Your Wildlife Gardening Gateway

Plants for Bugs Project

...bringing nature closer to home

By Helen Bostock and Andrew Salisbury  Reviewed by Steve Head

 

Studies into biodiversity in urban gardens at the University of Sheffield ending in 2007  demonstrated that garden habitats were able to support a rich diversity of plant and animal species. However, despite 70% of plants in the average UK garden being non-native (i.e. of origin outside Britain), the dominant advice to gardeners wishing to garden with wildlife in mind has been to use British native plants. This suggested that the role of native and non-native plants was unclear and would benefit from further research.

 

Consequently, in April 2007 the Research Working Group of the Wildlife Gardening Forum approached the Royal Horticultural Society  with a research proposal. This developed into the study known as the ‘Plants for Bugs’ project, the purpose of which was to compare British native and non-native garden plantings for invertebrates. It was considered that “bugs” (aka invertebrates) – of which gardens contain thousands of species of many different functional groups (e.g. predators, herbivores, detritivores, pollinators, etc) – would provide a good reflection of the ecological health of a plot planted with a selection of garden plants. The essential question posed by the project was “Do bugs care about the geographical origin of plants in gardens”?

 

The aim of the Plants for Bugs project therefore is to provide evidence-based advice for the wildlife gardener on the use of native and non-native plants.

 

Project set-up

 

The Project Manager is Forum Trustee Helen Bostock, and the Assistant Project Manager is Dr Andrew Salisbury, Forum Chair and convener of the Research Working Group. The project is run at RHS Gardens Wisley, Surrey and was started in 2009, with data collection in 2010 through to 2013.

 

In 2009 thirty-six timber-edged 3×3m plots were planted, equally divided over two sites at RHS Garden Wisley, one at Howard’s Field (open to Garden visitors) and the other at Deer’s Farm (closed to the public). Each plot was separated by a 1m-wide woodchip guard-row.

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A third of the plots were planted with British native plants (referred to as the ‘native’ treatment), a third with closely related species from the Northern Hemisphere (referred to as the ‘near-native’ treatment) and the remaining third with species from the Southern Hemisphere (referred to as the ‘exotic’ treatment). The layout follows a randomised split-plot design with a total of nine planting variations (native A, B and C; near-native A, B and C; and exotic A, B and C). A minimum of 14 (from a total of 24) plant species was selected for each plot to minimize any effect(s) of species choice on the results.

 

The plots are kept as garden-like as possible; hand weed control is carried out to prevent flowering and competition with the plant assemblages, and plants are watered, cut back or staked where required. No pesticides are used on the plots.

Native plant  Eupatorium cannabinum hemp agrimony

Near-native plant  Eupatorium maculatum 'Orchard Dene' Joe Pye weed

Exotic plant Verbena bonariensis   purple top

A fuller account of the project set up is available here and the project leaflet is available here.  To download the list of plants click here

 

Project sampling

 

Invertebrates from native and non-native plots are recorded from the ground (using pitfall and gastropod traps), the foliage (using a Vortis suction sampler) and the air (by visual observations). Soil fauna is also being investigated in a PhD project in association with the University of Roehampton.

 

Other data recorded include plant density and canopy cover (vegetation volume), soil moisture, numbers of flowers, and nectar volume and composition. Specimens are identified to species where possible, or at least guild (a group of species that utilizes resources in a similar way, e.g. predator, generalist herbivore etc.).

 

Collecting invertebrates with a Vortis sampler and measuring the 3D density of the foliage on the plots

 

By the end of December 2013 approximately 80,000 invertebrates had been counted and more than 300 species identified.  This includes more than 8,000 flying insects visitors (pollinators),  47 species and nearly 2,000 specimens of ground beetle (Carabidae) and more than 30 species of spider. 

Project results and interpretation

 

During 2014 the data from the four years of project is being analysed and the results prepared for publication, the first paper is expected to be published in early 2015.  Early indications from provisional analysis indicate that the data will provide useful insights into the ecological role of native and non-native plants in gardens.  In addition to scientific publications the results will be interpreted to provide advice for gardeners who wish to increase biodiversity in their own gardens.

Project team: Helen Bostock (Project manager, RHS), Andrew Salisbury (RHS) Andrew Halstead, James Armitage (RHS botanist), Joe Perry (consultant statistics/ design), Suzanne Clark (Statistics, Rothamsted Research), Mark Tatchell (consultant), Sarah Al-Beidh (KTP), Stephanie Bird (University of Roehampton, PhD Student)

 

External taxonomic expertise: Jonty Denton (Spiders & Leafhoppers), Scott Lawton (Kingston Uni. gastropods), David Notton (NHM, Hymenoptera: Parasitica), Peter Shaw (University of Roehampton, Collembola)

 

Methodology/statistical advice: David Brookes, Suzanne Clark, Alison Haughton & Juliet Osborne

 

Volunteers: Carolyn Hewitt, Judi O’Prey, Linda Moyes

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