Working on Plants for Bugs plotsPlants for Bugs is a four-year study into wildlife gardening, which was undertaken at RHS Garden Wisley in Surrey, and supported by the Wildlife Gardening Forum.

It is a unique study as it is the first ever designed field experiment to test whether the geographical origin (‘nativeness’) of garden plants affects the abundance and diversity of invertebrates (wildlife) they support.

Views differ on whether only native plants should be planted in a wildlife-friendly garden or whether non-native species also have a place.

Why do we need the research?

Biodiversity is being reduced on a global scale – but the good news is that gardens provide a haven for some species. Wildlife gardening is not just about putting up bird boxes or ladybird houses – growing plants is just as important. These create a habitat for all sorts of insects and can be an important food source for one or more stages in their life cycles.

It’s confusing to know what is best to plant. Some advice suggests only British native plants are good for wildlife. Other advice lists specific plants, but these might include a mixture of natives such as foxglove and non-natives such as buddleja.

We realised new research was needed to look into the question of whether the geographical origin of a garden plant is a significant factor in biodiversity richness. An average garden contains around 70% non-native plants to just 30% British native plants. Data from the Plants for Bugs study is beginning to reveal if there are any recordable differences in invertebrate numbers and species between these plant groups. This will allow us to help gardeners make informed plant choices when gardening for wildlife.

How was the research undertaken?

The project consisted of 36 plots (each 3x3m [10x10ft]; the size of a typical garden border) on two sites, one within RHS Garden Wisley and the other on the adjacent Deers Farm research field. To make a comparison between garden plants, beds were prepared in summer 2009, each bed containing plants from one of three geographical zones.

• UK (Native)
• The northern hemisphere excluding the UK (non-native – Northern)
• The southern hemisphere (non-native – Southern)

Each bed was planted with a mix of 14 species of plants, including bulbs, perennials, shrubs, grasses, ferns and a climber, and designed to be typical of a small garden border.

Monitoring invertebrates

Four methods were used to monitor the invertebrates on the beds, largely at six-week intervals between March and October.

  • Slug and snail traps – these are upturned plant saucers over a chicken-feed bait set in the middle of each bed.
  • Pitfall traps – these are a plastic beaker sunk into the middle of each bed and part-filled with preserving fluid to capture ground fauna such as ground beetles and woodlice.
  • Suction sampling – this method uses a ‘Vortis suction sampler’ (pictured right) that we sweep slowly over the plant foliage to suck up insects such as flies, aphids, caterpillars, plant bugs, leafhoppers, beetles and their larvae.
  • Observation of flower-visiting insects – this method depends on the weather conditions being favourable for flying insects such as bees, wasps, butterflies, flies (including hoverflies) and adult beetles. An observer notes on a record sheet those seen landing on the flowers.

Results so far

By the end of December 2013 (four full years of recording) approximately 80, 000 invertebrates had been counted and more than 300 species identified. The first peer-reviewed paper looking at the results from the pollinating insect data has been published in August 2015.

Findings for other invertebrate groups studied (herbivores, predators, decomposers, etc.) will be published in further papers and interpretation for gardeners made available on the RHS website.

Download the full list of plants used in the Plants for Bugs project (12kB pdf)

Download background information on the Plants for Bugs project at RHS Garden Wisley (2MB pdf)

See the full RHS Plants for Bugs press release.

For more about life on the plots read Helen Bostock’s Plants for Bugs blog.

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