Over several centuries gardens in the UK have been enriched by the introduction of plants from outside the UK referred to as non-native plant species. Such plantings, when controlled, have added colour, aesthetically pleasing form and texture, and in some cases have provided other environmental benefits. In many cases these plant species have become naturalised and continue to be planted extensively.
However, some non-native plant species have escaped control and have become highly invasive, threatening natural habitats and native plant species, and causing detrimental ecological impacts. Often such species outcompete native plants either by habitat change or by spreading so rapidly as to crowd out slower growing native species, threatening their long-term survival. Invasive non-native plants can often take over an area quickly, choking off native plants and removing food sources and breeding habitats for other wildlife species.
Some of the invasive non-native plant species have taken a long time to become invasive, with several of these growing in the UK for over 100 years during which time they showed no sign of becoming a problem.
New Zealand Pygmyweed
The most common invasive non-native plants in the UK include:
Such invasive non-native plants can change ecosystems and habitats and, in some cases, have non-biotic effects, such as reducing or impeding water flow leading to flooding, or changing the chemical composition of the soil, locking up nutrients, or changing the pH of the soil.
There are of course other species that are considered invasive non-native species, and these are identified in various laws applicable in the UK. In England it is an offence to plant or cause to grow in the wild plants listed on Schedule 9 of the Wildlife and Countryside Act (1981). In April 2014 a ban came into force on sale of five of the worst invasive water plants in the UK.
By not allowing non-native plants to escape from gardens and disposing of unwanted plants carefully, gardeners can help reduce the spread of invasive non-native species. The Royal Horticultural Society has some very useful and practical information on what to do if you already have invasive non-native species on your land – and what you should do – read more here. Also the UK Government has some good information on the legalities and most importantly the laws governing the disposal of invasive non-native species once you have dug them up – more details here. The Woodland Trust is particularly concerned about the long-term damage to our woodlands when invasive species take over. You can read more information here
We hope this blog helps you to recognise and manage non evasive species in your garden to prevent them spreading into our countryside.