What I am hoping for is 1) a better definition of just exactly what invasives are, 2) a list of positions held on both sides of the invasives issue, and 3) some analysis of these positions. I would add 4) conclusions about which viewpoint makes the most sense, but I don't think we are really going to solve this complex issue with this one discussion.
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I'll start with one possible definition of invasive. And, BTW, in this thread we should assume we are talking about plants that have the potential to strongly influence the ecosystem, not just aggressive plants.

Invasive - a non-native species, introduced into an ecosystem, whose aggressive proliferation causes significant displacement or harm to native species. Invasives are frequently characterized by rapid reproduction, high dispersal rates, wide adaptability, and lacking sufficient competitors or predators.

Hopefully others can add other definitions or suggest possible changes to the definition above.
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Next, I'll list reasons (the ones that come to mind right now) for and against introducing native plants.

For:

1. Some intrinsic value of the plant outweighs the potential harm.
2. Some intrinsic value, to humans, outweighs the potential harm to other species.
3. Since the species has already been introduced, adding more individuals won't make much difference in the long-run.
4. Everyone else is planting it, so why shouldn't I?
5. Since we can't completely predict what the final result of adding an invasive species will be, we can't be sure it's a bad thing.
6. The ecosystem will eventually adapt to the new species, so the introduction of an invasive is only a temporary bump in the road.
7. Only the strongest species deserve to live.
8. Doubt concerning a plant's invasive potential makes it OK to ignore or deny reports and current data.

Against:

1. Adding invasive species is the biological equivalent of littering, except with exponentially reproducing rubbish.
2. Invasives cost us many hundreds of billions of dollars per year in lost productivity, management costs, etc...not to mention the ecological costs.
3. Species, ecosystems, and environments may be completely lost due to the introduction of invasive species.
4. As thinking and reasoning beings, it's our duty to limit the damage we do to the environment.
5. Invasives sometimes lead to monocultures, which are boring, unhealthy, and unnatural.
6. Invasives can invade your personal garden or landscape and result in a significant increase in required maintenance.

Most of us can hopefully see some problems with some of the ideas above. Let's discuss these in a friendly and fact-based conversation.

I hope others will add further reasons for either side of the debate. I think these reasons may be key to our understanding of the issue.
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I'll leave the analysis for others for now. I'm sure I'll probably add more during the discussion, but this post is already getting pretty long.

The more often accepted definitions eliminate this potential label for natives, even in those cases. But, we could also discuss this subtopic further.

I prefer to grow a preponderance of native plants, but think it's okay to grow exotics, as long as they have been proven to be more or less non-invasive. For examples, Lilacs have been growing in North American for centuries and show no tendency to take over the countryside. And they are beautiful and provide early nectar for butterflies and hummingbirds. Any exotic plants that have shown to be invasive in a particular region should be prohibited, and those that are invasive in other regions should be closely watched - they could be "coming to a neighborhood near you".

The vast majority of exotics aren't invasive. I think many people get that mixed up, and that sometimes causes people to misunderstand the whole concept.

IMO, the only approach that will work is to evaluate each and every exotic plant species individually. For an example, in my part of the world, both common and glossy buckthorn are truly damaging to the woodlands they invade. The reasons have everything to do with their ability to make life there impossible for numerous native species. Yet in exactly the same types of habitat, dame's rocket-Hesperis-is also present. Companies that exist to promote "native plant communities" have Dame's rocket on their lists of plants which must be eliminated. I always wonder what the urgency is in this one case: I mean, what would be growing there if the dame's rocket was eliminated? More buckthorn? Garlic mustard? Likewise with wild parsnip, which truly is running rampant, especially in roadside ditches. Large dollars have been devoted to programs to wipe this plant out. And again, this leaves me wondering-are we trying to make more habitat for reed canary grass-another invasive species?

Obviously, I've thought about this often. My job involves such issues. Meanwhile, some of my very favorite plants are showing up on this state's invasive species lists, things like Norway spruce(!) which escapes only sporadically and which, presumably, is crowding out what-native white spruce? I would not buy that idea. Yet it's out there, and very nice trees are being taken down.

Finally-for now-the thought that species which are native to a given area are sometimes listed as invasive tells me that the managers of said properties have a constricted view of what natural succession is. Most typically, this comes up in prairie management. Yes, there were prairies in this state, mostly in the S. half. It is considered true that even these "natural plant communities" existed largely due to the activities of man, in this case, Native Americans, who would burn certain areas to further their goals. But somehow, it has caught on as the de facto native plant community in regions of the state where it never amounted to much. Forests are the original plant community of most of this state, yet when someone is working to develop a prairie community, such natives as aspen or white pine are viewed as invasive enemies and are eliminated. That's just so wrong in my view. Any prairies that existed in this region would have been temporary features of the landscape following a disturbance of some type. To attempt to perpetuate such plant communities misses the fact that such are always in flux.

Of course, wouldn't you know it, a large part of my work involves establishing and maintaining prairies! They're cool and all, but the whole thing is just so misguided.

Next...............+oM

In my original post, please replace

Next, I'll list reasons (the ones that come to mind right now) for and against introducing native plants.

with

Next, I'll list reasons (the ones that come to mind right now) for and against introducing invasive plants.

Your second point (about the lack of understanding even among some that should know better) is one that concerns me a lot. I think the type of mis-information you point to is one possible reason some people may take the whole concept with a grain of salt. I definitely think there are those that have a deep understanding of this subject, but obviously there's the other side of that coin, too. This lack of understanding may be a kind of unintentional sabotage from the inside for the "anti-invasives" group.

"I'll start with one possible definition of invasive. And, BTW, in this thread we should assume we are talking about plants that have the potential to strongly influence the ecosystem, not just aggressive plants.

Invasive - a non-native species, introduced into an ecosystem, whose aggressive proliferation causes significant displacement or harm to native species. Invasives are frequently characterized by rapid reproduction, high dispersal rates, wide adaptability, and lacking sufficient competitors or predators."

Here's where the most problems will arise in this discussion, in my opinion. To propose that there are multiple possible definitions of the term invasive - well, that just invites impossibility of any consensus. It would make sense to start from a point of an agreed-upon definition (choose an authority) and go from there.

I'd also invite those unfamiliar with some of the good work done in the last couple decades to avail themselves of the good information out there.

I've attached a link or two with which I am intimately familiar, from a highly diverse and collaborative process.

To respond to comments above on invasive qualities of native plants: I suppose the assumption is "native to North America" means native anywhere (or allowance of use) anywhere on the continent. Some plants that could likely be lumped into this subset would include Robinia pseudoacacia, Maclura pomifera, and Typha latifolia. These plants can behave just like some of the nonnative exotic pest plants that most of us easily abhor.

So would you like to debate the introduction of non-natives? ....because the introduction of some species such as kudzu and gypsy moths were actually the result of someone thinking it was a good idea at the time.

But still, the proposed direction is not at all what I had in mind. The vast majority of non-natives appear to have very little impact on ecosystems, and I doubt many of us would consider strictly limiting ourselves to only natives. That would surely be a loosing battle, even if we were to hold that value.

That does bring up one other reason that we could kind of put in the reasons "for" column. We could add that...
Some invasives are unintentionally introduced because of lack of sufficient study of their potential impact. (I'm not sure people would give that as a reason for their current action though.)

Also, by now I must have read this about one thousand times, about how native plants are more adapted to their environments, need less water, fertilizer, blah blah. It seems beyond obvious that these same attributes are precisely why some exotics are flourishing. Also, the notion that only native species provide benefit for wildlife is equally ignorant. Is it not precisely the suitability of buckthorn fruits as food for birds that is responsible for its widespread dissemination? Yes it is.

I can only consider each case on its own merits. Any purist, dogmatic embrace of all natives all the time, or its opposite, a cavalier approach in which no harm is ever considered by the introduction of a non native plant, are both equally useless to me.

I hope Pine resin chimes in on this thread. In Great Britain, vast acreages have been planted to non-native conifers, especially those from the Pacific Northwest of the US. Predictably, there seems to be a huge backlash against this practice, this despite the fact that prior to the establishment of these plantations, no trees were present there, and also, these species have done marvelously well in their new homes. I consider that a positive development, an example where man and nature are truly working to create something better than what would have otherwise been. I consider my own use of Norway spruce and hybrid larch in my own tree farm to be likewise enhancing the richness and beauty of the great native species already present.

And what are we to make of the fact that some very good native species are gone from the original landscape, because of introduced pests or other maladies? Does it not behoove us to take a stab at finding a suitable replacement for these species from the list of plants that originated elsewhere? I think so. Consider the Eastern hemlock. Fortunately, where I live, the adelgid has not yet showed up, so we still have this marvelous tree in our forests. But further back east, it's gone, probably for good. Is it impossible to thing that perhaps Norway spruce, just to use that example, could somewhat fill this niche in the eastern forests? Not exactly, but close enough to fill some gap.

I think ultimately, with pests being moved around the planet like never before, we will need to move beyond purist thinking to a more creative approach, in which select non-native plants are used to add, not detract from the landscape.

Finally, beyond trying to decide what people should or should not plant, I would prefer to see more effort put towards saving intact native plant communities from "development". So much effort is spent trying to grow native plants on soils that have been altered, often beyond recognition, while right next door, another woodlot is being cleared for a new parking lot.

And we haven't even gotten yet to a discussion of what really constitutes "native", in genetic terms. Is a species that is found natively in your area still native if its genetic makeup is from a location hundreds of miles form your spot? And could we be doing more damage by introducing such plants into our region, by changing the genetics of the existing populations over time, than we do when we bring in completely non-native species? It gets complex pretty fast. That too is why I take a case by case approach to such matters.

+oM

In Virginia, it is not invasive species that crowd out native forests. It is property development. People are clearing out forests to give space for property development, roads, highways, Walmart and of course farming. People want money; they are not thinking about protecting native species. People like you are slightly different, i think ideology play a row in your position :-)

Anyway, Brandon's definition of invasive species is the pure scientific one, but I think in some contexts the definition needs to be enhanced and the scope of the problem widened. The US doesn't spend billions of $$ to fight invasive species each year because biodiversity is threatened and some rare native plant or insect is about to go extinct, but because human economic interests or quality of life are threatened.

Apparently an invasive plant species becomes a "noxious weed" when it starts to threaten human agriculture or livestock, and that native species can be noxious weeds too, but I'm still a little unclear on this distinction.

In the south, good examples are Kudzu, Chinese privet and English ivy (there are others, of course). Kudzu does it by growing as a massive vine that smothers all things it encounters. English ivy is similar, but slower to do it's work. Chinese privet spreads primarily by fruit; it is successful in it's ability to grow virtually anywhere (sun, shade, wet, dry) and create dense thickets of vegetation, preventing the seedlings of other plants from thriving to maturity.

There are regionally native plants that have the ability to naturalize in new areas. Southern magnolia (Magnolia grandiflora), for example, is a coastal plain native that is seeding into natural areas in the piedmont, sometimes in a heavy way.

While I agree that man is the most destructive species overall, what we are talking here is plants, not all species on the Earth.

What is truly sad is that when man does set aside areas for conservation - often those areas become invaded by invasive plants due to lack of knowledge and manpower to control them there. So what we have attempted to protect becomes invaded.

Why does controlling invasive plants make a difference? Because the diminished populations of native plants have a reduced capacity to support their local ecosystems. Reduce the populations of native plants and you will also reduce the dependent populations of insects, pollinators, birds, and the fauna that depend on those things.

For example, allowing autumn olive to take over a sunny roadside/woodland edge may provide a few more berries for birds, but it provides nothing for the insects that relied on the native vegetation the olive out-competed. Native insects don't eat autumn olive foliage. Eventually the reduced insect population will cause the birds to produce fewer chicks because there are not enough insects to feed them.

So while some might argue that allowing these non-natives to do what they want because it increases bio-diversity, in the end, it reduces bio-diversity because other plant species diminish.

Again, keep in mind that we are discussing non-native invasive plants, not the well behaved non-native plants that are not on invasive lists. Always check regional lists that have been compiled by experts - you cannot rely on personal experience in the garden to decide if something is invasive or not. You can't always SEE "invasive" behavior when fruit/seeds are involved in the invasive process. Remember it is "wind, water and wildlife" that distribute fruit/seeds.

I would note that while this discussion seems to be mainly about invasive plants, the term certainly includes other organisms as well. I think it's harder for people to argue that an exotic insect or pathogen that eliminates native tree species - or for that matter, an exotic mosquito that spreads Dengue fever to humans - is anything but a bad thing. But it's appropriate to focus on plants in this discussion, because the majority of now-invasive plants were originally introduced and cultivated intentionally, and we're bringing in more exotic species all the time.

While there's no doubt that invasive plants can have very negative impacts, I agree with wisconsintom (as we've discussed recently) that there's a tendency among some to label any exotic, naturalized species as "invasive" even if its potential to cause problems has not been demonstrated. I think that this can lead to a waste of resources that could be used to focus on the real problems.

However, complicating that issue is the "lag-log" problem. Typically, there's a "lag" period after an exotic species becomes naturalized, where it persists in the environment at low, non-problematic levels, followed by a rapid (logarithmic) growth phase where the population spreads more aggressively (this is the classic sigmoid curve of population growth). In some cases, that "lag" period can be quite long, on the order of decades. It can be very difficult to tell whether a newly-naturalized plant is inherently non-problematic, or just hasn't become a problem... yet. And by the time it can be demonstrated that an exotic is causing problems, it's often well-established and no longer feasible to eradicate. These issues would be points in favor of a "guilty until proven innocent" approach.

I would also like to support comments from wisconsintom and others that human of development (and other effects, such as fire exclusion) of natural areas has more of an impact on them than invasive plants. However, I also think that these issues actually complement each other. As natural areas become increasingly fragmented, the integrity of the remaining native systems becomes all the more important, as wildlife habitat and serving other ecosystem functions. These remaining natural areas also become increasingly under pressure from the invasive plants that we spread around, as we break them up and move in next to them.

You have Mr/Mrs homeowner who go to a nursery not knowing if a plant is invasive and quite frankly probably doesn't know what an invasive is.

There are multiple nurseries around here that continue to promote and aggressively sell invasives because they are easy to grow, fast to grow and help their bottomline.

I wish they would take some responsibility to at least educate homeowners if they want to promote these plants.

Same goes for plants that have fallen out of favor due to extreme susceptibility to diseases. Yet its easy to grow, fast to grow so it helps their bottomline.

Our efforts to remove invasive plant species should be well-organized, and it bothers me that time would be wasted removing Norway Spruce and not Glossy buckthorn - especially because I've read that Norway Spruce (along with crabapples) are one of the few non-native species that appears to support a significant number of native Lepidoptera.

There are some invasive plants that appear to be gentle spreaders, like Queen Anne's lace (Daucus carota) and Hesperis matronalis. They no doubt are occupying a little habitat where natives could be growing, and I wouldn't encourage them, but appear to be lower priority.

In the eradication of invasive plants on my own lot, which has been an ongoing and by no means perfect effort for 7 years now, I tried to prioritize and remove the worst and largest offenders first, like Oriental bittersweet (Celastrus orbiculatus) and Glossy buckthorn (Frangula alnus). I also try to remove all fruiting plants each year, to prevent additional spread.

Just last week I was browsing thru the Gardens Alive catalog and they were selling Burning Bush seedlings - which "could not be shipped to MA, NH, etc". Wow, I used to think Gardens Alive was a environmentally conscious company but now I wonder.

It also makes me crazy to see posters on the Seed Exchange forum offering stuff like Burning bush seeds for trade. Gardeners are part of the problem too!

The natural world is intrinsically linked. It is not scientific to isolate the topic to plants only. If one wants to link the decline of a certain native plant and/or animal to a specific invasive species, then a study should be conducted to find out whether this is true or not. Speculation is a big no no.

I agree, but as I pointed out, by the time such an impact can be demonstrated, it may be too late for effective eradication. The question becomes where the burden of evidence should lie. In most current state and federal laws, they take an "innocent until proven guilty" approach, with demonstrated baddies placed on a prohibited list. But using that method, one waits until the cats are out of the bag (and reproducing in the wild) before trying to catch them. Prevention would be a much more effective (and cost-effective) approach.

In Virginia, it is not invasive species that crowd out native forests. It is property development.

Again, it is both. The effects of invasive plants magnify the effects of property development on the remaining green space.

The Native plants are adjusting. For example, the Dutch Elm disease cannot kill an American Elm before it produces seeds. So, over time, American Elm is able to overcome this. It may take millions of year. It is humans who do not want to see sickly plants and thus humans remove the American Elms.

The American elms may or may not eventually adapt and develop natural resistance to DED in the population, but they may not. It does not appear that American chestnut is likely to recover without human assistance, and the prospects look similarly bad for our native species of ash, hemlock, and Persea.

But that said, I'm going to argue the less popular (on this forum at least) pro-invasive point. As long as no one verbally attacks my children or personal hygiene I think my feeling will remain intact. Plus it's winter and I'm a little bored until seed starting begins.

Invasives are here and we need to get over it. Destroying healthy ecosystems and replanting them to what they might have been(who really knows what a pre-European N America landscape looked like) is like telling all non-native americans to leave and go back to where they came from. Actually why stop there? Why not call the Bering Straight land bridge a big mistake and have all native americans go back to Russia. Then we can do some genetic engineering and bring back the mega fauna of the ice age!

The world, for as stable as we like to think it is, is constantly in flux. Ecosystems shift, new species evolve, adapt and 'improve' on what was there. I may be biased but I have no problem with homo sapiens over running the world and pushing the neanderthals to extinction. History is written by the winners, not the losers. So give it a couple decades and 'invasive introduced' becomes the new stable. It's just a modern version of cleaning house and getting rid of all the stagant gene pools in favor of a more adaptable one. For those bleeding hearts out there, put your time and effort into putting a museum of plants together... oh no wait, it's called a botanical garden, and we already have those and have filled them with just about anything out there that's of any interest or worth... and I think that's plenty enough. The rest of the stuff out there should be sink or swim.... or as other people call it "nature" and "evolution".

Here's another argument. Restoring ecosystems is never going to happen. Physically and financially the task is beyond us. From soil structure (agriculture and introduced earthworms) to climate change (another totally natural progression... ouch that actually hurts for me to put that in print) to invasive plants to invasive insects and animals, to new pollution levels and ph levels..... There is no chance. We can waste our time or we can adapt.

How's that?
Oh and why should nursery owners be held responsible. Where there is a maket and a demand, why should they ignore that opportunity and let someone else make the money? If a plant does act invasively, a homeowner is just as likely to cross the street with a shovel and dig up some purple loostrife as he is to go to a nursery and buy a potful. If there a millions in the woodlands around your home what difference will one more plant make growing in your perennial bed.

kato "Soylent Green"_b

I have seen at least one definition of invasive that took the above idea into account, and I really wanted to include it in the original post, but was unable to locate it. I think it's important to realize that the problem is not just with the particular plant, but with the ability of the ecosystem to deal with the plant and bring things back into balance.

From that link (pp. 11-12 of the Proceedings), I've excised a presentation by Dr. John Randall which gives the best summary definition I know. It captures those things about invasives species that brandon7 may be alluding to.

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The Environmental Impacts of Invasive Plants
John Randall, The Nature Conservancy

"E.O. Wilson once said: "on a global basis, the two great destroyers of biodiversity are, first habitat destruction and, second invasion by exotic species". Dr. Wilson's comment reminds us, along with many other reasons, of the need for better understanding the impacts of invasive plants in natural areas. These impacts can be grouped under two broad categories:

1) ecosystem level impacts; and,
2) community and population level impacts. In some cases, invasive plants have little impact on natural areas. In others, they have positive impacts.

Invasive plants can affect the ecosystem processes that determine much about the whole suite of animals and plants that can survive in a system in at least several key ways. First, they can alter the rate and intensity of wildfires. The best known example of this occurs when cheat grass (Bromus tectorum) invades areas dominated by native sagebrush (Artemisia spp.) and other shrubs, promoting frequent fires which kill the shrubs. Along the Gulf coast, the invasive cogon grass (Imperata cyclindrica) invades fire-adapted longleaf pine wire-grass communities where it increases the intensity of fires to a level that the native tree seedlings cannot survive.

Certain invasive plants can also alter an ecosystem's hydrology by changing the location of the water table. For example, in South Florida's everglades, the invasive Australian tree Melaleuca quinquenervia, has moved into parts of the "river of grass" and changed these to forested swamp, lowering the water table in the process.

Invasive plants can also alter rates of sedimentation and soil erosion within ecosystems, depending on the plant type. For example, spotted knapweed (Centaurea maculosa) moves into grasslands in the inland northwest and other parts of the country where it displaces the native bunchgrasses and herbs, but its root systems are far simpler and do not slow runoff from rainstorms in the same way. Thus runoff and consequent erosion from invaded hillsides is far greater, and sediment loads in salmon streams far higher.

Certain invasive plants can also alter soil chemistry and nutrient cycles. For example, some nitrogen fixing species like Myrica faya have invaded systems like Hawaiian forests and shrublands that had few or no native nitrogen fixers and sharply altered nitrogen chemistry and cycling there. Even the familiar Japanese barberry (Berberis thunbergii) can alter soil calcium levels and pH.

Invasive plants can also affect plant communities and their population levels. One important effect of this type is alteration of vegetation structure, which kudzu (Pueraria lobata) is famous for. Kudzu grows up and over forest trees, covering them with a dense blanket of leaves, which is sometimes so thick that the trees supporting it no longer get enough light to survive. Invasive plants can cause changes in the composition of the species of plants, animals, fungi and other microbes in the areas they invade by displacing native plants that native animals and other organisms need for food and shelter. For example, invasive honeysuckles (Lonicera spp.) move into forest understories in the east and Midwest where they can completely dominate the shrub layer and displace native species. Invaders like this compete with and deprive other plants for key resources, such as water, light, nutrients and space. Invasive plants negatively impact native animals, ranging from birds and mammals to insects by pushing out native plant species the animals depend on for survival. Some invaders also promote other non-native plant invaders, reduce recruitment of native species (e.g. Norway Maple [Acer platanoides] vs. the native Sugar Maple [Acer saccharum]) or hybridize with native species (e.g., on the west coast the non-native Atlantic saltmarsh cordgrass (Spartina alterniflora) hybridizes and threatens to swamp out the native Spartina foliosa and in Florida the invasive Lantana camara may hybridize with the native Lantana depressa.

Invasive plants can have such a wide variety of impacts on so many native species, biological processes and physical processes, but in some cases no harmful impacts have been detected from invading plants, particularly those that never become abundant. Because of this and because the time and resources required to prevent or control and invasion can be high, it is vital for conservation workers to first determine what their conservation goals and objectives are in a given area or for a given project. They should be able to state which species, communities and/or ecosystem processes they are protecting and managing for. Once this has been done, they should
determine whether any of the invading plants in or near the area are known or thought to be capable of negatively impacting the species and processes targeted for protection. Information on the impacts - or lack thereof - of invading plants is thus vital for conservation land managers who need to make important decisions about how to allocate the limited time and money they have."

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The significant and relatively sudden alterations/effects to the environment/ecosystem around them - not just the presence of the plants - is (to me) the separating feature that constitutes invasiveness.

Also, I am well aware of the web of life supported by native plant communities. I wasn't arguing against that at all when I said we need to honestly evaluate the effects of the proliferation of one or another exotic species. So autumn olive is able to provide some food for some birds perhaps, but that in no way indicates that it is on my okay list. I regularly remove both it and Russian olive from our areas which I manage. I regard such plants as junk.

Now for an admission: I like purple loosestrife. It honestly pains me to have to eradicate it from our ponds and channels. But the damage caused by this plant is well documented.

Here's another: A state forest near me has a large amount of Lake Michigan beach. Formerly, much of the plant community on this site's sand dunes was dominated by blue lyme grass-Leymus arenarius. To put it simply, the effect was stunningly beautiful. Now of course, the managers have initiated an eradication program. The sand dune community is, in my opinion, much the poorer for it. But I will readily admit this is just an aesthetic opinion. I simply liked it better when that grass was still prominent. Will other native insects, etc. now do better because that species is gone? I don't know. I just know that previously, when climbing up the sandy trail to the point where the full expanse of beach could be observed, it looked a lot cooler when the blue lyme was still there.

Much the same with my Norway spruce. This spruce outgrows all of our native versions here. I think it adds to the aesthetic aspects of the places where it grows. Additionally, from the standpoint of commodity production, this spruce is more valuable than any of the native spruce in our area, growing both faster and larger. If it could be proved to me that somehow, the presence of this tree was causing harm to the overall environment, I would adjust my opinion accordingly. But I do not expect such proof to be forthcoming. Incidentally, the land where I have planted Norway spruce and hybrid larch (And native red and white pines and N. white cedar-all natives) was an alfalfa field previously. Now were I asked to weigh in on the conversion of a northern mixed hardwood/conifer stand to all Norway spruce, well, that's a different matter. But when used to "capture" some new land for forestry, I consider it ideal.

Ultimately, it comes down to 'what do we want". I would not care to see acre after acre of common buckthorn/Russian olive forest. So those would be targeted under my control. But if I saw an 80 year old stand of Scots pine, still growing and doing well, it would be hard to convince me that eradication would be the answer. But this too is going on in my area.

+oM

You have put a very large finger on one of the most difficult aspects of eliminating invasives: anthropological. We like what they look like, or we like what they do - despite the known overwhelming negative consequences.

If you think purple loosestrife is a nice bloomer, or the blue lyme grass offers wonderful colorful textural effects - imagine convincing Ohio River valley residents that Lonicera maackii ought to go away when it is in the prime fruiting season. The density of glistening red spheres rivals all comers - AND FOR FREE.

Of course, there's nothing else left - but they can't see the forest for the honeysuckle anyway.

And your point about the honeysuckle is spot-on. To move forward wisely in this realm, we need to account for as many aspects of a given species' impacts as possible. That takes research and research takes time and money, both of which are scarce right now.

BTW, isn't there some society dedicated to pretty much the exact thing I'm talking about-the need for a nuanced approach to plant community dynamics? I seem to recall something existing along those lines but it escapes me at present. Something about "beyond native" or some such in its title?

+oMdude

Comment regarding this sentence from the excellent info that viburnumvalley posted:

"Along the Gulf coast, the invasive cogon grass (Imperata cyclindrica) invades fire-adapted longleaf pine wire-grass communities where it increases the intensity of fires to a level that the native tree seedlings cannot survive."

It's actually not just the seedlings - even mature, fully-grown longleaf pine trees (a very fire-adapted species) can be killed by a cogongrass fire. I've seen it happen on our State Forests, even where a prescribed fire just runs through a cogongrass patch - lime-green grass sprouting back below, pines dying above. Cogongrass burns 15-20 degrees Celsius hotter than a regular understory fire, and it'll burn when green as well as brown.

We've got more than our share of invasive plants in FL, and Cogongrass is near the top of the list for the problems it causes, both for native ecosystems and for people.

So how much effort and resources are you willing to put into controlling invasives? Again, if they are just altering a few ecosystems is it really worth it to spend millions in a futile control plan that just saves a couple pine trees? If an independent conservation group wants to spend a ton of money and create an ecological island in an ocean of invasives, well good for them. It will be a nice ecosystem museum. Just don't waste my money doing it.

biodiversity. Big deal. The more exotics we introduce the more diverse our new systems become and the process comes full circle. If you feel bad about losing a few species along the way then maybe a proactive plan is to start shipping them around the world and maybe a couple will become the scourge of some other part of the world.

I hear some species such as monarch butterflies and canada geese are doing well abroad, maybe we can step his up.

I'm off to see if I can get a copy of Soylent green.....

I am intrigued however by that which you hint at at the tail end of your post-that some N. American species are naturalizing in other parts of the world. In the long view, this could just turn out to be a good thing. We simply don't know. If these species adapt and thrive, only to degrade the outcome for species that already exist there, it will be a net loss. On the other hand, if they are able to do so without crowding out or somehow limiting the opportunities for the native species in that part of the world, then it is a net gain. The problem is, we have only very limited means of predetermining this.

+oM

Maybe buckthorn wouldn't be as big a problem without the proliferation of introduced earthworm species. The link I previously referenced talks about the reduction of leaf litter and the elimination of the duff that most native woodland plants are adapted to in North America. Maybe we should focus on eliminating invasive worms first before making the buckthorn a scapegoat. A fertile forest floor of earthworm droppings is practically a prepared seedbed for buckthorn.... but not for lady slippers.

Maybe some kind of worm fence can keep them at bay... similar to the electric fences keeping grass carp out of the great lakes.

Invasive plants aren't usually confined to a "few ecosystems". One characteristic that's near universal for invasives is that they easily spread over vast regions and effect many many ecosystems. In unusual cases, when they are somehow limited to only a few areas, they are of much less concern to most of us and would probably be considered special cases for the sake of this discussion.

Another thing that I think many may overlook is the huge cost that invasives cost us no matter what we do. Ignoring them may be an option in some cases (Tom makes some good points related to that aspect), but they frequently have a large economic impact, either directly or indirectly, whether we like it or not. Currently, invasives are costing us hundreds of billions of dollars per year. Maybe we could make systemic changes in the way we live that could change that some, or allocate portions of the money differently, but ignoring the costs or wishing "they" didn't use "our" money is not reasonable. We are stuck with either much of the associated cost, or, making some major changes in the way we depend on the environment.

Not to mention that it increases the likelihood and intensity of wildfires that could threaten human lives and property. I lived for a few years in a part of Florida (Silver Springs Shores, outside of Ocala) where cogongrass reigns supreme. It grows not just in the natural areas, but in all the powerline right of ways, all the roadsides, and right up into people's yards and around their homes. The fire hazard still makes me shudder.

Even if you take the nihilist perspective with regard to ecosystems, there are many reasons to care about invasive species because of the problems they can directly and indirectly cause for us humans.

All this talk of invasives makes me want to go out and roundup a patch of garlic mustard..... oh no wait. The consistent use of roundup for the last 30 years has lead to the natural evolution of weeds that don't die after being sprayed. Bummer. So now the invasives don't have to come from foreign soils, we can breed our own!

What's going to happen when birds eat the seeds of invasives planted in a yard in the center of a city?

Now, what's the chances of a bird making it out of the city with a seed are?

There are trees in the middle of deserts. They are there because of birds. Many birds migrate. The reason the seeds usually die is because the new area is too hot or too cold. With invasive species they'll grow almost anywhere.

I'm so glad that, so far at least, everyone has stuck to the subject and not gone personal. It's sometimes hard with topics like this where feelings can be quite strong, but you all are doing a good job!

The aspect that I think we're still in need of more input about is what people that choose to plant invasives use to "excuse" their action (assuming they even see a need to do so).

Table 1. Some trans-Atlantic migration of avian species from Eurasia to the eastern United States
Documentation of exposure
Species Possible mode(s) of entry to West Nile virus
Cory's Shearwater, Calonectris diomedea Vagrant (33)
Manx Shearwater, Puffinus puffinus Vagrant (33)
Wilson's Storm-Petrel, Oceanites oceanicus Vagrant (33)
Band-rumped Storm-Petrel, Oceanodroma castro Vagrant (33)
Northern Gannet, Morus bassanus Vagrant (33)
Gray Heron, Ardea cinerea Vagrant (33) 34
Little Egret, Egretta garzetta Vagrant (33)
Cattle Egret, Bubulcus ibis Vagrant (33) 35
Greylag Goose (domestic), Anser anser Pet and domestic bird trade 18
Falcated Duck, Anas falcata Pet trade, zoos, vagrant (33)
Eurasian Wigeon, Anas penelope Migration (32), pet trade, zoos
Mallard (domestic), Anas platyrhynchos Pet and domestic bird trade 18,24
Garganey, Anas querquedula Migration (32), pet trade, zoos
Green-winged Teal, Anas crecca Migration (32)
Tufted Duck, Aythya fuligula Migration (32)
Eurasian Kestrel, Falco tinnunculus Vagrant (33) 18,36
Jungle Fowl (domestic), Gallus gallus Domestic bird trade 18,35
Quail, Coturnix coturnix Domestic bird trade 36
Northern Lapwing, Vanellus vanellus Vagrant (33) 22
Wood Sandpiper, Tringa glareola Vagrant (33) 36
Little Stint, Calidris minuta Vagrant (33) 36
Curlew Sandpiper, Calidris ferruginea Vagrant (33)
Ruff, Philomachus pugnax Migration (33)
Little Gull, Larus minutus Migration (33)
Black-headed Gull, Larus ridibundus Migration (33) 22
Black-tailed Gull, Larus crassirostris Vagrant (33)
Yellow-legged Gull, Larus cachinnans Vagrant (33)
Common Tern, Sterna hirundo Vagrant (37)
Rock Dove (domestic), Columba livia Pet trade 18,24,38
Oriental Turtle-Dove, Streptopelia orientalis Pet trade
European Turtle-Dove, Streptopelia turtur Pet trade 16,22,35
Eurasian Collared-Dove, Streptopelia decaocto Pet trade 35

So, snasxs, are you saying this is true for you? What "camp" are you in? The "let things grow wherever they want to grow" camp?

Yes, we all agree that MAN is the cause of all the issues to begin with - man disturbed the land, man imported the plants and the pests and the diseases. All that is true.

But what now? Do we keep planting and distributing recognized invasives? Because some people still do. Do we spend resources (volunteer time, professional money?) to reduce the spread, at least in natural ares like parks and conserved areas?

I absolutely think there need to be strict laws in every state in the US regarding the distribution of invasive or potentially invasive species. WA, OR, HI, MA, and a few others are on the cutting edge. I've also heard that some communities now require property owners to remove invasive species from their land.

PS. To set the record straight I posted above that Gardens Alive is selling Burning Bush seedlings. Just checked the catalog and it is actually Norway maple seedlings. How any self-respecting nursery can sell this weedy and fugly tree, I don't know. Perhaps it is not invasive in the arid climates out west?

The biggest defense I see by people choosing to plant them is "my property, my choice." And, that is the problem-- we think we can actually "own" land, trees and other natural things. :-)

That's a long way to fly without pooping! So you're saying they can eat something in Turkey and then fly all that way without pooping out what they ate until they get here?

EuroAsian starlings are artificially introduced to North America. I would like to hear your opinions on this.

I think it's terrible. They should not be here.

What are the reasons that you feel EuroAsian stralings should not be here?

From The Cornell Lab on Ornithology:

"In 1890-1892, about 100 starlings were released in New York City's Central Park as part of an effort by the acclimatization society to introduce all birds mentioned in Shakespeare's writings to North America.

Starlings are now one of the most numerous birds in North America. There are more than 200 million starlings across most of the continent.

These birds compete with many native species especially birds that nest in cavities (holes in trees, on the side of a cliff, or in birdhouses).

Starlings aggressively "throw out" nesting pairs of other species from their nests. They often destroy eggs and kill nestlings of many native species, including woodpeckers, Tree Swallows, Eastern Bluebirds, and Purple Martins. The populations of many of these and other native cavity-nesting species have declined."

Doesn't sound like a bird that "plays well with others".

Why do YOU support them?

For example, what if, uh........Picea pungens-Colorado spruce, was to somehow creep across the plains, perhaps get up into the Dakotas, and then eventually find itself in the W. Great Lakes region. According to those who would freeze "native plant communities" in time, this would be wrong somehow.

I'm not suggesting such is, or could happen. Only fishing for an example of what I see as a too-rigid stance by some in the industry, as though they themselves know the sum total of all that a given ecosystem should consist of.

Probably a lesser problem than the attack of known bad invasive plants, but still, an area of concern. It is not too distantly related to the other thing I complained about earlier-the tendency for the "prairie people" to not realize that their beloved grasslands were only a waystop for many sites along the continuum back to forest. Not saying such was the case in say, Nebraska, but central Wisconsin? Of course!

+oM

If you find dawn redwoods to be invasive in Appalachian forests, I'd really like to hear about that. (-:

Now, a recent research show that invasive Pythons are linked to the short-term decline of deer and rats in Florida Everglades. The population of racoons and opossums had dropped by about 99%. The impact to the environment is yet to be studied.

One thing against conservatism is that the world is a constantly changing and evolving one.

Is there anyone who believe evolution is a false prophet here?

Has anyone approached local nusery owners as to why they continue to promote and sell invasives?

Has anyone here knowingly planted an invasive? If so, which plant and what state are you in?

Raccoons completely suck. In Houston, in the middle of urban.... they completely took over my mother's attic. From what I've heard, it was completely mess. Next door neighbor feeds them! Crazy...

To me, it's sort of like the climate change issue - yes, climate has changed naturally in the past, but that doesn't mean it's a good idea for us to cause it to change now (NOT that I want to start a debate about whether that's occurring - we only have a few posts before this thread reaches its limit). Yes, extinction, migration, and landscape changes are inevitable parts of nature, but that doesn't mean it's wise for us to rush the process along by introducing and spreading invasive species (or uncontrolled fragmentation and development, etc.).

That said, there is the flip side of the coin that wisconsintom is talking about - those that seem to believe that a natural community can or should be preserved or restored as a sort of fixed museum of pre-Columbian flora. That is clearly not realistic and may not be desireable in all cases, even aside from the issue of invasives.

Birds can carry seed in ways other than their crops (stuck on feet tangled in feathers) and yes they do go trans oceanic on occasion (there are forums devoted to accidental or vagrant birds... Birders love that stuff) but over thousands of years I don't think species introduction from this amounts to much. Look at Hawaii. Millions of years and only a few species have crossed the water.

I like how saccharum explained it.... If I get it right he's saying we should avoid encouraging invasives but for the ones that are there the best you can hope for is tempering it's spread and hope that our natives can hold on till a new balance works out.

And for the record I like raccoons more that 15 foot long snakes.

Now as for a "plant natives only" approach..... I've got tons of problems with that too. But I think OP doesn't want the thread to go there.

I am not sure why people think that those of us that advocate for the reduction/removal of invasives and/or advocate for the increased use of native plants in the garden are people that insist on planting natives only.

This point comes up all the time - as if to indicate that we are zealots and not worthy of reasonable discussion.

I like non-native plants as long as they are not invasive. I have in my garden: daylilies, gardenias, non-native viburnums, tea olive, colorful annuals, a bit of lawn. These are all great plants. But they do represent a very small part of my plantings, perhaps only 2% total. I see no reason not to enjoy them when they behave themselves.

And no I'm not trying to return natural areas to a pre-Columbian museum. But I would like to think that "natural" areas like parks could be MOSTLY native plants, especially in the natural areas themselves (not talking about what is planted around the office and the bathrooms, I mean the trails and the waterfalls). In two weeks I'll be volunteering at a State Park removing japanese honeysuckle from around the waterfalls.

It is obvious that we will never clear out all invasives; it is physically impossible at this point. But we don't need to be planting them on purpose and we can do what we can to remove the ones we find ... especially when they pop up in our own yard!

I feel if you observe Japanese honeysuckles seem to be too dominant, it is good to volunteer to remove them. You work clears out the land for at least a few years. Just make sure you do not mistakenly take out misidentified native plants.

But most people really do not bother with anything of such. It is very expensive to remove them. I removed two clusters of Japanese honeysuckles from my yard before. It set me back $2000.

On the other hand, some target the nurseries. As one of the pro-nurseries pointed out, if you can dig one from across the street, why he couldn't have one in his yard.

Sometimes I feel discouraged, and wonder whether it's worth it, especially when looking at some of the masses of Oriental bittersweet thickets smothering trees and edge habitats throughout the neighborhood (I cut those sometimes too). It doesn't help that small flocks of Starlings will occasionally pass thru the yard, perch in one of the canopy trees, and poop out a bunch of bittersweet berries.

This statement sounds very scientifically un-neutral (to use verbiage from another recent thread). Depends on the chemical, the way it's applied, the plant in question, etc. In many cases, the payoff of using chemicals would be hard to reasonably argue against. The potential use of chemicals, needed to control many invasives, might make a wonderful argument against planting invasives in the first place. The more that invasives are planted, the more herbicides may be required.

No, actually they don't. There may be some instances where this has occurred, but, when used correctly, most herbicides would not make it into drinking water.

"Do you know any clinical study of the impact of herbicide?"

Many, many, many, many.....

And most modern herbicides are quite safe, when used correctly.

I will add a point that might go along with your thinking though...The mega-massive use of some herbicides in today's agriculture (much of it used against exotic invasives) may be worthy of concern. The old phrase "too much of anything is bad", comes to mind. For instance, even though glyphosate is tremendously safe on a small scale, what is hundreds of millions of pounds per year doing to us?

I'll let others step in to debate chemicals in the environment.... I'm going to pass on the bait that was thrown out there.

Even this entire thread, which from the title some might highly suspect of being "bait", is not meant in any way as bait. I honestly want to understand other's perceptions of the subject and would enjoy being able to fine-tune my own.

Running bamboo can be quite aggressive (irritating to some gardeners), but that doesn't mean they do any harm to the environment. Always consider the neighbors, etc. A thick grove of large bamboo is an awesome thing in the right place.

My son and I recently visited the Big Island of Hawaii - amazing place! Talk about an interesting study in endemic, indigenous, introduced, and invasive species. Anyway, we visited the Volcanoes National Park, and had a fabulous guided tour through a Volcano rainforest. The ranger educated the tour about the worst invasive plant in the park - Kahili ginger (Hedychium gardnerianum). Not only do they have to use herbicides in this pristine and beautiful place, they have to cut and hit these plants repeatedly to eventually kill them.

Mechanical removal would not be an effective way to control cogongrass in a pine stand (to re-use that example), unless you were willing to kill the pines as well; the majority of the biomass of cogongrass is in the rhizomes underground, and it takes deep, repeated plowing to control it mechanically.

I think that herbicides (and other pesticides) should be used with due care and not over-used, but as with human medicine, I don't think they should all be discarded just because some have caused harm.

Mackel in DFW

Snax, thanks for that startling insight! Woke me back up. It was very curious to me that a few of the worst invasive plants on the North American continent, including my back yard, are also a problem on the Hawaiian islands - Buddleja davidii, Lonicera japonica, Elaeagnus umbellata, Ligustrum, Tamarix, Pampas grass, etc. Amazing that some of these species are so adaptable.

Nope, I'm with the CIA, currently working to update top secret personal records on those that knowingly plant invasives.

Likewise, I've planted hundreds of Larix marschlinsii-hybrid larch. Meanwhile, in the woods nearby are tamarack trees-American larch, AKA Eastern larch. So, given that larch species quite freely hybridize when grown in close proximity, it seems possible that I could be setting the stage for such hybridization to take place. Call me a hypocrite, but I don't fear the consequences were such to happen. They would be larch trees, but not exactly the same as the native ones nearby. I like hybrids, whether created by nature where two similar species' ranges overlap, or done intentionally by man. the results are very often, strong, vigorous plants with nice attributes. I wouldn't mind it at all if this were to occur on my land.

+oM

I fear that an inevitable and relentless pressure on the Earth' resources due to a growing human population will result in an unceasing extraction the earth's resources until perhaps the last usable drop. Coincidentally, humans have presented relatively little understanding of the natural world, very little restraint over our greed and appetites, nor forethought of the results of our actions. Even with something as obvious as cutting down all the trees on Easter Island! Which apparently, invasive rats had something to do with as well, because they ate the seeds of the trees.

I don't believe we have any idea what evolution will bring in the context of the pervasive chaos we have created with natural systems. I still think it's worth the effort to try and maintain some high-quality and intact native habitats. Someday in the future, it might be nice for people to have places where they can visit and experience what the earth used to be like.

Chinese is a unique language which requires both brain lobes to master. So, from my perspective, your logic is strictly linear. I guess you probably would not understand what I see completely.

Speaking from a biologist's perspective, I can say with confidence that everything is interrelated and woven into a context, where a cascade of unknown events is caused by changes in each and any part of the whole, as it appears that only the cerebral connections in our esteemed Dr. S may escape this fundametal law.

Oh, plus, based on the way GW divides topics, "invasive species" should have separate forums.

Upon reviewing all of GW's forums, I can't find even a single example of where GW has provided a forum for this type of topic. On top of that, an Invasives Forum would probably tend to invite more controversy than anything else. Probably the best place to discuss invasives in general on here is the Botany Forum, which is often a little more science-related than most other forums. I chose to bring it up here because it's frequently a topic of discussion in this forum and because I specifically wanted to hear the opinions of the Tree Forum peeps.

Natives, Woodlands

Wildflowers & Native Plants

Professional Topics

Education

Botany

Tips & Techniques

Pests & Diseases

Volunteer Gardeners

That way, all involved in the discussion get the whole picture. Separating it off to a single forum would not get nearly as much participation and would probably be a case of "preaching to the choir".

You might even make an opposing case that could help others in the way that they think about the subject. This could trigger a spirited response from those who can articulate why they might disagree, there's nothing wrong with passion and philosophy going hand in hand.

However, there are rules of engagemnt and discussion, first articulated by the great philosophers of history's past, that one should practice in order to avoid the logical errors of the shaman, that the philosophers eventually replaced.

Off to the garden and thankyou for your consideration and interest, and any contributions that you might have.

+oM

+oM

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.

+oM