the definition of a weed is a plant that doesnt belong in the spot that its in, so in essence introduced exotic species can be seen as a weed if its in the wrong spot. The main thing against them is that most of them over take in a bush setting and out competes the natives. although a lot of what he says about self sustaining ecosystems is probably true, somehow I think that natives are better as they are what grows well in the forest and brings the natural ecosystems to that area which is what a lot of people I know personally would prefer.

Most blackberry does that in spots and I am still in favour of getting rid of them and giving the natives a chance..

but then again I am pro native … :)

I think exotic species (invasive exotic species, not each and every exotic species) can be a problem for biodiversity… But I think the first problem wasn’t the exotic species, but man who altered the native environment.

When the Europeans arrived in America, they found an ecosystem that was inn equilibrium, but the plants in that ecosystem weren’t used to much disturbance of the soil. The colonists introduced other more intensive ways of cultivating the soil, and meanwhile, they introduced species that were more adapted to disturbed soil than the natives were, (That’s the reason we do have invasive exotic plants in Europe, but their number is much smaller: because agriculture is much older in Europe and Asia than it is in America and Australia, we have less plants that don’t tolerate a disturbed soil…)

I know about one invasive species whose eradication would probably lead to a return of an equilibrium all over the planet… Not within years, but at least within centuries… Yes, I do think that man is more of a threath to biodiversity than the exotic species that he introduced everywhere. We shouldn’t blame the invasive exotes, but the species that introduced them! (not only disturbance of the soil, but also climat changes can be blamed for the invasiveness of the invasives…)

I try to remove invasive exotes from my garden (e.g. Black cherry – Prunus serotina and Red Oak – Quercus ruber) and I try to have as many native species as possible in my garden.
But I know that scientific research has shown that the biodiversity in gardens with only ‘exotic species’ isn’t less than in gardens with only native species. (See http://www.bugs.group.shef.ac.uk/).

In America, the distinction between ‘native’ and ‘exotic’ is much clearer than in Europe…
In America natives are plants that grow there before the Europeans arrived.

In Europe, we also make a distinction between native, archeophyte and neophyte. The second kind of species have naturalized after their introduction by man before 1500, the latter only naturalized after their introduction after 1500.
This means that many species that really are an enrichment for our local flora aren’t truely native, but are introduced by man. And they are considered as a ‘valid’ part of our local flora.

(I have to rreturn to work, but there is even more to say about this…)

I don’t have the slightest care about invasive or non-native species… I am not able to go out to a field or a forest and conduct an investigation and identify any species that does not belong there and that is not an integral part of the ecosystem… I can only put the non-native label on a plant if I do a historical analysis: And since I don’t care about history, I am not able to care about invasive species.

I’m of the JL Hudson mindset all the way… Perhaps I’m cynical, but I think that concern about native species exists primarily as a marketing tool to sell more herbicides and pesticides.

Nature doesn’t like void space and will use "weed’s to fill the hole…what most people consider "weed’s are valued by others as part of an ecosystem and usually have some benefit but when modern aesthetic values (nice neatly design planting rows, bare soil or mulch in-between, chemically treated mono-culture manicured green yards) are the lens looking through many things can be considered weeds. Mother nature doesn’t like bare ground and human cultivated ground, she treats it like a wound and will send out pioneer species, most commonly considered weeds, to restore and heal human broken ground. If you have species plants growing that you are not fond of listen and look closely, chances are something is out of balance.

Well this is certainly an interesting debate. My quarter in the slot machine and it comes up with…

There are certain issues with introducing or innocently bringing in plant material for your own garden from another country or what we are calling invasives. Some invasives become so rampant they take over the biodiversity of wetlands such as purple loosestrife. The problem where I live is that the wetlands contain a certain balance of plant material that support other forms of life – or biodiversity. When loosestrife chokes out these plants it changes the biodiversity and threatens the chain of life. I myself, like my friends the animals and plants. I like the look of purple loosestrife too – but it does much more harm than good here. AND the government has spent lots and lots and lots of tax payers money to get rid of it.

I know we are just a large living breathing entity called life. It is overwhelming to think about the true impact that the human species has had on the earth and the responsibility is not something everyone can get their heads around. It’s too bad though. Because not educating yourself about what impact your footsteps create or what your actions promote can lead to generational illogical harmful choices. It’s not everyone’s “thing” though. So I battle my own judgment and try to think of ways to educate or draw in that one piece that will click in for people.

Native species do best in the climate and conditions in which are native to you. They’ve adapted based on our weather, soil, and air conditions. Permaculture is a philosophy to bring in and utilize our native species to grow i.e edible forest and adaptive methods to grow our plant material. Even our veggies. Now, veggies by all rights are mostly controlled foreign species that are not invasive – well maybe that currant tomato I have is… but that’s another story. So in order to be thoughtful considerate caretakers we should become educated and mindful of our daily actions. Anything less is not an option we can afford.

@anelson, By the way – I don’t consider foxglove invasive – therefore I don’t consider it an issue with taking over, do you? It’s gorgeous to boot and a great source of medicinal value.

My tiny 2 cents worth is that the word ‘invasive’ is key, whether it be ‘exotic’ or not. Like others above have said, if it doesn’t play well with others, then don’t plant it even if you think you can control it in your garden. Others may not appreciate your taste when it travels.

I agree with what AnneTanne said in her first post about humans being at the origin of this problem and I agree with JosephsGarden on Hudson’s philosophy. More harm is bestowed on the planet when we use profit producing chemicals to undo what mankind had caused in the first place.
This is not to say that I don’t succumb to bitching and moaning when my little piece of paradise is affected.