There’s been a great deal of controversy about whether native plants are best for pollinating insects or whether non-native garden plants are just as valuable. On the whole, the debate has been informed by more opinion than science but, after a four year research project at their Wisley garden near London, the Royal Horticultural Society has the answer. This 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.
“Until now the role native and non-native plants play in sustaining wildlife in gardens has been unclear and confusing,” say the lead researchers on the project Dr Andrew Salisbury and Helen Bostock. “Now, for the first time, gardeners can access robust, evidence-based information on the most effective planting strategy they can adopt if they wish to attract and support pollinators.”
Over on her Plants For Bugs blog, Helen Bostock summarizes the three main conclusions of the research (her emphasis in bold).
“1. The best strategy for gardeners wanting to support pollinating insects in gardens is to plant a mix of flowering plants from different countries and regions.
“2. Emphasis should be given to plants native to the UK and the northern hemisphere, though exotic plants from the southern hemisphere can be used to extend the season (there are a greater proportion of exotic plants flowering later in the season compared to UK native and northern hemisphere plants) and provide nectar and pollen for some specific pollinators.
(Left, Verbena bonariensis from South America)
“3. Regardless of plant origin (native or non-native), the more flowers a garden can offer throughout the year, the greater the number of bees, hoverflies and other pollinating insects it will attract and support.”
So there you have it, research at the RHS (part of the research area above, click to enlarge) the best way to encourage pollinating insects is to “plant a mix of flowering plants from different countries and regions” – and not to rely only on native species.
Supported by the Wildlife Gardening Forum, this is exactly the sort of research we need to demonstrate the proven realities of an issue which has been dominated by the trading of opinions such as “Native plants will attract more native pollinators” masquerading as facts.
Let’s hope the RHS team will soon be looking at the relative importance of native and non-native plants in providing food for those larvae of native insects which do not require specific native plant species on which to feed – for although the point is pretty much proved in Jennifer Owen’s Wildlife of a Garden, it would be good to have research on the same scale this newly published RHS research to make the point.
* You can read the full details of the RHS research online in the Journal of Applied Ecology.
* Take a look at the latest addition to the RHS guidance on Plants For Pollinators based on this research.
* Read the background to the research and how it was done.