Well as for this question: " Next, I'll list reasons (the ones that come to mind right now) for and against introducing invasive plants." For the ones you list, 3 is a pretty good one. If it is already here, and already in a heavily altered landscape that will never be natural, then it is alright to use. Number 6 is good, too-since humans have changed everything, these invasive plants have found a niche in the new environment we have created. Nature has a hard time existing where I live, 95% of the county is in intense agriculture, 80% is plowed field of corn and soybeans, so sometimes people's views might be different because what they see on daily basis. Now with high prices of land and commodity prices, even the naturalized species are being destroyed, leaving less room even for the more adaptable species of animals.

Greenthumbz, those are gorgeous pics! I've heard that there are a couple of trees that are not native to North America but are used by significant numbers of native insects. 1) Malus/Crabapples - native, hybrid, or exotic, Douglas Tallamy's book stated that the leaf chemistry is so similar that North american insects will use all species. This certainly bears true in my experience. I've got lots of crabs, a few specimens and a crazy wild thicket full of them in back,and they are bird magnets, not just for the fruits in the fall but for the nectar and insects in spring and summer. 2) Picea abies/Norway spruce - don't have any personal experience, but was told this by an ornithology student at Cornell who was doing a study on the subject

oops, wrong forum, meant for palms forum

This is such a good topic. There's so much debate of the definition of terms: native, weed, and invasive. And it varies from botanists to horticulturists to taxonomists to agrarians to... It really warrants discussion. While you may eventually find an equilibrium between an introduced species and its new habitat, it's doubtful that an equilibrium would establish between the introduced species and the native species it supplants (bad pun). So many microniches and urban and suburban borders make it more difficult for the spread of native plants, and much easier for the introduction of foreign ones. Each microhabitat in which a native species is 'successfully removed' represents a loss of genetic diversity within that particular species, and of course, the more limited your genetic material, the more vulnerable you are to disease and predators. As an example, if you are a plant species with a slow maturity and/or reproductive cycle like Maryland's native persimmon, living in a very specific environment (brackish swamp), and a well-adapted invasive, like the common reed (aka 'phragmites'), comes along--without intervention your resources are going to get used up and your population will have a difficult time recovering. I've heard arguments that this is just accelerated 'fittest of survival,' but as Springa7 mentions, our scale of international trade and potential for introduction of species is unprecedented. Researchers have found that islands are terrific models for this line of inquiry and there are several books on the subject. One of my favorites is Song of the Dodo: Island Biogeography in the Age of Extinction. It's not hardcore data, but more essay format. **In reply to Botanybob's comment that 'all noxious weeds are introduced,' it seems to depend on which group you're asking. I recently read that natives can be considered noxious--for instance, in a recently disturbed area. Cattails were given as an example. Got the info from this website on plant management in Florida wetlands: http://aquat1.ifas.ufl.edu/guide/invplant.html --Sara