Non-native invasive species can:
- Change ecosystems and habitats and have non-biotic effects, such as reducing or impeding water flow leading to flooding, or changing the pH or the chemical composition of the soil, or lock up nutrients
- Outcompete native species either by habitat change or by spreading so rapidly as to crowd out slower growing species, threatening the long-term survival of species
- Take a long time to become invasive. Many of the plants now considered invasive have been growing in the UK for over 100 years and for much of that time showed no sign of becoming a problem
- Be expensive to eradicate. It is also very costly to restore degraded habitat, if it can be done at all
FACT: There are 1,402 non-native plants established in the wild in Great Britain, of which 108 (8%) are stated to have a negative impact.
What UK legislation covers invasive non-native plants?
The Wildlife and Countryside Act (1981) recognised the need to control certain species of invasive plants and animals already causing a problem in the UK, listing them in Schedule 9. Originally only giant hogweed (Heracleum mantegazzianum) and Japanese knotweed (Fallopia japonica) were listed. However, in April 2010 a further 36 plants were added onto Schedule 9 (see below for a download of the list). A recent amendment to the Wildlife and Countryside Act has a new provision to ban specific plants from sale. In April 2014 a ban on sale of five of the worst invasive water plants in the UK came into force. The five species banned from sale are:
†Ludwigia grandiflora and L. peploides
The development of policy and legislation in relation to the environment is one of the areas that falls under the devolved administrations;
- Wales: covered by the Wildlife & Countryside Act but with separate amendments
- Northern Ireland: covered by the Wildlife and Natural Environment Act (Northern Ireland) 2011. This includes a provision for the ban on sale of animal and plant species listed in Schedule 9, as specified in an order issued by Northern Ireland Executive Department of the Environment. At the present time it is not clear whether any such order has been made
- Scotland: a new Wildlife and Natural Environment Act (Scotland) 2011 is now in force making it illegal to plant any non-native plant in the wild in Scotland
FACT: It is a criminal offence to plant or cause to grow a non-native invasive species that is listed on Schedule 9 in the wild which carries penalties of up to £5,000 fine and/or 2 years imprisonment.
Republic of Ireland
The Irish Government adopted in 2011 the European Communities (Birds and Natural Habitats) Regulations in which Schedule 3 provides a list of species which it is an offence to (a) cause to grow, disperse or spread in the wild and (b) possess, propagate, offer, distribute or import with the intention of making available for sale. However the relevant clauses of the legislation have not yet been made effective and will only be so by public announcement by the relevant Minister.
What is in place to help tackle the problem?
The Convention on Biological Diversity (1992) included a requirement for signatories to prevent the introduction of, control or eradicate those alien species which threaten ecosystems, habitats or species. This led to the formation of the Global Invasive Species Programme in 1997 which published the Global Strategy on Invasive Alien Species in 2001.
Within the UK, legislation on non native species was reviewed in 2001 which led to the formation of;
Alongside these developments, working with the horticulture industry, the Department for the Environment, Food and Rural Affairs (Defra), published the revised Horticulture Code of Practice for England and Wales in 2011 which provides non-binding guidance to horticulture professionals and gardeners on dealing with non-native invasive species. There is also a Horticultural Code of Practice for Scotland.
Invasive plants covered by legislation in the UK and Ireland
The EU Regulation on Invasive Alien Species, which became law early in 2015, has a provision for a list of species of EU-wide concern. That list has now been published by the EU Commission and will become effective from March 2016. Species that are included in the list attract the strictest measures of control, including a ban on keeping, growing or cultivating, transporting or trading, use or exchange, as well as release into the wider environment. These controls will apply to individuals as well as organisations and businesses that own or hold any of these species.
There are 14 plants on this list, most of which are of marginal importance to gardeners, or are already banned from sale in the UK (marked with † in the above list), but two widely grown species, Eichhornia crassipes (water hyacinth) and Lysichiton americanus (skunk cabbage) are included. Although there are transitionary measures allowing businesses to sell off their stock of these species within one year, to minimise potential for confusion, we have taken the step of not listing the species in the 2016 RHS Plant Finder. Those species affected are:
Baccharis halimifolia (tree groundsel)
Cabomba caroliniana (Carolina fanwort)
Eichhornia crassipes (water hyacinth)
Ludwigia peploides (water primrose)
Lysichiton americanus (American skunk cabbage)
Parthenium hysterophorus (Parthenium weed)
Pueraria montana var. lobata (Kudzu)
Gardeners who already have these species in their gardens are not at risk of prosecution for possession as the Regulation is not retrospective, but will be required to meet the other requirements of the Regulation to ensure that they control the species effectively on their property and do not allow it to spread.