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Native or non-native: which plants are best for insects?

Shrubby hare’s ear, Bupleurum fruticosum, is a top plant for hoverflies (André Karwath aka Aka (Own work) ‘CC-BY-SA-2.5 (www.creativecommons.org/licenses/by-sa/2.5)’, via Wikimedia Commons)
When, a couple of years ago, I wrote about non-native plants often being better for wildlife than native plants it prompted a lot of comments, for and against, and also private emails – mostly against, including some that were unexpectedly unpleasant.

Undeterred, I bring news of an article by Dr Ken Thompson in Britain’s Which? Gardening magazine, published by the impartial, non-profit Consumers’ Association (similar to Consumer Reports in the US) which says the same thing: “Recent research shows that non-native plants can be just as attractive to wildlife as native ones – if not more so.”

Ken Thompson, of the University of Sheffield, is a biologist with a special interest in the science of gardening. He’s examined recent research at the Social Insects Lab at the University of Sussex, and at the Royal Horticultural Society’s Plants for Bugs project and reports that “pollinating insects have no clear preference for the flowers of native plants”.

So we gardeners can rest easy. If we’re looking to attract insects and other wildlife to our gardens, garden plants are often better than native plants. And there seems to be no argument that, especially in densely populated areas, gardens make crucial contributions to the success of so many birds and insects

Borage, Borago officinalis, is the ultimate honeybee plant. Image So what to grow? To attract pollinators, Ken Thompson recommends these four plants:
Borage - “The ultimate honeybee plant” (left, click to enlarge)
Buddleia – “For butterflies, you still can’t beat buddleia, which is also used as a larval food plant by at least 19 different moths”. [Note: Buddleia is invasive in some parts of the USA, where only varieties that do not produce seed should be planted.]
Catmint – For bumblebees “for sheer attractiveness over a very long flowering season”
Shrubby hare’s ear (Bupleurum fruticosum) – For hoverflies, “a plant you’ve almost certainly never heard of”. (top)

So these are the first plants to try. And the number of hoverflies you’ll find on that bupleurum is amazing.

Ken Thompson’s article Native vs non-native plants: which are best for wildlife? appears in the June 2013 issue of Which? Gardening magazine. It is not available online.

You can subscribe to Which? Gardening here

You can check out books by Ken Thompson on amazon.co.uk

You can check out books by Ken Thompson on amazon.com


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Weeding the Web

Interesting. Wisley have had an area dedicated to growing native and non-native plants to gauge their attractiveness to insects (not sure if it's still there). When we visited a couple of years ago, mid-summer, it was very clear that the insects were far more interested in the native and northern hemisphere beds than in those growing southern hemisphere plants. (Mind you, we only went there once, so it might have been free take-away time at the Lavender Bar.)

About the seedless buddliea, if it doesn't grow seed, does it bother to produce much of what the insects want? It doesn't actually need to attract them, does it?

Cynthia, aka Gaia gardener

While insects will use almost any flower for nectaring, it's in eating the foliage that the big difference between the use of native and non-native plants is found. While Buddleia may have 19 different moth larvae that use its foliage as food in Britain, for example, here in the U.S. it is not used in that way at all.

Incidentally, most native plants have developed mechanisms to co-exist with the native insects that eat their foliage, thus maintaining a balance and doing serious harm to neither. Once you start introducing non-native insects into the equation, though, all bets are off.

I would suggest that, if you haven't, you read Douglas Tallamy's excellent book, Bringing Nature Home. It's one of the best summaries of the myriad of interconnections between native plants and animals that I've ever read.

Graham Rice

Yes, Weeding the Web, research for the RHS Plants For Bugs project that I mention includes monitoring the insect visitors to a range of plots planted with very specific plants - I'm in England at the moment so I'll go take a look. You can find out more at the project's webpage http://www.rhs.org.uk/Gardening/Sustainable-gardening/Plants-for-bugs and the scientist in charge blogs about the project at http://mygarden.rhs.org.uk/blogs/science__advice/default.aspx I'll add these links to my original post.

Graham Rice

Cynthia, you make a very good point. Extrapolating from one country to another, even one region to another, and offering advice for one region as good advice for another region, can be very misleading. For example, sticking with Buddleia davidii, in our Pennsylvania garden we've never seen a seedling in more than ten years and plants don't always make it through the winter. But that does not mean that it's not invasive elsewhere, and neither does it mean that because it IS invasive elsewhere that we should not plant it where we are.

I suppose my point is that there are far too many sweeping generalizations applied thoughtlessly and too many bold assumptions made.

And yes, Bringing Nature Home is a fascinating read.

coriander leaf

What i know is that native plants are better than nonnative plants for native insects...garden full of nonnative plants will not benefit local insects as much as one with native plants.

Alison Alexander

Ken Thompson ran the Biodiversity in Urban Gardens project at Sheffield University. Their study also found that natives are no better than non-natives for insects. One theory they proposed to explain this is that many of our non-native plants are from other land masses in the Northern Hemisphere which Britain was formerly connected to and that insects here today have not evolved significantly enough since to make plants closely related to our own natives inappropriate for feeding. I find this idea fascinating. If correct, it would explain also why many non-natives in the US are good for insects. More info on BUGS: http://www.bugs.group.shef.ac.uk/. Ken summarised the findings in a book called No Nettles Required. Sounds like I'm on a Ken T sales drive but no - am a former student of his and found him inspirational.

Graham Rice

Thanks, Alison. That's exactly the sort of reasoned thinking that is so often missing from this debate. So many people jump instantly to a natives good/non-natives bad prejudice that excludes impartial analysis. And that bias precludes consideration of so much good science. Drives me mad!

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