plants aren’t the only problem affecting many of these 10 sites – indeed sometimes it is because our countryside is being 8 damaged in other ways, for example by pollution, that problem plants are able to grow so prolifically at a site. The eutrophication of a pond containing brown galingale 17 on Staines Moor SSSI (Surrey) 7 has facilitated the dense growth 14 2 20 of a number of invasive plants, 9 5 3 including New Zealand pigmyweed and parrot’s-feather, which now 12 dominate large sections of the pond. 1 15 4
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Threat status of plants in Britain using international IUCN criteria Critically Endangered - considered to be facing an extremely high risk of extinction in the wild Endangered - considered to be facing a very high risk of extinction in the wild Vulnerable – considered to be facing a high risk of extinction in the wild Near Threatened - close to qualifying for or is likely to qualify for a threatened category (Vulnerable/ Endangered/ Critically Endangered) in the near future
4 HERE TODAY, HERE TOMORROW? 1 Pevensey Levels 4 Torbay Limestones Invasive floating pennywortHydrocotyle ranunculoides can grow up The autumn squill – Portland spurge Scilla autumnalis-Euphorbia to 20cm per day. Together with New Zealand pigmyweed Crassula portlandica fescue grassland at Torbay Limestones is one of the helmsii it now smothers 45km of the intricate network of ditches and rarest habitats on earth, covering just 22 hectares (53 acres). It waterways in this area of lowland grazing meadows that is home to supports around 35 nationally rare, scarce and threatened native two thirds of our native aquatic plant species, including Endangered plants. Highly fragmented and plagued by invasive scrub, this is greater water-parsnip Sium latifolium and Critically Endangered one of the top botanical Sites In sharp-leaved pondweed Potamogeton acutifolius. In areas of heavy Peril in the country. Evergreen oak infestation the invasive plants virtually eliminate all other plants. Quercus ilex, shrubby scorpion- This is particularly worrying as greater water-parsnip is already vetch Coronilla valentina subsp. one of the fastest declining plants in Britain and the fen raft spider glauca and Jerusalem sage Dolomedes plantarius Phlomis fruticosa are being © Ray Woods/Plantlife Ray © - one of several rare removed in a costly programme and Endangered in an attempt to save this unique invertebrates of the habitat (pictured).
area - relies on native Renals Trevor © plants for its nursery webs. Livestock can 5 Somerset Levels also suffer as invasive A number of invasive plants have been found, presumed dumped plants can make in the wild, in this area over the past few years. Most recently water appear as solid two plants considered by many to be possible invaders of the ground. future (they are already invasive in other, warmer countries), water A sheep struggles through invasive floating pennywort hyacinth Eichhornia crassipes and water lettuce Pistia stratiotes, were found growing along a 500m stretch of the King’s Sedgemoor Drain. The first record of water 2 Surrey Commons primrose Ludwigia was from here too. The area appears to be a hotspot for The invasive aquatic plants New Zealand pigmyweed Crassula illegal dumping of unwanted invasive helmsii, parrot’s-feather Myriophyllum aquaticum, and water fern plant matter in the wild, and invasive Azolla filliculoides have infested a number of ponds containing plants are now a significant threat
Critically Endangered starfruit Damasonium alisma, Vulnerable Agency Environment © to this internationally important brown galingale Cyperus fuscus, and Near Threatened pillwort Potentially invasive landscape. Pilularia globulifera - some of Britain’s rarest plants. Many sites water lettuce have now been dredged and chemically sprayed in an attempt to rid them of the invasive problem plants. 6 Lindisfarne The beautiful and internationally important sand dunes and mudflats of Lindisfarne are the only place on earth where the Endangered orchid Lindisfarne helleborine Epipactis sancta lives. For some years efforts have been underway to protect Lindisfarne from invasive pirri-pirri-bur Acaena novae-zelandiae, thought to have arrived here attached to wool imports. Removal techniques
© Tim Pankhurst/Plantlife Tim © tried to date include digging, pulling, smothering, applying herbicides, rotoburying, grazing, burning and even dragging a Invasive parrot’s-feather carpet (for the burs to stick to) behind a quad bike. As a much 3 West Clandon visited gem of the north east, tourists are unwittingly assisting After 60 years of dramatic population decline, the Endangered the plant to spread as the burs www.ukwildflowers.com © broad-leaved cudweed Filago pyramidata has become one of stick to shoes and clothing. So far, our rarest plants. It is now known from just eight sites in Britain, the invasive potential of this plant including West Clandon in Surrey. West Clandon is also plagued has not been recognised in law. Lindisfarne helleborine by invasive buddleia (butterfly-bush) Buddleja davidii. New management has been agreed to help keep the buddleia under control and give the cudweed a fighting chance. 7 South Buckinghamshire Commons Critically Endangered starfruit Damasonium alisma was restricted to just three native sites in Britain by 1990, following decades of decline. The remaining populations, now confined to south Buckinghamshire, are threatened by invasive New Zealand pigmyweed Crassula helmsii. Adverse weather conditions over the past few years have meant the limited seasonal window of © Bob Gibbons Bob ©
© Crown Copyright 2009. GBNNSS. 2009. Copyright Crown © opportunity to try and tackle the invasive plant has been missed. There is now probably only one site where starfruit is regularly found. Invasive buddleia Starfruit
HORIZON SCANNING FOR INVASIVE NON-NATIVE PLANTS 5 8 The Broads 12 Breamore Marsh Large stands of floating pennywort Hydrocotyle ranunculoides are Home to the rare brown galingale Cyperus fuscus, Breamore being tackled in the Norfolk and Suffolk Broads National Park in the Marsh (Hampshire) became one of the first and most botanically hope that it can be prevented from causing widespread damage important sites in the country to be plagued by non-native water across our largest protected wetland. Rapid response is the most primrose Ludwigia when it was discovered in summer 2009. In effective action once invasive plants are found at a site, but some France water primroses are causing huge problems. An eradication plants like New Zealand pigmyweed Crassula helmsii are extremely attempt against invasive Ludwigia is being made in Britain as so few difficult to control even sites are affected at the moment. Early intervention offers the most then. At Lound Lakes, realistic chance once home to pillwort of success once Pilularia globulifera, three an invasive plant lakes are now heavily Renals Trevor © has made it into
infested with invasive the wild. In spite Renals Trevor © pigmyweed. A recent of two chemical botanical survey found treatments the no pillwort whatsoever. Invasive New Zealand pigmyweed invasive plants are still flourishing at Breamore. Further 9 Lundy Island treatment at the Invasive species are often particularly damaging when they arrive site is planned. on islands where ecosystems have developed in isolation. The stakes Invasive water primrose can be high where endemic species have evolved, and Lundy Island in the Bristol Channel is no exception. The threat from rhododendron Rhododendron ponticum to the endemic Vulnerable Lundy cabbage 13 The Lizard Coincya wrightii and its associated endemic invertebrates is being Lizard Point is home to the endemic wild asparagus Asparagus managed by a officinalis subsp. prostrates (Endangered), long-headed clover rhododendron Trifolium incarnatum subsp. molinerii (Vulnerable) and prostrate eradication broom Cytisus scoparius subsp. maritimus (Near Threatened). programme. All are now threatened by the invasive hottentot-fig Carpobrotus edulis and three-cornered garlic Allium triquetrum, although areas of the cliffs are being cleared of the invasive plants. The area is Invasive rhododendron Long/Plantlife Deborah © also home to the chough Pyrrhocorax pyrrhocorax – a bird 10 Bala Lake/Llyn Tegid trying to make a Wales is the UK’s stronghold for the rare floating water-plantain comeback in England. Luronium natans, a UK BAP priority species which occurs in Bala Choughs need areas PLC Group RPS © Lake. Although not yet also present, New Zealand pigmyweed of bare ground, so Crassula helmsii is found in a private pond upstream of the lake. ground-smothering The owner of the Hottentot-fig could pond is reluctant to pose a threat to control the spread of their recolonisation the pigmyweed and progress if it is not it therefore presents a managed. real and uncontainable Invasive Hottentot-fig
risk to the health of Gagg/Plantlife Andrew © this important habitat and its rare flora. Floating water-plantain 14 Avon Gorge With its unique assemblage of threatened calcareous plants, 11 Lough Corrib including rarities such as honewort Trinia glauca, Vulnerable Invasive curly waterweed Lagarosiphon major has taken over Bristol rock-cress Arabis scabra, hutchinsia Hornungia petraea, large sections of Lough Corrib, Ireland’s second largest lake. Vulnerable round-headed leek Allium sphaerocephalon and Near Lough Corrib is of significant conservation importance. However, Threatened dwarf mouse-ear where once there were meadows of stoneworts (plants that are Cerastium pumilum, Avon indicators of a healthy freshwater system), now there is just curly Gorge has a lot to lose from waterweed. Prior to the invasion, Lough Corrib supported one of the the presence of non-native most extensive stonewort beds in Ireland. Amongst the techniques invasive evergreen oak trialled to remove the invasive plant is the use of black geotextiles Quercus ilex, cotoneasters © Andrew Gagg/Plantlife Andrew © which block out light and suppress plant growth. Curly waterweed Cotoneaster microphyllus is widely sold (often labelled agg. and laurustinus ‘pond oxygenator’ or by the Viburnum tinus. Recent work incorrect Latin name Elodea has done much to free areas crispa) and is almost ubiquitous of these invaders, but the in garden ponds. As such, it is inaccessibility of many sites almost inevitable that more and makes work difficult and © Su Cooper/Plantlife Su © more freshwater habitats will be costly. affected by this invasive plant. Invasive curly waterweed Round-headed leek 6 HERE TODAY, HERE TOMORROW? 15 Portland 18 Great Orme Portland demonstrates how much lower plant interest is at stake Several non-native cotoneasters - mainly Cotoneaster horizontalis, due to invasive non-native plants. It is one of the richest coastal C. integrifolius, C. conspicuus and C. sternianus - along with limestone sites for lichens in the whole of the British Isles with strawberry-tree Arbutus unedo, Turkey oak Quercus cerris and over 220 species recorded, of which four are found nowhere else in evergreen oak Quercus ilex are invading areas of this internationally Britain and 11 are Red Listed. Its bryophyte flora is also extensive important limestone headland where nationally and locally with 137 species including five Red List species. The nationally threatened native plants occur. Native plants that are threatened rare and Vulnerable liverwort blackwort Southbya nigrella is at the include wild cotoneaster Cotoneaster cambricus, goldilocks aster northern edge of its range in southern Britain. Portland supports Aster linosyris, spotted cat’s-ear Hypochaeris maculata, dwarf 90% of the UK population mouse-ear Cerastium of blackwort but it is pumilum, Nottingham directly threatened by catchfly Silene nutans, invasive non-native hairy-fruited cornsalad cotoneaster which is now Valerianella eriocarpa, © Bryan Edwards Bryan © established at Portland and dark-red helleborine
and appears to be Gagg/Plantlife Andrew © Epipactis atrorubens. In spreading. Invasive non- several sites Nottingham native buddleia Buddleja catchfly has been davidii has also become completely eradicated established here. by invading red valerian Dark red helleborine Centranthus ruber. Blackwort 19 Lake District 16 Atlantic Woodlands Several invasive non-native plants are already affecting the Lake Many lower plants and fungi – arguably Britain’s most important District National Park. New Zealand pigmyweed Crassula helmsii is contribution to global biodiversity – are particularly at risk from found in a number of the waterbodies, including Coniston, Grasmere invasive non-native plants. Rhododendron Rhododendron ponticum and Windermere. Grasmere’s fragile reedbeds are also being taken can cause severe impoverishment of bryophytes and lichens. over by American skunk-cabbage Lysichiton americanus. High Declines in bryophyte and lichen diversity in Scotland’s Atlantic visitor numbers, especially by those using the lakes for water Woodlands where rhododendron has formed dense cover have activities and recreation, means that accidental spread of aquatic been observed. Some ravines infested with rhododendron have invasive plants is highly likely. A new strategic approach to tackling completely lost their riparian bryophyte communities. Without invasive species is now being co-ordinated across the whole of better management Cumbria in an effort to maximise the impact of limited resources. A of rhododendron in our strategic approach to dealing with affected sites and invasive plant Atlantic woodlands threats is desperately needed at a national level too. some of the best moss and liverwort
© Gordon Rothero Gordon © communities in Europe may be lost. Twenty four top botanical sites in the Atlantic Woodland Important
Plant Area that are Nottingham/Plantlife Sue © being damaged by rhododendron have been identified. Lake District National Park
Atlantic woodland 20 Ranscombe Farm The calcareous woodland at Ranscombe boasts an impressive 17 Lydstep Head diversity of woodland ground flora, including the Endangered lady Populations of the Vulnerable liverwort green blackwort Southbya orchid Orchis purpurea, Endangered tophacea at Lydstep Head in the Pembrokeshire National man orchid Orchis anthropophora Park have declined following encroachment by small-leaved and Vulnerable fly orchid Ophrys cotoneasters Cotoneaster insectifera. Yet efforts to open up the
microphyllus agg. The woodland canopy to restore calcareous Gagg/Plantlife Andrew © liverwort is now restricted wood pasture – a rare habitat on chalk to a single very narrow – are being thwarted by sycamore path on the site and Acer pseudoplatanus which seeds into removal of cotoneaster any opening that is created. Although is required to prevent sycamore was introduced here in the shading of the remaining 16th century, is now spread across
© Crown Copyright 2009. GBNNSS. 2009. Copyright Crown © colonies. Only a handful Britain, and is often accepted as ‘part of sites in the UK support of the furniture’, its presence is still the liverwort. problematical in some of the country’s top botanical hotspots. Invasive cotoneaster Man orchid HORIZON SCANNING FOR INVASIVE NON-NATIVE PLANTS 7 Horizon scanning: preventing invasion new by problem plants The most cost effective and least environmentally damaging approach to solving the problems caused by non-native invasive plants is by preventing them from escaping into the wild in the first place. This may require potentially non-native invasive plants to be banned from sale, prohibited from being planted in the wild, or eradicated from known sites in the wild.
Although the damage caused by Plantlife devised a ‘Rapid Risk invasive non-native plants is real and Assessment’ screening process for burgeoning, problem plants represent quickly assigning a broad level of a small sub-set of the 70,000 or so invasive threat to a non-native plant. non-native plants available to buy We applied the process to almost 600 in Britain. The majority of these plants that are grown or sold here or are non-native plants are unlikely to already present but not yet widespread cause environmental damage now in the wild. The system is based on the or in future, and we don’t want to Australian Weed Risk Assessment*, a unnecessarily curb trade or the process that has been well-received enjoyment of plants by gardeners and internationally as a tool for identifying pond-keepers. But the impact that the invasive threats. few highly invasive non-native plants have on sites throughout Britain is not By recommending a shortlist of plants cancelled out by the minimal impact for which the more detailed risk of the majority. So how can we hope to assessment is considered imperative differentiate between plants we should and/or prudent and a list of plants for worry about and those which are which such assessment is deemed unlikely to ever be of concern? currently unnecessary, the Rapid Risk Assessment screening process can The current mechanism used to try to help policy-makers to prioritise limited identify potential invasive plants of resources. Given the rapid nature of the the future in Britain involves a time- screening process, plants identified consuming detailed risk assessment as potentially invasive do not warrant process. This makes it inappropriate to trade or planting restrictions based on apply to large numbers of plants. this assessment alone.
* Pheloung, P.C. (1995) Determining the weed potential of new plant introductions to Australia. Australian Weeds Committee Commissioned Report & Pheloung, P.C., Williams, P.A., & Halloy, S.R. (1999) A weed risk assessment model for use as a biosecurity tool evaluating plant introductions. Journal of Environmental Management. 57(4): 239-251.
8 HERE TODAY, HERE TOMORROW? Rapid Risk Assessment screening questions
Question Maximum score Q1. What is its rate of spread in the UK? 4 Q2. To what climate is the plant suited? 3 Q3. Is it an environmental weed in natural and valued habitats/designated sites? 4 Q4. Has the plant become naturalised where grown (globally)? 2 Q5. Does the plant have a history of repeated cultivation (and associated introductions) in the UK? 2 Q6. Is the plant naturalised beyond its native range? 2 Q7. Is it a congeneric weed? 2 Q8. Is it unpalatable to grazing animals (including for reasons of toxicity/spines/thorns)? 1 Q9. Can it tolerate a wide range of soil conditions (within the aquatic or terrestrial system)? 1 Q10. Does it have a climbing or smothering growth habit, and/or form dense thickets? 4 Q11. Does/can it produce viable seed in the UK? 1 Q12. Does/can it reproduce by vegetative fragmentation? 2 Q13. What is its minimum generative time (years)? 1 Q14. Are propagules (likely to be) dispersed unintentionally (plants growing in heavily trafficked areas)? 1 Q15. Are propagules (likely to be) dispersed intentionally by people? 1 Q16. Are propagules (likely to be) dispersed as a produce contaminant? 1 Q17. Are propagules adapted to wind dispersal? 1 Q18. Are propagules water dispersed? 1 Q19. Are propagules bird/other animal dispersed? 1 Q20. Does the plant have prolific seed production? 1 Q21. Is there evidence that a persistent propagule bank is formed (at least 1 year)? 1 Q22. Does it tolerate or benefit from mutilation/cultivation/herbicides? 1
Of the 599 non-native freshwater and terrestrial plants that have already been assessed by Plantlife and the Freshwater Biological Association (under a contract from Plantlife): 92 are given a 5-star ‘Critical’ ranking: Plantlife recommends as a matter of priority that they are subject to the more detailed risk assessment, as commissioned by the GB Non-Native Species Secretariat; 55 are ranked ‘Urgent’ (4 star): Plantlife highly recommends they are subject to the more detailed risk assessment; 72 are ranked ‘Moderate Risk’ (3 star): Plantlife recommends they are subject to the more detailed risk assessment; and 380 are ranked ‘Low Risk’ (1 star): no further assessment is considered necessary at present. Ranks assigned to each plant are listed on pages 13-18.
Information about the selection of plants included in The Rapid Risk Assessments make no consideration as this study, as well as a more comprehensive analysis to the volumes of specific plants in the horticultural of its findings, can be found in our detailed report and aquatics trades. As the likelihood of introduction Horizon scanning for invasive non-native plants in and establishment in the wild will probably be greater Great Britain, produced for and published by Natural for plants that are most widely sold compared to those England. Copies of this report can be downloaded from with low volumes of trade, such information should www.plantlife.org.uk and www.naturalengland.org.uk be taken into account when more comprehensive risk or are available upon request. assessments are conducted.
HORIZON SCANNING FOR INVASIVE NON-NATIVE PLANTS 9 Ones
to Plantlife believes these plants are on the brink of becoming invasive in Britain, watch but they have been overlooked in recent legislative changes that aimed to provide better protection for the environment from invasive species.
© RPS Group PLC Group RPS © © Kristian Peters Peters Kristian ©
© Crown Copyright 2009. GBNNSS. 2009. Copyright Crown ©
False-acacia Robinia pseudoacacia False-acacia is extensively planted in Britain and Large-flowered waterweed spreads mainly by suckering. Egeria densa Himalayan knotweed
© Crown Copyright 2009. GBNNSS. 2009. Copyright Crown © Although it is currently This submerged aquatic uncommon in the wild it Persicaria wallichii plant is very popular in the is showing alarming signs This plant has been grown freshwater aquarium trade. of spreading in disturbed, in cultivation but is less Plants are often discarded ruderal habitats (for example popular today than in the into the wild once they on railway lines). Its rapid past. It is still present in out-grow their tanks. It spread, suckering nature, some gardens and is still seems introductions as a spiny, impenetrable habit available commercially result of dumping in the Evergreen oak (holm oak) when established, and its from some nurseries. As wild are continuing, and Quercus ilex ability to regrow when cut with similar plants (like there is great fear that if our An evergreen tree used in down mean that it is a major Japanese knotweed Fallopia climate warms even slightly, parks, churchyards and large cause for concern. In France japonica), this large plant, the plant will ‘take off’, gardens, evergreen / holm and Italy the tree is freely reaching up to 2m tall, outcompete native plants oak is now regenerating establishing in woodlands, becomes established on and clog up waterways freely in parts of south and much as sycamore has done stream sides, hedge banks, and drainage systems. east England. It has become here. We have the ability woodland edges, roadsides, Large-flowered waterweed established in a range of key to control it in the wild in railway banks and waste flowers only in warm water botanical sites particularly Britain at the moment, ground. There it grows into conditions – it was seen in on dry limestone and chalk but it is likely to become a extremely dense stands flower for the first time in sites in coastal Britain. It has major established pest in the that out-compete all native Surrey in 2006, having been also achieved more localised coming decades. vegetation. recorded in the wild since establishment within 1950. Conservationists in heathland areas. Cornwall are now dealing with infestations of the plant in the wild. HORIZON SCANNING FOR INVASIVE NON-NATIVE PLANTS 10 ‘Critical’ ranking: Plantlife recommends they are subject to the more detailed risk assessment as a matter of priority ‘Urgent’: Plantlife highly recommends they are subject to the more detailed risk assessment
© RPS Group PLC Group RPS © © RPS Group PLC Group RPS © © RPS Group PLC Group RPS ©
Tree of heaven
Pickerelweed GBNNSS. 2009. Copyright Crown © Ailanthus altissima Pontederia cordata This deciduous tree, This plant is extremely originally from China, is popular in water gardens very widely planted – in where it is grown as a gardens, streets, parks and submerged or marginal plant public spaces. As well as in pools and ponds or as a getting into the wild by bog plant. It is very widely seed dispersal from growing Turkey oak available to buy. These large, Pirri-pirri-bur trees, it is also spread by the Quercus cerris vigorous plants grow up to Acaena novae-zelandiae dumping of excess material. 1m tall and often out-grow Turkey oak is a deciduous Like rhododendron, this their space in garden pools Originating from Australia tree that has been planted plant prevents other and ponds; they are then and New Zealand, this plant in woodlands, estates, vegetation from growing sometimes discarded into is spreading in Britain and large gardens, in parks and in the surrounding area by the wild. It is likely that some has become established at along roads. It has now releasing toxic compounds. populations also arise by many important wildlife naturalised and is spreading Attempts to control it by deliberate planting in the sites. Introduction is mainly into calcareous grassland cutting result in more wild – for example by anglers through the dumping of and heathland. It has vigorous growth. It is not wanting to ‘improve’ fishing garden material in the wild. been recorded from a large yet known to be causing ponds (no doubt without From there its hooked burs number of important nature problems at sites of realising the problems the mean it is easily spread by conservation sites. Although botanical interest here, but plants may cause). sheep and other animals. It many of these reports are of becomes especially invasive in some countries where it small numbers of the tree at when it establishes on cool, has already caused many the moment, Turkey oak will damp cliffs and upland problems, it is called the undoubtedly continue to habitats – often the very ‘tree of hell’. colonise open grassland and types of site where threatened heathland areas, becoming native plants occur. a major nuisance in years to come.
11 HERE TODAY, HERE TOMORROW? Recommendations:
1. All 5*, 4* and 3* plants should be subject to a comprehensive risk assessment, as commissioned by the GB Non-Native Species Secretariat, without delay; 2. Any additional freshwater non-native plant and all marine plants found to be traded in Britain should be subject to the Rapid Risk Assessment, as should all produce contaminants (‘hitchhikers’); 3. All plants screened should be reviewed periodically to take account of emerging evidence and information, changes in climate, and new horticultural varieties that become available as these may be hardier than the plant varieties screened here; 4. Any development of this scheme should give greater consideration to the weighting of questions and the handling of uncertainty (see the full report for more details); 5. A simple checklist should be devised, potentially based on the Rapid Risk Assessment questions, to help horticultural traders make more informed decisions over the sourcing and growing of non-native plant commodities.
Limitations of the screening process
Predicting plant invasiveness cannot be done with complete accuracy: there will always remain the risks of declaring a plant to be low risk which then goes on to become invasive (a ‘false negative’ result), or declaring a plant to be higher risk when it does not become invasive (a ‘false positive’ result).
This Rapid Risk Assessment process provides a horizon scanning service which can be used to help prioritise resources by recommending a shortlist of plants for which more detailed assessment is considered imperative and/or prudent. Due to its rapid nature, it cannot be used to ‘blacklist’ traded plants before further research is undertaken. To reduce the risk of false negative results, a precautionary principle was applied which errs on the side of caution. This will increase the likelihood of false positive results.
12 HERE TODAY, HERE TOMORROW? Rapid Risk Assessment ranking
Latin name* Common name Star rating Latin name* Common name Star rating Abies grandis Giant fir Anubias barteri Abies procera Noble fir Anubias caladiifolia Acaena novae-zelandiae Pirri-pirri-bur Anubias callos Acer cappadocicum Cappadocian maple Anubias coffeefolia Acer saccharinum Silver maple Anubias congensis Acorus calamus Sweet flag Anubias gigantea Acorus gramineus Slender sweet flag Anubias gracilis Acorus gramineus 'Pusillus' Miniature sweet flag Anubias hastifolia Aesculus carnea Red horse chestnut Anubias heterophylla Aesculus indica Indian horse chestnut Anubias lanceolata Ailanthus altissima Tree-of-heaven Anubias nana Dwarf anubias Alchemilla mollis Garden lady's-mantle Aponogeton capuronii Corkscrew lace plant Alisma parviflora American water-plantain Aponogeton crispus Allium subhirsutum Hairy garlic Aponogeton distachyos Cape-pondweed Allium triquetrum Three-cornered garlic Aponogeton elongatus Alnus cordata Italian alder Aponogeton fenestralis Alocasia x amazonica Amazon lily Aponogeton henkelianus Narrow-leaved lace plant Alocasia cucullata Chinese taro Aponogeton krauseanus Alocasia odora Upright elephants ears Aponogeton longiplumulosus Alocasia plumbea Elephant ear Aponogeton madagascarensis Alpinia zerumbet 'Variegata' Pink porcelain lily Aponogeton natans Alstroemeria aurea Peruvian lily Aponogeton rigidifolius Alternanthera reineckii Aponogeton siamensis Alternanthera sessilis Sessile joyweed Aponogeton ulvaceus Alternanthera 'Sunset' Aponogeton undulatus Alternanthera tenella Araucaria araucana Monkey-puzzle Alyssum saxatile Golden Alison Aruncus dioicus Buck's-beard Amaranthus bouchonii Indehiscent amaranth Arundo donax Giant reed Amaranthus hybridus Green amaranth Aucuba japonica Spotted-laurel Ambrosia artemisiifolia Ragweed Azolla caroliniana Carolina mosquito fern Ambulia aromatica Azolla filiculoides Water fern Ammania gracilis Large ammania Bacopa caroliniana Giant babies tears Ammania senegalensis Bacopa lanigera Ampelodesmos pliniana Bacopa monnieri Coastal water hyacinth Amsonia hubrichtii Hubrischt's bluestar Bacopa myriophylloides Fine-leaved water-hyssop Amsonia orientalis Eastern bluestar Bacopa rotundifolia Disk water-hyssop Amsonia tabernaemontana Eastern bluestar Barclaya longifolia Orchid lily Anemone blanda Balkan anemone Bassia scoparia Summer-cypress Anemopsis californica Yerba mansa Baumea rubiginosa Soft twig Anthemis punctata Sicilian chamomile Berberis darwinii x empetrifolia Darwin's barberry Anubias afzelii Berberis gagnepainii Gagnepain's barberry Anubias angustifolia Berberis julianae Chinese barberry
‘Critical’ ranking: Plantlife recommends they are subject to the more detailed risk assessment as a matter of priority ‘Urgent’: Plantlife highly recommends they are subject to the more detailed risk assessment ‘Moderate Risk’: Plantlife recommends they are subject to the more detailed risk assessment ‘Low Risk’: no further assessment is considered necessary at present
* In some cases the name listed is a trade name / name under which a plant is sold rather than a fully-recognised botanical name.
HORIZON SCANNING FOR INVASIVE NON-NATIVE PLANTS 13 Latin name* Common name Star rating Latin name* Common name Star rating Berberis thunbergii Thunberg's barberry Cotoneaster conspicuus x Tibetan cotoneaster C. x dammeri suecicus Bergenia crassifolia Elephant-ears Cotoneaster dammeri Bearberry cotoneaster Beta vulgaris subsp. cicla Root beet Cotoneaster dielsianus Diels' cotoneaster Bidens connata London bur-marigold Cotoneaster divaricatus Spreading cotoneaster Blyxa aubertii Bamboo plant Cotoneaster franchetii Franchet's cotoneaster Blyxa japonica Cotoneaster frigidus x salicifolius Tree cotoneaster Bolbitis heteroclita El nino fern Cotoneaster hjelmqvistii Hjelmqvist's cotoneaster Bolbitis heudelotii Cotoneaster horizontalis Wall cotoneaster Brachyglottis monroi Monro's ragwort Cotoneaster lacteus Late cotoneaster Brachyglottis 'Sunshine' Hedge ragwort Cotoneaster microphyllus agg. Small-leaved cotoneasters Brunnera macrophylla Great forget-me-not Cotoneaster obtusus Dartford cotoneaster Buddleja davidii Butterfly-bush Cotoneaster prostratus Procumbent cotoneaster Buddleja davidii x globosa Butterfly-bush (B. x weyeriana) Cotoneaster rehderi Bullate cotoneaster Buddleja globosa Orange-ball-tree Cotoneaster salicifolius Willow-leaved cotoneaster Cabomba aquatica Fanwort Cotoneaster simonsii Himalayan cotoneaster Cabomba caroliniana Carolina water-shield Cotoneaster sternianus Stern's cotoneaster Cabomba furcata Red Cabomba Cotula coronopifolia Buttonweed Calla palustris Bog arum Crassula helmsii New Zealand pigmyweed Caltha introloba Alpine marsh-marigold Crinum calamistratum Caltha leptosepala White marsh-marigold Crinum erubescens Swamp lily Caltha natans Floating marsh-marigold Crinum natans Caltha palustris Giant kingcup Crinum thaianum subsp. polypetala Crocosmia paniculata Aunt-Eliza Caltha palustris var. barthei Crocosmia pottsii Pott's montbretia Caltha palustris var. radicans Crocosmia x crocosmiiflora Montbretia Caltha sagittata Crocus chrysanthus Golden crocus Campanula portenschlagiana Adria bellflower Crocus speciosus Bieberstein's crocus Campanula poscharskyana Trailing bellflower Crocus tommasinianus Early crocus Canna tuerckheimii Crocus vernus Spring crocus Cardamine corymbosa New Zealand bitter-cress Cryptocoryne affinis Cardamine lyrata Chinese ivy Cryptocoryne albida Cardamine macrophylla Large-leaved cuckooflower Cryptocoryne aponogetifolia Cardamine raphanifolia Greater cuckooflower Cryptocoryne balansae Carex muskingumensis Musk sedge Cryptocoryne beckettii Ceratochloa carinata California brome Cryptocoryne bullosa Ceratopteris cornuta Cryptocoryne ciliata Ceratopteris thalictroides Sumatra fern Cryptocoryne cordata Chamaecyparis lawsoniana Lawson's cypress Cryptocoryne cordata var. Chamaecyparis nootkatensis Nootka cypress cordata 'Blassii' Chionodoxa forbesii Glory-of-the-snow Cryptocoryne crispatula var. tonkinensis Chionodoxa sardensis Lesser glory-of-the-snow Cryptocoryne crispulata var. Chladophora aegagrophila Marimbo balansae Chlorophytum bechettii Cryptocoryne griffithii Chlorophytum 'Pongol Sword' Cryptocoryne griffithii x C. cordata var.cordata Conyza sumatrensis Guernsey fleabane Cryptocoryne hudoroi Cordyline australis Cabbage-palm Cryptocoryne lingua Cornus alba White dogwood Cryptocoryne longicauda Cornus mas Cornelian-cherry Cryptocoryne minima Cortaderia richardii Early pampas-grass Cryptocoryne moehlmannii Cortaderia selloana Pampas-grass Cryptocoryne nurii Corydalis cheilanthifolia Fern-leaved corydalis Cryptocoryne parva Cotoneaster atropurpureus Purple-flowered cotoneaster Cryptocoryne pontederiifolia Cotoneaster bullatus Hollyberry cotoneaster Cryptocoryne pygmaea Cotoneaster conspicuus Tibetan cotoneaster 14 HERE TODAY, HERE TOMORROW? Latin name* Common name Star rating Latin name* Common name Star rating Cryptocoryne retrospiralis Echinodorus ozelot Cryptocoryne scurillis Echinodorus paniculatus Cryptocoryne striolata Echinodorus parviflorus Cryptocoryne thwaitesii Echinodorus quadricostata Chain sword Cryptocoryne undulata Echinodorus 'Red Flame' Cryptocoryne usteriana Echinodorus 'Red Rubin' Cryptocoryne walkerii Echinodorus 'Red Vein' Cryptocoryne wendtii Echinodorus 'Rose' Indian red sword Cryptocoryne x willisii Dainty water-chalice Echinodorus scaber Cryptomeria japonica Japanese red-cedar Echinodorus schlueteri Cupressus macrocarpa Monterey cypress Echinodorus schlueteri ‘Leopard’ Cyclamen coum Eastern sowbread Echinodorus tenellus Pygmy chain sword Cyclamen hederifolium Sowbread Echinodorus tricolor Cymbalaria pallida Italian toadflax Echinodorus uruguayensis Cyperus albostriatus 'Variegatus' Echinodorus uruguayensis x E. portoalegrensis Cyperus alternifolius Umbrella plant Echinodorus x barthii Cyperus eragrostis Pale galingale Echinops exaltatus Globe-thistle Cyperus haspan Echium pininana Giant viper's-bugloss Cyperus helferi Egeria densa Large-flowered waterweed Cyperus involucratus Umbrella plant Eichhornia azurea Cyperus papyrus Papyrus Eichhornia crassipes Water hyacinth Cyperus prolifer Dwarf papyrus Eichhornia diversifolia Cyperus rotundus Purple nut sedge Eleocharis dulcis variegated Chinese water-chestnut Cytisus striatus Hairy-fruited broom Eleocharis vivipara Umbrella hairgrass Darmera peltata Indian-rhubarb Elodea callitrichoides South American waterweed Deutzia scabra Deutzia Elodea canadensis Canadian waterweed Didiplis diandra Water hedge Elodea nuttallii Nuttall's waterweed Disphyma crassifolium Purple dewplant Equisetum camtschatcense Himalayan horsetail Dulichium arundinaceum Common three-way sedge Equisetum hyemale robustum Echinochloa crus-galli Cockspur Equisetum hyemale var. affine Echinodorus amazonicus Amazon sword Equisetum japonicum Echinodorus andreuxii Equisetum ramosissimum var. Branched horsetail Echinodorus argentinensis japonicum Echinodorus berteroi Upright burhead Equisetum scirpoides Dwarf horsetail Echinodorus bleheri Amazon sword Erigeron glaucus Seaside daisy Echinodorus bolivianus Bolivian sword plant Erigeron karvinskianus Mexican fleabane Echinodorus chrileni Eriocaulon cinereum Ashy pipewort Echinodorus compacta Eriocaulon 'Guangzhou' Echinodorus cordifolius Creeping burhead Eriocaulon setaceum Pipewort Echinodorus grisebachii Euphorbia amygdaloides subsp.robbiae Echinodorus harbich Euphorbia characias Mediterranean spurge Echinodorus harbii Eusteralis stellata Echinodorus horemanii Fallopia baldschuanica Russian-vine Echinodorus horizontalis Fallopia japonica x sachalinensis Hybrid Japanese knotweed Echinodorus ‘Imperial’ Fatsia japonica Fatsia Echinodorus ‘Ipica’ Forsythia suspensa x viridissima Forsythia Echinodorus ‘Kleiner Bar’ Galanthus caucasicus Caucasian snowdrop Echinodorus latifolius Galanthus elwesii Greater snowdrop Echinodorus magdalensis Galanthus ikariae Green snowdrop Echinodorus ‘Marble Queen’ Galanthus plicatus Pleated snowdrop Echinodorus martii (E. major) Gaultheria mucronata Prickly heath Echinodorus midi fleur Genista hispanica Spanish gorse Echinodorus mitchii Geranium endressii x versicolor French crane's-bill Echinodorus ‘Oriental’ HORIZON SCANNING FOR INVASIVE NON-NATIVE PLANTS 15 Latin name* Common name Star rating Latin name* Common name Star rating Geranium ibericum x Caucasian crane's-bill Iris orientalis Turkish iris platypetalum Isoetes japonica Geranium macrorrhizum Rock crane's-bill Isoetes velata Glossostigma diandrum Juncus 'Curly Gold Strike' Glossostigma elatinoides Juncus decipiens 'Curly-wurly' Gratiola officinalis Hedge hyssop Juncus ensifolius Swordleaf rush Griselinia littoralis New Zealand broadleaf Juncus 'Goldstrike' Gunnera tinctoria Giant-rhubarb Juncus repens Lesser creeping rush Gymnocoronis spilanthoides Senegal tea plant Juncus xiphioides Iris-leaved rush Hebe brachysiphon Hooker's hebe Kerria japonica Kerria Hebe dieffenbachii Dieffenbach's hebe Kniphofia uvaria Red-hot-poker Hedera colchica Persian ivy Kniphofia x praecox Greater red-hot-poker Helianthus annuus Sunflower Lagarosiphon major Curly waterweed Helleborus argutifolius Corsican hellebore Lagarosiphon muscoides Helleborus orientalis Lenten-rose Lagenandra ovata Malayan sword Hemianthus callitrichoides Pearl grass Lagenandra thwaitesii Hemianthus micranthemoides Nuttalls' mudflower Lamiastrum galeobdolon subsp. Variegated yellow archangel Hemigraphis colorata Purple waffle argentatum Hemigraphis exotica Laurus nobilis Bay Heteranthera bettzinckiana Lavandula angustifolia x latifolia Garden lavender Heteranthera dubia Buffalo grass Lemna minuta Least duckweed Heteranthera zosterifolia Stargrass Ligustrum ovalifolium Garden privet Heuchera sanguinea Coralbells Lilaeopsis brasiliensis Brazilian microsword Holodiscus discolor Oceanspray Lilaeopsis mauritiana Hottonia inflata Featherfoil Lilaeopsis novae-zelandiae Houttuynia cordata Lizard tail Limnobium laevigatum Amazon frogbit Hyacinthoides hispanica x Spanish bluebell Limnobium spongia American spongeplant non-scripta Limnophila aquatica Red temple Hyacinthus orientalis Hyacinth Limnophila aromatica Giant ambulia Hydrangea macrophylla Hydrangea Limnophila conferta Hydrocleys nymphoides Water poppy Limnophila gigantea Hydrocotyle leucocephala Brazilian pennywort Limnophila heterophylla Hydrocotyle novae-zelandiae New Zealand pennywort Limnophila hippuroides Hydrocotyle ranunculoides Floating pennywort Limnophila sessiliflora Asian ambulia Hydrocotyle sibthorpioides Lawn marsh-pennywort Lindernia grandiflora Blue moneywort Hydrocotyle variegata Lindernia rotundiflora Hydrocotyle verticillata Whorled marsh-pennywort Lobelia erinus Garden lobelia Hydrotriche hottoniiflora Lonicera caprifolium x etrusca Perfoliate honeysuckle Hygrophila angustifolia Willow hygro Lonicera involucrata Californian honeysuckle Hygrophila corymbosa Starhorn Lonicera japonica Japanese honeysuckle Hygrophila costata Lonicera nitida Wilson's honeysuckle Hygrophila difformis Water wisteria Lonicera pileata Box-leaved honeysuckle Hygrophila lacustris Gulf swampweed Ludwigia arcuata Hygrophila polysperma Ludwigia brevipes Long beach primrose Hygrophila rosae australis Ludwigia glandulosa Hygrophila rosanervis Ludwigia grandiflora Water primrose Hygrophila salicifolia Ludwigia helminthorrhiza Hygrophila thailand stricta Ludwigia inclinata Hygroryza aristata Ludwigia inclinata verticillata Hypericum forrestii Forrest's tutsan 'Pantanale' Iberis sempervirens Perennial candytuft Ludwigia latifolia Ilex aquifolium x perado Highclere holly Ludwigia ovalis Iris ensata Japanese iris Ludwigia peploides Floating primrose willow Iris laevigata Japanese water iris Ludwigia perennis
16 HERE TODAY, HERE TOMORROW? Latin name* Common name Star rating Latin name* Common name Star rating Ludwigia repens Creeping primrose willow Oenanthe javanica 'Flamingo' Ludwigia x kentiana Hampshire-purslane Olearia macrodonta New Zealand holly Lupinus arboreus Tree lupin Orontium aquaticum Golden club Lupinus arboreus x polyphyllus Tree lupin (L. x regalis) Ottelia ulvifolia Lysichiton americanus American skunk-cabbage Oxalis exilis Least yellow-sorrel Lysichiton camtschatcensis Asian skunk-cabbage Oxalis latifolia Garden pink-sorrel Lythrum virgatum Purple loosestrife 'Dropmore Paeonia officinalis Garden peony 'Dropmore Purple' Purple' Papaver atlanticum Atlas poppy Marsilea crenata Parthenocissus inserta False Virginia-creeper Marsilea quadrifolia European water clover Parthenocissus quinquefolia Virginia-creeper Marsilea hirsuta Rough water clover Paulownia tomentosa Foxglove-tree Mayaca fluviatilis Green mayaca Peltandra sagittifolia Spoonflower Mayaca sellowiana Peltandra virginica Green arrow arum Mayaca vandelli Persicaria campanulata Lesser knotweed Mentha cervina Hart's pennyroyal Persicaria wallichii Himalayan knotweed Micranthemum umbrosum Shade mudflower Petasites japonicus Giant butterbur Microsorum latifolius Petunia axillaris x integrifolia Petunia Microsorum pteropus Java fern Phacelia tanacetifolia Phacelia Mimulus cupreus x guttatus Scarlet monkeyflower Phalaris paradoxa Awned canary-grass Monochoria hastata Philadelphus coronarius Mock-orange Monosolenium tenerum Philadelphus x virginalis Hairy mock-orange Morus nigra Black mulberry Photinia davidiana Stranvaesia Myriophyllum aquaticum Parrot's-feather Phyllanthus fluitans Red root floater Myriophyllum elatinoides New Zealand water-milfoil Physalis peruviana Cape-gooseberry Myriophyllum hippuroides Western milfoil Picea sitchensis Sitka spruce Myriophyllum matogrossense Pinus contorta Lodgepole pine Myriophyllum pinnatum Pinus nigra Austrian pine, Corsican pine Myriophyllum propinquum Pinus strobus Weymouth pine Myriophyllum propium Pistia stratiotes Water lettuce Myriophyllum 'Red Stem' Pittosporum tenuifolium Kohuhu Myriophyllum tuberculatum Platanus x hispanica Oriental plane Nelumbo nucifera Indian lotus Pogostemon helferi Neobeckia aquatica Lake cress Polypogon viridis Water bent Nesaea crassicaulis Pontederia cordata Pickerelweed Nicandra physalodes Apple-of-Peru Pontederia lanceolata Nicotiana alata x forgetiana Sweet tobacco Populus trichocarpa Western balsam-poplar Nicotiana forgetiana Red tobacco Proserpinaca palustris Mermaid weed Nigella damascena Love-in-a-mist Prunus lusitanica Portugal laurel Nomaphila siamensis Prunus serrulata Japanese cherry Nomaphila stricta Pseudofumaria alba Pale corydalis Nomaphila variegata Pseudosasa japonica Arrow bamboo Nothofagus nervosa Dombey's beech Pterocarya fraxinifolia Caucasian wingnut Nothofagus obliqua Roble Pyracantha coccinea Firethorn Nuphar advena Beaver lily Pyracantha rogersiana Asian firethorn Nuphar japonicum Quercus cerris Turkey oak Nymphaea mexicana Banana water lily Quercus cerris x suber Turkey oak (Q. x crenata) Nymphaea odorata Fragrant water lily Quercus ilex Evergreen oak Nymphaea odorata subsp. tuberosa Quercus rubra Red oak Nymphaea odorata var. minor Lesser fragrant water lily Ranunculus limosella Mud buttercup Nymphaea pubescens Purple water Lily Rheum x hybridum Rhubarb Nymphaea tetragona Pigmy water lily Rhododendron luteum Yellow azalea Nymphaea zenkeri Red tiger lotus Rhododendron ponticum x R. Rhododendron hybrid maximum Nymphoides aquatica Banana plant Rhus typhina Stag's-horn sumach
HORIZON SCANNING FOR INVASIVE NON-NATIVE PLANTS 17 Latin name* Common name Star rating Latin name* Common name Star rating Rhynchospora colorata Star sedge Spiraea cantoniensis x trilobata Himalayan spiraea Ribes odoratum Buffalo currant Spiraea douglasii x salicifolia Lange's spiraea Robinia pseudoacacia False-acacia Stachys byzantina Lamb's-ear Rosa ferruginea Red-leaved rose Stenotaphrum secundatum St. Augustine grass variegatum Rosa 'Hollandica' Dutch rose Symphoricarpos microphyllus x Snowberry Rosa multiflora Many-flowered rose orbicularis Rosa rugosa Japanese rose Symphytum 'Hidcote Blue' Creeping comfrey Rosmarinus officinalis Rosemary Syngonium podophyllum Nephthytis Rotala indica Syngonium ‘Red Knight’ Rotala macrandra Thalia dealbata Powdery alligator-flag Rotala rotundifolia Thalia geniculata Swamp lily Rotala wallichii Thuja plicata Western red-cedar Rubus cockburnianus White-stemmed bramble Tonina fluviatilis Rubus tricolor Chinese bramble Trapa natans Water chestnut Rumex cristatus Greek dock Trichocoronis rivularis Sagittaria 'Bloomin Babe' Trichomanes javanicum Sagittaria filiformis Threadleaf arrowhead Tristagma uniflorum Spring starflower Sagittaria graminea Grassy arrowhead Tulipa gesneriana Garden tulip Sagittaria latifolia Duck-potato Typha gracilis Slender cattail Sagittaria lileopterus Typha laxmannii Sagittaria platyphylla Typha minima Sagittaria sagittifolia Typha shuttleworthii subsp. leucopetala Typhonodorum lindleyanum Sagittaria subulata Narrow-leaved arrowhead Utricularia gibba Humped bladderwort Sagittaria teres Slender arrowhead Utricularia sandersonii Salix x calodendron Holme willow Vallisneria americana Salvinia auriculata Vallisneria asiatica Salvinia cucullata Vallisneria natans var. natans Salvinia molesta Giant salvinia Vallisneria rubra Salvinia natans Vallisneria spiralis Tape grass Salvinia oblongifolia Vallisneria tortifolia Samolus valerandi subsp. Water pimpernel parviflorus Verbascum densiflorum Dense-flowered mullein Sasa palmata Broad-leaved bamboo Vesicularia dubyana Sasaella ramosa Hairy bamboo Vesicularia ferriei Weeping moss Saururus cernuus Lizards tail Vesicularia montagnei Christmas moss Saururus chinensis Lizards tail Viburnum rhytidophyllum Wrinkled viburnum Schoenus pauciflorus Viola x wittrockiana Garden pansy Scilla bifolia Alpine squill Yucca recurvifolia Curved-leaved Spanish-dagger Scilla siberica Siberian squill Yushania anceps Indian fountain-bamboo Sedum kamtschaticum Kamchatka stonecrop Zantedeschia aethiopica Altar-lily Sedum spectabile Butterfly stonecrop Selaginella wildenowii Senecio inaequidens Narrow-leaved ragwort Senecio squalidus x viscosus Oxford ragwort Sequoiadendron giganteum Wellingtonia Sisyrinchium striatum Pale yellow-eyed-grass Solanum physalifolium Green nightshade Sorbaria sorbifolia Sorbaria Sorbaria tomentosa Himalayan sorbaria Sorbus hybrida Swedish service-tree Sorghum halepense Johnson-grass Spiraea alba x douglasii Pale bridewort (S. x billardii) Spiraea alba x salicifolia Billard's bridewort
18 HERE TODAY, HERE TOMORROW? Invasive plants and the law Some invasive plants are listed on Schedule 9 of the Wildlife and Countryside Act - which makes it an offence to plant them, or otherwise cause them to grow, in the wild. The plants listed differ in England/Wales and Scotland. The plants currently on the Schedule are:
England and Wales Small-leaved cotoneaster Cotoneaster microphyllus All species of the genus Elodea (waterweeds) Three-cornered garlic Allium triquetrum (including Canadian waterweed Elodea canadensis Variegated yellow archangel Lamiastrum galeobdolon & Nuttall’s waterweed Elodea nuttallii) subsp. argentatum Californian red seaweed Pikea californica Virginia creeper Parthenocissus quinquefolia Curly waterweed Lagarosiphon major Wall cotoneaster Cotoneaster horizontalis Duck potato Sagittaria latifolia Water fern Azolla filiculoides Entire-leaved cotoneaster Cotoneaster integrifolius Water hyacinth Eichhornia crassipes Fallopia japonica x Fallopia sachalinensis (a hybrid knotweed) Water lettuce Pistia stratiotes False Virginia creeper Parthenocissus inserta Water primrose Ludwigia grandiflora / Ludwigia uruguayensis Fanwort (Carolina water-shield) Cabomba caroliniana Yellow azalea Rhododendron luteum Few-flowered leek Allium paradoxum Wakame Undaria pinnatifida Floating pennywort Hydrocotyle ranunculoides Scotland Floating water primrose Ludwigia peploides Californian red seaweed Pikea californica Giant hogweed Heracleum mantegazzianum Curly waterweed Lagarosiphon major Giant kelp Macrocyctis pyrifera, M. angustifolia, M. integrifolia, M. laevis False-acacia Robinia pseudoacacia Giant knotweed Fallopia sachalinensis Fanwort Cabomba caroliniana Giant rhubarb Gunnera tinctoria Few-flowered leek Allium paradoxum Giant salvinia Salvinia molesta Floating pennywort Hydrocotyle ranunculoides Green seafingers Codium fragile Giant hogweed Heracleum mantegazzianum Himalayan cotoneaster Cotoneaster simonsii Giant kelp Macrocyctis pyrifera, M. angustifolia, M. integrifolia, M. laevis Hollyberry cotoneaster Cotoneaster bullatus Giant salvinia Salvinia molesta Hooked asparagus seaweed Asparagopsis armata Green seafingers Codium fragile tomentosoides Hottentot-fig Carpobrotus edulis Hooked asparagus seaweed Asparagopsis armata Indian balsam Impatiens glandulifera Hottentot-fig Carpobrotus edulis Japanese kelp Laminaria japonica Japanese kelp Laminaria japonica Japanese knotweed Fallopia japonica Japanese knotweed Fallopia japonica (Polygonum cuspidatum) Japanese rose Rosa rugosa Japanese seaweed Sargassum muticum Japanese seaweed Sargassum muticum Laver seaweeds (except native species) Porphyra species Laver seaweeds (except native species) Porphyra species New Zealand pigmyweed Crassula helmsii Montbretia Crocosmia x crocosmiiflora Parrot’s-feather Myriophyllum aquaticum New Zealand pigmyweed Crassula helmsii Shallon Gaultheria shallon Parrot’s-feather Myriophyllum aquaticum Water fern Azolla filliculoides Perfoliate Alexanders Smyrnium perfoliatum Water hyacinth Eichhornia crassipes Purple dewplant Disphyma crassifolium Water lettuce Pistia stratiotes Red algae Grateloupia luxurians Wakame Undaria pinnatifida Rhododendron Rhododendron ponticum Rhododendron Rhododendron ponticum x Rhododendron maximum
Credits Report written and compiled by Sophie Thomas (Plantlife). Rapid Risk Assessments undertaken by Trevor Dines (Plantlife), Andy Byfield (Plantlife) and The Freshwater Biological Association (under a contract from Plantlife). Photograph credit (page10) = Image used under a Creative Commons licence: Attribution-Noncommercial-Share Alike 2.0 Generic Design layout by Andrew Evans
HORIZON SCANNING FOR INVASIVE NON-NATIVE PLANTS 19 Registered Office 14 Rollestone Street, Salisbury, Wiltshire, SP1 1DX. UK Tel: +44 (0) 1722 342730 Fax: +44 (0) 1722 329035 [email protected] www.plantlife.org.uk Speaking up for the nation’s wild plants
Plantlife International - The Wild Plant Conservation Charity is a charitable company limited by guarantee. Registered in England and Wales, Charity Number: 1059559 Registered in Scotland, Charity Number: SC038951 Registered Company Number: 3166339. Registered in England and Wales. ISBN: 978-1-907141-39-3 © 2010
With grateful thanks to The John Ellerman Foundation, the Esmée Fairbairn Foundation and Natural England. The scoring of aquatic plants against agreed criteria was undertaken by the Freshwater Biological Association on a contract from Plantlife. Printed on 100% recycled paper