Thank you for this, Woody.

We have an interesting set of variables in the UK - although we are an island, we have been enthusiastically importing plants for 500 years - I was at my local botanics the other day, lurking round the 'chronological' beds and was startled to see the history of plant arrivals laid out so clearly - but then, as a maritime nation with imperial ambition, not so surprising. We also suffered late glaciation in the last ice-age which severely limited native diversity, certainly from mainland europe, so we basically squeezed a fraction of geological time into a few centuries of avid collecting...and finally, the gulf stream has blessed us with a mild and temperate nation - although we are somewhere on the same latitude as Moscow or southern Scandinavia (z5), the oceanic currents have lifted us into a forgiving z8. We are also very small (but crowded, with only 1/40 as much landmass as the US.

Consequently, while the debate regarding natives, invasives and ecological diversity has been elevated in the US, native plants have never really gained much traction here - not least because of the general paucity of garden-worthy contenders...so we are coming at this issue with entirely different assumptions and expectations...for which |I am glad since, although I lack formal scientific training, I do have eyes to see which are telling me that life is both tenacious and adaptable. Not having the vast and empty land masses in the UK, we have never really taken the issues of invasive plants to heart, apart from a small number of obvious contenders, most of them aquatic - Flora and I have often commented on the continental differences here and in the US - so we are coming at this question purely in terms of pollinators.

An example which chimes with my personal experience: I garden in the one tiny part of the UK which still hosts the swallowtail butterfly - for one reason or another, this butterfly has gone down an evolutionary dead-end of depending on one difficult and elusive food plant...which also only grows in this area of undisturbed waterways...and as such, they are rarer than hen's teeth - I have seen only one (this June) in my entire life...and yet, the continental swallowtail has a much wider range of caterpillar food plants (although still in the apiaceae family) and, as climate changes are afoot, we are seeing odd sightings of this warmer-blooded butterfly cousin...and so butterfly conservationists are quickly planting up more umbels since if the 2 species have a chance to meet, to breed or even, in extremis, our butterfly may be forced to adapt - LIFE WILL FIND A WAY. And not only do I enthusiastically grow fennel (one of the continental's favourite foods) I am also growing milkweed because you never know.

Conversely, in order to deal with one of our more troubling invasives, Japanese knotweed, plans have been afoot to bring in a particular variety of Japanese beetle which predates on this plant...and we are assured that as soon as the knotweed plants are completely eaten, the beetle will also die out. I am not reassured...although this is not THE japanese beetle of wanton wholesale plant destruction (we are told) I cannot help being sceptical that these 'biological controls' are simply going to lie down and vanish. Life is also tenacious.

It's interesting to read their lists, since almost everything they have listed as native, is not native in the U.S., and vice versa. Makes sense, when you think about it.

I hope similar research gets done in North America to see if the results are different here, given the different continental conditions here. I've read in several places that a possible explanation, for example, of the greater degree of red in fall leaf colors in North American trees and shrubs is potentially due to the relative ease of N-S spread of insect pests exposing North American plants to a wider variation in pests vs the E-W orientation of the European and Asian land masses. The chemicals that are evident in the red/orange leaf color apparently offer more insect protection than do those that cause the yellow fall leaf color that is supposedly more common in European trees. I don't know how true that is, but it does make me curious whether the results of a similar bug study here would differ or not.

Campanula - The UK is indeed 'the blessed isle' when it comes to garden conditions :-) It's an interesting contrast to the Avalon peninsula of the Canadian province of Newfoundland. The peninsula has the Gulf Stream running past its east coast, which offers some warmth on that side. But the Labrador Current on the west side brings icebergs from the arctic. The glaciers from the ice ages scraped all the soil off and dumped into the Atlantic (making the Grand Banks which, prior to over-fishing, was a phenomenally productive fishery...) NFLD's nickname - the Rock - is applied for a reason! :-) Soil is thin and growing conditions difficult - very different from the UK. But life does indeed find a way and there are lots of very interesting plants there - but an English style garden would be a struggle to maintain (although I'm sure there are people there who try for it....!)

I have been working hard for the past four years to develop a pollinator garden with native plants that bloom throughout the warm seasons and are foe rant of our weather, etc. etc. Frustratingly, by far the most reliable and attractive plant I have is the invasive annual Verbena boniarensis. It self seeds along the south edge of my yard right up against the road, where it grows in less than an inch of dusty sand on top of pavement in the blazing sun. Foliage is as green today as it was in late May and it has been blooming since mid-June, with no supplemental water. The pollinators all flock to it. They will take time out to visit each patch of native perennial, as they come into bloom briefly, but return to their precious Verbena once the perrenial's peak bloom has passed. Also, from an aesthetic point of view, the natives do look weedy and sickly as they head into winter mode. I try to leave most things up to provide seed for the small creatures and birds through the cold months. Plus, I benefit from their volunteer seedlings, as well.

So, I think non-native annuals are going to remain a staple in my pollinator garden. Diversity does have significant advantages. And I enjoy Zinnias and Tithonia.

Martha