Plants banned by the European Union in 2016

A new regulation from the EU placed stringent controls on 14 non-native invasive plants from 1 January 2016

These are species that have been assessed as posing such a high risk of invasion within one or more EU member states that a co-ordinated, Europe-wide response is needed to limit their spread. Therefore, it will become an offence to keep, cultivate, breed, transport, sell or exchange these species, or release them, intentionally or unintentionally, into the environment anywhere within the EU. However, there will be no attempt to remove species from peoples’ gardens where they already exist, as long as they are acting responsibly and not encouraging them to spread, (for example, by following appropriate codes of conduct). However, sites in the wild where these invasive species are causing problems should be restored and costs may be recovered in accordance with the ‘polluter pays’ principle, meaning that whoever caused them to spread or be released into the wild may have to foot the bill for subsequent control.

Eight popular plants Of the 14 plant species, eight are plants that have proved popular with gardeners in the past. The following pages give some background information about each one, assess the invasive situation in the UK and gives recommendations on how they should be dealt with. Two are varieties of water primrose so for simplicity’s sake, these are both covered together.

Six lesser-known species The remaining six are plants that are rarely found growing in British gardens (if at all). However, a brief summary of each is included at the end for completion.

Photographs l American skunk-cabbage, water primrose, floating pennywort and parrot’s feather © GB NNSS l Curly waterweed, Carolina watershield © RPS Group l Water hyacinth: © Gabriela Ruellan under Creative Commons by 2.0 licence American skunk-cabbage (Lysichiton americanus) Under European Union regulations, it is an offence in the UK to keep, cultivate, breed, transport, sell or exchange this species, or release it, intentionally or unintentionally, into the environment

What is it? A huge, imposing perennial producing paddle-shaped leaves up to 1.5 metres tall and yellow arum-like flowers in spring that are spectacular but foul-smelling (hence the name). Originally from western North America, it was widely available from garden centres and nurseries for planting besides ponds and in bog gardens.

Why has it been banned? It spreads vigorously in wet woodland, wetlands and ditches, forming dense stands that out-compete native vegetation by shading and smothering. Reproduction by seed in the wild is frequent. It has been reported in at least 10 EU countries.

What’s the situation in the UK? A popular plant, grown in British gardens since at least 1901. Although known in the wild since 1905, it’s being reported with increasing frequency: up by 84% in 15 years. In the New Forest , for example, it has become dominant in some wet alder woodlands and on the River Lymington, eradicating almost all the native ground flora (such as bluebell, wood anemone and sanicle) in some sites.

How does it spread? By underground rhizomes and by seed, which can be carried hundreds of metres away in water to establish new colonies. As such, sites are appearing at all altitudes, from near sea level to over 250 metres in the Snowdonia and Cairngorms mountains.

What is the cost? Total cost of control at seven New Forest sites has been £9,157 since 2010 and eradication work is expected to last until at least 2020.

Advice? It can be controlled by the targeted use of systemic herbicides, which are easy to apply to the large leaves, or dig plants out and dry thoroughly before composing.

What safe alternatives does Plantlife recommend? l Asian skunk-cabbage (Lysichiton camtschatcensis) is a slightly smaller, less invasive species with beautiful white flowers l Lysichiton × hortensis a cream-flowered hybrid between the American and Asian species, reported to be sterile and therefore cannot spread to new sites Carolina watershield (Cabomba caroliniana) Under European Union regulations, it is an offence in the UK to keep, cultivate, breed, transport, sell or exchange this species, or release it, intentionally or unintentionally, into the environment

What is it? An aquatic plant from subtropical temperate areas of eastern North America and southern South America. Its long stems are clothed in attractive feathery leaves and it occasionally produces white flowers above the water. It can be found in the still or slow-flowing waters of lakes, ponds, ditches and canals, and growth rates of up to 5cm a day have been reported.

Why has it been banned? It grows very densely, impacting native vegetation, water quality and fishing. It has been reported widely as an invasive species (including Asia, Australasia and North and South America) and is naturalised in six EU countries.

What’s the situation in the UK? One of the most popular aquatic plants for tropical fish tanks, it grows easily and quickly and is highly decorative. Coming from subtropical-temperate areas, it grows best between 13—27°C and in 1969 was discovered growing happily in a section of the Forth & Clyde Canal that received heated water from a nearby factory. Normally, British winters should kill it off, but the discovery of a colony in an unheated section of the Basingstoke Canal in 1990 (it is still there and spreading) indicates this species could become established more frequently, especially in a warming climate.

How does it spread? It produces seed but spreads mainly through its brittle stems breaking into fragments and growing into new plants.

What is the cost? At present, minimal, but control of this species in the Basingstoke Canal should be a priority before it spreads too far, and adequate monitoring should be in place to detect new sites.

Advice? Do not allow it to get out into any ponds or waterways, especially in warm urban areas. In tropical fish tanks, it grows rapidly and needs cutting back frequently, so make sure you dry out cut material thoroughly before composting.

What safe alternatives does Plantlife recommend? l Rigid hornwort (Ceratophyllum demersum), a native oxegenating plant l Red cabomba (Cabomba furcata), but it cannot survive in the wild in the UK Curly waterweed (Lagarosiphon major) Under European Union regulations, it is an offence in the UK to keep, cultivate, breed, transport, sell or exchange this species, or release it, intentionally or unintentionally, into the environment

What is it? An aquatic plant from South Africa commonly sold as an oxygenator for ponds and aquaria. It produces long, branching, submerged stems that are densely clothed with dark green pointed leaves that curl sharply back towards the main stem. Produces dense mats up to three metres thick.

Why has it been banned? It can grow to dominate entire ponds and it also occurs in lakes, canals and flooded mine workings and gravel pits. Its mats shade everything below them, blocking light to native aquatic plants such as pondweeds and water-milfoil, as well as invertebrates. It alters the water, making it more acidic, therefore reducing the photosynthetic ability of other species. It is widely naturalised in western Europe (11 countries) and is a serious invasive problem in New Zealand.

What’s the situation in the UK? Sold at many garden centres, it was first recorded naturalised in the wild in 1944 and has now been recorded from 645 10km squares, mainly in southern and north-west England and South Wales. Many introductions appear to arise from intentional plantings or throw-outs from ponds and aquariums. It does considerable damage, both ecologically and economically.

How does it spread? Even tiny stem fragments can grow into new colonies, assisting its spread to new sites via accidental contamination by boats, machines, clothing or animals.

What is the cost? Considerable. For example, reducing an infestation in Lough Corrib, the second largest lake in Ireland important for its salmon and trout fishing, from 100ha to 10ha cost over €1.5 million (£1.06 million).

Advice? Carefully hand pull as much material as possible. Small fragments will regrow so control will probably be needed for a few years. Alternatively, remove the plants and livestock you want to keep and cover the pond in very thick black plastic (to exclude light) for six months.

What safe alternatives does Plantlife recommend? Good alternative native oxygenating plants include: l Rigid hornwort (Ceratophyllum demersum) l Curly pondweed (Potamogeton crispus) l Spiked water-milfoil (Myriophyllum spicatum) Floating pennywort (Hydrocotyle ranunculoides) Under European Union regulations, it is an offence in the UK to keep, cultivate, breed, transport, sell or exchange this species, or release it, intentionally or unintentionally, into the environment

What is it? This very popular and widely available aquatic plant forms dense mats of rounded leaves that float across the water surface.

Why has it been banned? It grows rapidly, forming floating blankets that exclude light and clog water channels.

What’s the situation in the UK? First recorded in the wild in Britain in 1990 and widely sold for gardens and aquariums, this species — originally from North America — is now recorded from 163 10km squares in the wild, showing how quickly these invasive species can spread when introduced through horticulture.

How does it spread? It grows very rapidly, forming floating blankets that exclude light and clog water channels.

What is the cost? Control is expensive and time-consuming. It appeared on the River Soar around Leicester in 2004 and spread quickly. Despite years of hand pulling by volunteers and herbicide application, complete eradication appears to be impossible, and £20,000 was spent on control measures in 2014.

Advice? Floating pennywort is difficult to control due to its rapid growth rates (up to 20cm per day) and its ability to regrow from a small fragment. Regular cutting from May to October will prevent complete dominance and so help manage this plant. Cut material needs to be removed from the water immediately. Hand pulling (or spot chemical treatment) should follow cutting to reduce regrowth. Pulling is likely to work best on small infestations rather than larger areas. Chemical treatment should only be used at the end of the growing season when all other plants have died back.

What safe alternatives does Plantlife recommend? l Marsh pennywort (Hydrocotyle vulgaris)

Parrot’s feather (Myriophyllum aquaticum)

Under European Union regulations, it is an offence in the UK to keep, cultivate, breed, transport, sell or exchange this species, or release it, intentionally or unintentionally, into the environment

What is it? This popular pond plant produces long stems and floating mats of attractive feathery leaves. It may be sold as Brazilian water-milfoil (Myriophyllum brasiliense or Myriophyllum proserpinacoides).

Why has it been banned? Vigorous growth allows it to become dominant in ponds, lakes, reservoirs, ditches and canals. It grows to such an extent that it can choke water bodies and out-compete native vegetation, blocking light and altering patterns of flow.

What’s the situation in the UK? More widely established in the wild than water primrose and floating pennywort (it’s been recorded in over 480 10km squares, mostly in southern England) and, therefore, much more of a challenge to control, this rampant aquatic rapidly over-runs ponds, ditches, canals and reservoirs. At Shortwood Common Pond, one of the richest ponds in England for plant and insect life, the spread of parrot’s heather has led to the loss of brown galingale (Cyperus fuscus), a rare pond-side sedge.

How does it spread? It can root from small stem fragments and readily escapes into the wild.

Advice? Regular cutting (at least every 6-9 weeks during the growing season - cut more frequently if necessary) will help to weaken the plant. In your garden pond you can thin using a rake. Cut material must be removed from the water as soon as possible and all fragments need to be removed to prevent regrowth (or spread downstream if you are clearing an area of river). Careful pulling out of stems by hand will help eradicate small colonies and after cutting.

What safe alternatives does Plantlife recommend? l Spiked water-milfoil (Myriophyllum spicatum) l Alternate water-milfoil (Myriophyllum alterniflorum) Water hyacinth (Eichhornia crassipes) Under European Union regulations, it is an offence in the UK to keep, cultivate, breed, transport, sell or exchange this species, or release it, intentionally or unintentionally, into the environment

What is it? A remarkable floating aquatic plant from the Amazon basin which produces rosettes of floating leaves, each with a swollen, air-filled stalk and spikes of attractive blue flowers in summer. In tropical and sub-tropical climates, it spreads with remarkable speed on lakes, reservoirs and slow-moving rivers to form vast, dense floating mats.

Why has it been banned? It’s widely regarded as the world’s most troublesome invasive plant in frost-free areas, being reported from 133 countries and causing severe biological, economical and social impacts in many of these. In Europe, it is reported from eight countries, but is not currently regarded as invasive in any of these. It could become a problem in southern Europe if climate warming continues.

What’s the situation in the UK? This species is popular in gardens, but because it’s not hardy here, it’s treated like a summer bedding plant for ponds. In the wild, it’s been recorded from about 36 sites in total, mostly during the period 2000­—2009, but almost all of these are transient and don’t survive the winter. The optimum temperature for growth is 25—30°C, although short periods at freezing can sometimes be tolerated. And there is one case where plants appear to have survived the very mild winter of 1989/1999 in a ditch in north London.

How does it spread? It produces seed but spreads mainly through its brittle stems breaking into fragments and growing into new plants.

What is the cost? Little — our climate is not conducive to its growth.

Advice? Try growing some of our recommended, safe alternatives (see below).

What safe alternatives does Plantlife recommend? Native floating aquatic plants such as: l Frogbit (Hydrocharis morsus-ranae) l Water-soldier (Stratiotes aloides) Water primrose (Ludwigia grandiflora and Ludwigia peploides) Under European Union regulations, it is an offence in the UK to keep, cultivate, breed, transport, sell or exchange this species, or release it, intentionally or unintentionally, into the environment

What is it? Originally introduced as an ornamental and water garden plant, the water primrose bears bright yellow flowers but can cause havoc if released in the wild. It is difficult to distinguish between the species of Ludwigia and they are often incorrectly labelled, so it may be necessary to seek expert advice.

Why has it been banned? Water primrose can have a devastating effect on native habitats. Its rampant growth out-competes native species and can clog waterways, with its dense vegetation contributing to flooding. It has been particularly problematic in parts of Europe; in the UK it is on a Rapid Response list, meaning that any known sites, of which there have been a handful, are targeted for immediate eradication.

What’s the situation in the UK? First recorded in the wild in Britain as recently as 1999, it has now been found growing at about 19 sites and is proving to be stubborn and almost impossible to eradicate at some. Repeated herbicide control from 2009—2012 at Breamore Marsh SSSI (Hampshire), a site for great crested newt and brown galingale, had no effect, so the entire pond was excavated in 2013 and the infected material buried in a nearby site and capped to prevent further spread.

How does it spread? Primarily by stem fragments, but also by seeds which means it can spread quickly and it can make eradication difficult.

Advice? Regular cutting (at least every six to nine weeks during the growing season — cut more frequently if necessary) will help to weaken the plant. In your garden pond you can thin using a rake. Cut material must be removed from the water as soon as possible and all fragments need to be removed to prevent regrowth (or spread downstream if you are clearing an area of river). Careful pulling out of stems by hand will help eradicate small colonies and after cutting.

What safe alternatives does Plantlife recommend? l Lesser spear-wort (Ranunculus flammula) Cooler climate plants rarely grown in the UK

Tree groundsel (Baccharis halimifolia) What is it? A large shrub from eastern North America grown for its dense heads of small, daisy-like flowers. It grows in coastal situations from Connecticut south to Florida and the Bahamas, and is highly invasive in parts of Australia (especially sub-tropical areas), New Zealand and Europe (France, Spain and Italy), where it invades saltmarsh habitats. In the UK? This species was very rarely grown in gardens. In the wild, it has been recorded from just three sites — at the most famous of these, at Mudeford in Dorset, it was planted beside a car park and has shown no sign of spreading since being found in 1924.

What should we do about it? Given its invasive character abroad, any UK populations should be monitored periodically. Control should be undertaken if there is evidence of spread.

Persian hogweed (Heracleum persicum) What is it? One of several large hogweeds, the ground seeds of this species are a popular flavouring (known as Golpar) in Persian cooking. The plant comes from cool, mountainous parts of Iran and, following its introduction in the 1830s, has become invasive in parts of Norway. In the UK? This species has been found in the wild a few times, but only three sites have been reported in the last 15 years. It does not appear to be behaving invasively and it’s rarely grown in Britain (it’s not listed in the RHS Plant Finder). What should we do about it? Some species of hogweed are highly invasive, so it’s important that we monitor the escape and spread of all non-native Heracleum in the wild. Since this species is invasive in Norway, we should be alert for populations becoming established in areas with a similar climate here and control should be undertaken if there is evidence of spread.

Sosnowskyi’s hogweed (Heracleum sosnowskyi) What is it? One of several species of giant hogweed, this species can reach a height of five metres. Originally native to the Caucasus, it is now an invasive weed in eastern Europe, Poland and Russia. In the UK? This species has never been found in the wild in the UK. It’s rarely grown in Britain (it was last listed in the RHS Plant Finder in 2010). What should we do about it? Although not currently a problem in the UK, some species of hogweed are highly invasive so it’s important that we monitor the escape and spread of all non-native Heracleum in the wild. Warmer climate plants not grown in the UK

Parthenium weed (Parthenium hysterophorus) What is it? A highly invasive annual weed that rapidly colonises bare, disturbed soil. It’s a tropical species native to southern United States, Mexico and Central and South America, and has become a serious agricultural weed in many parts of the southern hemisphere. It can persist in areas where the average temperature is above 10°C, and has been reported from Poland and Belgium but only as transient occurrences that didn’t persist. In the UK? This species is not grown in the UK and has never been recorded in the wild.

What should we do about it? Monitor any occurrences and spread in southern Europe.

Mile-a-minute weed (Persicaria perfoliata/Polygonum perfoliatum) What is it? A fast-growing, herbaceous vine from Asia, rather like a bindweed, that scrambles up to a height of six metres and clothes other plants, shrubs and trees. Although native to tropical and sub-tropical areas, it has become established and invasive in parts of North America, from Virginia northwards to New York. It also appears to be capable of surviving in areas where the average minimum temperature is above 0°C and is known to be invasive in the warmer temperate parts of west Turkey. In the UK? Mile-a-minute weed (not to be confused with mile-a-minute vine (Fallopia baldschuanica) is not grown in the UK and has never been recorded in the wild, but it’s tolerance of colder climates in North America means it could become established here. What should we do about it? The ban on trade is helpful, as it was first established in the USA following its introduction to a nursery site. It could potentially flourish in the warmer and wetter parts of the UK, so it’s one to keep out.

Kudzu vine (Pueraria montana var. lobata) What is it? A tropical vine native to East Asia. This climbing bean was widely introduced to India, North and South America and Australasia, but has only become highly invasive in the warmer parts of North America where it was originally planted to prevent soil erosion. It’s been recorded growing 25cm a day and can smother building and telegraph poles, as well as severely impacting native habitats. It has been recorded in the wild in Italy and Switzerland, but is not regarded as invasive. In the UK? This species was not normally grown in the UK and hasn’t been recorded in the wild. What should we do about it? Since Kuzdu vine needs average minimum temperatures above 0°C, it could grow in warmer and wetter parts of the UK, but is unlikely to become invasive. Any new occurrences should be closely monitored.