For a long time, it was accepted 'knowledge' that the best plants for wildlife to grow in gardens were 'native' plants.
It was the Biodiversity in Urban Gardens in Sheffield (BUGS) project, driven by the uncompromising Dr Ken Thompson, that began to challenge that assumption. After all, what plant do we all consider the best for nectaring butterflies? Yes, Buddleia, from Asia (although now there are concerns about its invasiveness).
And what exactly is a 'native' plant, given that many species we think of as native, such as poppies, aren't. I summarised the conundrum in RSPB Gardening for Wildlife (I allow myself the plug. given that it has raised several thousand pounds for nature!).
Now, important new bits of science are underway, setting hypotheses and testing the benefits or otherwise of growing native and non-native plants. So, on Monday, it was with some anticipation that I attended the Wildlife Gardening Forum's major conference at Wisley to hear the preliminary results of the RHS's Plants for Bugs project.
And, blimey, what a project they have undertaken. For four years, the RHS staff and volunteers have tended and studied 36 plots, each of 3m x3m. Twelve are planted with native plants, 12 with 'near natives' and 12 with non-natives. My thanks to my lovely RSPB colleague, Kathy Berkery, for remembering to take some photos of the plots (below). (Kathy is another of those RSPB staff who, like me, has an RSPB day-job but is mad keen passionate about gardening in her spare time).
The RHS has studied the creatures that live in the soil in those plots, which has meant counting thousands of microscopic springtails.
They've captured 35,000 invertebrates in pitfall traps, which are where surface creatures such as spiders and ground beetles drop into buried plastic cups.
They've sucked at the foliage with a giant vacuum cleaner and counted and identified whatever creatures it caught.
And they've stood and counted bees and butterflies visiting the plots.
The results are still wrapped in big caveats, but here are some of the headlines that appear to be emerging:
Plant-choice in those beds will of course have played a huge part - growing a different selection of plants would probably make a huge difference.
But it is great to have some solid science as another piece of the jigsaw in understanding how we can best give nature a home in our gardens.
In my book, I said that "the question of native plants versus non-native is far from straightforward. Just don't feel that growing non-native plants and gardening for wildlife don't mix. If you're careful, they most certainly can." After Monday, I'm sticking by that...for now!