What are native and non-native plants?

Gardeners in the UK often use a combination of plants from around the world. Some plants grown by gardeners are classed as native, meaning they occur naturally in Britain (i.e. have not been introduced by humans). Other garden plants originate from regions outside Britain, perhaps only from elsewhere in Europe or similar temperate regions of Asia or North America. Or they may originate from southerly regions such as South Africa or Australia where the climate and habitat may be very different from that in Britain. We have such a rich choice of plants in UK horticulture, thanks in no small part to the legacy of plant hunters who brought back many new and interesting plants from their travels.

When talking about plant origins we have divided them into three categories - one native and two non-native;

• British (native)
• Northern hemisphere excluding Britain (non-native – Northern, also here termed 'near-native')
• Southern hemisphere (non-native – Southern, also here termed ‘exotics’)

Poke about among the leaves and stems of your plants and you will discover an exciting world home to hundreds of species. These invertebrates are incredibly varied but can be divided into one of four primary functional groups based on what they eat;

Herbivores

Examples: caterpillars and beetles (chewing mouthparts), thrips, aphids and other true bugs (sucking mouthparts)
Food chain function: eat living plants. The group contains generalists which are able to feed on a wide range of plants and some very specialist feeders which only feed on a few plant species. They sometimes damage garden plants

Predators

Examples: predatory beetles (e.g. ladybirds), true bugs, spiders and parasitoid wasps
Food chain function: eat other animals. They are vital in any healthy ecosystem and help keep some problematic invertebrates in check, including many herbivores

Omnivores

Examples: the harvestman (relative of the spider) and common earwig (feeds on other insects, such as aphids, as well as the leaves of some plants)
Food chain function: eat both plants and animals. This broad feeding strategy makes them very adaptable if one food source becomes scarce

Detritivores

Examples: springtails, woodlice and some beetles that feed exclusively on dead material
Food chain function: eat decomposing organic matter, of animal or plant origin. They are vital in recycling dead material in the garden. Many also feed on fungal and algal growths

Why are these invertebrates important?

While some of these animals are traditionally regarded as pests by gardeners, they support populations of natural predators, which in turn help maintain a balance of invertebrates in general. They break down dead plant material and recycle nutrients. They also provide food for garden birds and mammals such as hedgehogs. In short, an abundance of bugs of all types equates to a healthy garden ecology.

Does a plant's origin affect how well it supports these invertebrates?

In the context of garden plants, it would appear plant origin does have a bearing. However, other factors such as vegetation density also play an important role. Below are the findings and recommendations to gardeners from recent research.

1. The best strategy to support invertebrates living in the greenery in your garden is to use predominantly British native plants.
2. Even if you don’t have a lot of British native plants in your garden, planting schemes based on near-native plants may support only marginally fewer invertebrates. This applies both overall (less than 10% fewer) and in three of the four primary invertebrate functional groups investigated (herbivores, predators and detritivores).
3. Planting schemes based on exotic plants will still support a good number of invertebrates, albeit around 20% fewer than British natives.
4. Regardless of plant origin, the more densely you plant your garden or allow it to grow, the more invertebrates of all kinds (herbivores, predators, detritivores and omnivores) it will support.

How to apply this in the garden

Enhance your garden for invertebrates living in the greenery through plant choice:

• Think closer to home – plant plenty of British native plants to support maximum herbivores, predators, detritivores and omnivores
• Decide priorities – planting a greater proportion of exotic (Southern hemisphere) plants may support marginally fewer herbivores but will help extend the season for certain pollinators
• Let it fill out – whatever you decide to plant, allow plants to fill the space to maximise foliage cover
• Plant generously – to obtain the same number of invertebrates as from a plot of British native plants, you would need about a fifth more near-native (Northern hemisphere) vegetation, and about a quarter more exotic (Southern hemisphere) vegetation
• Be relaxed – tolerate some nibbled leaves, don’t spray at the first sign of damage and allow some plant debris to accumulate if you want to support your garden’s food chain

What should I plant?

Our research is not prescriptive on exactly which plants you should plant in your garden but here are a few pointers to help you put into practise the principles described above.

So, if your garden lacks British native plants or you’re not sure what these are, these pages will help;

• RHS Find a Plant list of British natives
• Trees and shrubs native to Britain
• RHS Plants for Pollinators wildflower list

British wildflowers such as primroses, foxgloves and hemp agrimony can simply be slotted into conventional beds and borders. Alternatively, you can dedicate an area to a wildflower meadow. Be inspired;

• How to establish a wildflower meadow
• How to maintain a wildflower meadow
• Plantlife (wildflower plant charity) guide on gardening with wildflowers

Or maybe you’d particularly like to focus your planting on encouraging one group of invertebrates – the pollinating insects (e.g. bees and hoverflies) – in which case our research suggests exotic plants such as fuchsia, hebe and single-flowered dahlias will help to extend the season with pollen and nectar-rich flowers. Here’s more on planting for pollinators;

• RHS Plants for Pollinators plants of the world list

And remember, the good news is that any planting is better than none, and garden plants originating from all regions in our experiment supported a good number of invertebrates.

RHS Plants for Bugs research

Plants for Bugs was a four-year study into wildlife gardening, which was undertaken at RHS Garden Wisley in Surrey, and supported by the Wildlife Gardening Forum. Read here for more about the design of the experiment and plants used in the study. The first scientific paper reported on pollinating insects visiting the flowers and the third paper reported on invertebrates living at ground level.

Recording invertebrates living in the greenery

Results from the second scientific paper focused on invertebrates living on the leaves and stems (termed 'plant-associated invertebrates'). In total nearly 23,000 individual invertebrate specimens were collected directly from the plants using a Vortis suction sampler (an insect vacuum). Each plot was swept with the suction sampler on five or six occasions each year, with every plant species on a plot being sampled. Samples were sorted and identified in the laboratory.

Further reading

• Read the academic paper abstract
• Read the interpretation bulletin 2
• Read the results from paper 1 – Native and non-native plants for pollinators
• Read the results from paper 3 – Native and non-native plants for ground-active invertebrates