Purple Loosestrife Cultivars

I just read another article on purple loosestrife as an invasive seeder.
I am certainly sensitive to concerns re wild purple loosestrife (it clearly speeds up floral succession), but feel the case is greatly exaggerated, if it is extended to cultivars. I have grown cultivars bought as 'Morden Pink', 'Rosy Gem' and 'Terra Nova'. I've grown the 'Morden Pink' and 'Rosy Gem' for nine or ten years in three different gardens which I still maintain. I've never seen these cultivars seed once. Two of these gardens have sprinkler systems (not the best for a perennial garden) and I am a careful waterer in my own garden. Presumably, my purple loosestrife cultivars get a fair bit of moisture. I am probably quite a meticulous (perfectionist?) perennial gardener, never use toxic chemical, do hand and hoe weeding and like to police the surface of the ground (though this gets more and more difficult, in a perennnial garden, as the seasons advance). I would have thought that I had given my purple loosestrife cultivars ample chance to seed, if they could. They never have. I also know of a very large garden of a friend, where long established purple loosestrife cultivars have also never been a seeding problem.
I would never plant, even the cultivars, in cottage country (for us, the Lake-of-Bays, On). I have not even planted purple loosestrife cultivars in gardens with adjacent woodlots.
Purple loosestrife cultivars are beautiful plants. In my own garden, the three biggest bee drawing plants are culver's root, globe thistle and purple loosestrife cultivars. It is very relaxing working among the bees They do their thing and I do mine.
I have read of purple loosestrife cultivars seeding in the past. I don't know why I have never seen it. There are obviously many different possible explanations. Nevertheless, if I'm to stop growing purple loosestrife cultivars, I would like to see a stronger case made against them.

This message was edited Mar 11, 2009 10:46 PM

I found your post interesting because I have just faced the same issue. I am a member of the Chicago Botanic Garden and looked at their list of invasive plants Monday, which lists purple loosestrife but not its cultivars. They do not, however, have any of the cultivars in the garden.

I have had a Morden's Pink in my garden for over 20 years. It has never produced a seedling. I, too, have felt that the attack on the cultivars was a bit hysterical.

I contacted CBG and asked if I should remove my plant. They replied as follows:

"The Lythrum variety you have in your garden is a cultivar of the native species that we have on the Chicago Botanic Garden invasive list and thought to be sterile. From that perspective, it does not appear on the list. That said, following is a link to the Manitoba Purple Loosestrife Project. See Question #2 where research shows that ‘Morden’s Pink’ grown near natural areas may still cause problems."
http://www.purpleloosestrife.org/faq/index.html

There it states that cultivars planted near wild loosestrife do produce viable seed. It did not explain how near is too near but I know that purple loosestrife is a problem in areas within a few miles of my home. Therefor since my plant was pretty but had never done spectacularly well in my yard and was in an area not highly visible from most parts of the yard I decided to remove it. I felt kind of bad about it but now I have a spot for a new plant which is a plus.

I don't know if the situation is worse where you are but your decision to wait until more convincing information comes along seems reasonable to me. You may find that link interesting if you haven't already seen it.

The Chicago Botanic Garden is in the midst of a project to remove or phase out invasive plants and I'm sure it is pretty traumatic for them as they will be giving up some very beautiful plants including trees and shrubs. They will take 5-10 years to phase out larger species that form major structural features in the gardens. That has to be painful but then it will also be exciting to choose replacements and rework the areas affected by the removals.

Hi chris_h,
Thank you for your thoughtful reply.
Have done a bit more reading on purple loosestrife cultivars, but need to do more. At the present time, I still get the feeling of Big Brotherism in this matter.
I'm looking at a report of the study "Fertility of 'Morden Pink' Lythrum virgatum L. Transplanted Into Wild Stands of L. salicaria L. In Manitoba" (1993). In this study, 40 'Morden Pink' transplants were put into three experimental sites: two along rivers and one in a small wetland north of a river. At this point in time no responsible gardener is going to plant purple loosestrife cultivars anywhere near rivers and wetlands (obviously yourself included). We have a family cottage on the Lake-of-Bays and I would never think of taking purple loosestrife cultivars anywhere near there. Most people who know nothing about horticulture don't plant anything, including purple loosestrife.
I must say I resent being apparently told in the article (Manitoba Purple Loosestrife Project's Top 10 FAQ), to replace 'Morden Pink' with gayfeather (Liatris). Or is the article only directed at Manitobans? What species or cultivars of Liatris ever attains the five foot mentioned (at least where we live on the Oak Ridges Morraine)? Although I grow lots of Liatris spicata, how can it be equated with 'Morden Pink' in terms of showiness, bee attracting ability or longevity in a perennial border?
I would also feel a lot more comfortable to be informed of the research which substantiates the claim that "most loosestrife infestations originate from garden cultivars" (in Top 10 above). And I would then want to know which cultivars and what studies.
I don't care for facile pronouncements and assume they won't get ready acceptance from seasoned gardeners.
I commend and sympathize with you for doing what may be necessary in the area where you live.

This message was edited Apr 9, 2009 12:13 AM

I must say, I agree with you that Liatris is no substitute for Morden Pink. While my Morden never reached 5 feet - maybe 4 at most, it's flowers had such a beautiful delicacy and the color glowed in the sun. It's a shame that they are talking about eradicating even the cultivars. The attack on them doesn't seem to be quite that extreme here in Illinois yet but it may be heading in that direction. I hope and assume that these plants will continue to thrive in their native habitats wherever that may be.

The statement "most loosestrife infestations originate from garden cultivars" interested me too, as it would seem to justify the campaign against them and yet it doesn't make sense to me since it is still the species, not the cultivars that are overrunning native vegetation. Or maybe I'm wrong about that. I just don't really understand it.

Anyway, best of luck to you. I hope you get to keep your loosestrife cultivars for many years to come.

Chris

Hi Chris,
We're on the same page!
One senses, maybe incorrectly, that the statement that bothers us lacks an academic basis.
Hope our paths cross again.
Sunny


This message was edited Apr 9, 2009 4:10 PM

The science of cultivar reproduction is quite straightforward, as I understand it. Cultivars are clones, propagated by divisions or cuttings. Therefore, depending on the species, a plant that is a cultivar can be sterile in the sense that it cannot cross-pollinate another individual (clone) of the same cultivar. However, a plant that is a cultivar can cross-pollinate other individuals of the species that are not genetically identical clones, i.e., escaped wild populations or other cultivars of the same species. That's the reason why it's generally very unwise to plant cultivars of invasive species. They can easily cross-pollinate genetically non-identical individuals of the same species.

I'm not a scientist, but this is what I've read!

I'm sorry but this thread has my jaw on the floor. You REALLY need to have this plant??? There are indeed many alternatives. Why would you even risk the smallest chance of introducing an invasive species??!! I'm sorry but not every gardener is "responsible" as mentioned above. You can't say without question no one will plant this plant near wetlands. Wetlands are too precious to loose anymore. I am wholeheartedly in favor of banning this plant. There are plenty enough plants in this world that are cultivated. No one really NEEDS this invader.

Here is more info:

REPRODUCTION AND METHODS OF DISPERSALIts prolific seed production, up to 2.7 million per plant per year, enables purple loosestrife toestablish dense stands within a few years. Purple loosestrife spreads by seeds that may be distributed by water, by wind over ice in the winter, or by clinging to the feet of waterfowl. These seeds canremain viable 10-15 years and once germinated can reach sexual maturity in 8-10 weeks, thusflowering in their growing season. High seed viability (up to 99% in the first year) and prolific seed production can build up a seed bank of massive proportions. It can also spread vegetatively byformation of adventitious shoots and roots from clipped, trampled, or buried stems. Theserhizomes can grow as much as one foot per year.

EFFECTS OF INVASIONAn invasion of purple loosestrife leads to a loss of plant and wildlife diversity by affectingbiogeochemical and hydrological processes in wetlands. Seeds are usually present in large numbersand germinate in such high densities that growth of native seedlings is prevented by what quicklydevelops into a monoculture of purple loosestrife and dominating the wetland environment. Thebuild up of other debris around the roots enables loosestrife to invade deeper water and to formdense stands that shade out and push out floating vegetation by closing open water spaces. Theimpact of purple loosestrife is seen in the loss of native flora and fauna in affected wetlands,degradation of wetland pastures and wild hay meadows, clogging of irrigation systems, and the lossof natural habitat for recreational enjoyment

.NATIVE ALTERNATIVES FOR LANDSCAPE USEPurple loosestrife has long been used as a garden ornamental because of its attractive, long-lastingspikes of purple flowers. The claim is frequently made that horticultural cultivars do not produceviable seed and thus are not a threat to natural areas. However, it has been shown experimentallythat garden forms of purple loosestrife do cross-pollinate with stands of the rare native species,winged loosestrife (Lythrum alatum), resulting in viable seed production.Native alternatives to purple loosestrife for garden use include: Joe-pye-weed (Eupatorium fistulosum,E. maculatum), New England aster (Aster novae-angliae), purple-stemmed aster (Aster puniceus), NewYork ironweed (Vernonia noveboracensis), obedience-plant (Physostegia virginiana), bee-balm (Monardadidyma), hardhack (Spiraea tomentosa), swamp milkweed (Asclepias incarnata), blazing-star (Liatrisspicata), great blue lobelia (Lobelia siphilitica), and cardinal flower (Lobelia cardinalis).
--------------------------------------------------------------------------------

As clearly stated in this article, seeds are not the only method of dispersal. In addition if viable seed were produced, it can be dispersed very far away from your own plants via insects, birds, and other wildlife. I'm sorry, but there is just no need for such a destructive plant. I would highly recommend ironweed as an alternative. It blooms in late summer and fall, there are a multitude of species available, height is anywhere from 3 ft to 15 ft, and it attracts many butterflies and is a fabulous late summer/fall nectar source for bees. The seedhead can be used dried as well, and it is a great fresh cut flower. Very easy to grow, and NATIVE. It doesn't even reseed where I have it, and it is native. Doesn't spread by runners either.

eta:
here is another excellent article on purple loosestrife:
http://www.seagrant.umn.edu/ais/purpleloosestrife_info


This message was edited Apr 9, 2009 8:39 PM

I don't believe for one minute that "the science of cultivar reproduction" is quite straight forward. On-line academic articles clearly show that it is not.

Purple loosestrife is a hermaphrodite plant (male and female: it's main method of reproduction being by seed dispersal). I take it that the original 'sport' of a cultivar like 'Morden Pink' was an hermaphrodite that had developed self-incompatability (the plant couldn't fertilize itself). It was then determined that the self-incompatability is lost when the cultivar is crossed to related plants.

You can read, on-line, detailed analysis of seed production involving cultivar crosses with wild purple loosestrife. When it comes to the situation in gardens, however, one reads anecdotes like "some gardeners report".

For gardeners the issue is, is there any harm in using purple loosestrife cultivars if they are not used around environmentally sensitive area? In the apparent absence of scientific research involving gardens, gardeners are obliged to fall back on their own experience. I've had Lythrum virgatum (salicaria) 'Morden Pink' and L. salicaria? 'Rosy Gem' in the same well watered perennial beds for ten years and never see any seed production. I also have these around Lythrum anceps and again I've never seen any seed production. I know I'm not the only gardener with exactly the same experience.

I really can't help wondering whether an agenda is making up for gaps in the scientific knowledge?

This message was edited Apr 10, 2009 5:27 PM

If there's an "agenda", it's making money from selling plants no matter the consequences, not protecting wetlands.

I thought the lesson about sterile cultivars was learned the hard way with Callery pears. Pollen...not necessarily seeds..

I don't understand why the research has to apply to gardens specifically, instead of how plants reproduce. Do plants somehow behave differently in gardens?


It always amazes me how no one ever sees their own plants as being invasive - it's never in their own yard, blah, blah, blah.

I'm sorry about your jaw trillium612, but we obviously disagree.

The issue is that the cultivars in the garden do behave differently.
I agree with you that there are lots of differences of opinions about the invasiveness of particular plants.

I am as concerned as trillium about gardeners being more concerned with the keeping flowers with the potential of damaging the environment for their pleasure. As dedicated gardeners I believe our most important focus is keeping the environment healthy and having the least destructive impact personally. My world is suffering from the invasion of purple loosestrife. It has become such a problem here that last year the state and feds collaborated on the importation of beetles that supposedly only feed on purple loosestrife. I am a bit concerned that if these beetles are able to eradicate the problem, what other problems will the introduction of these beetles create.
I have seen this wild purple loosestrife overrun a salt water marsh and while it looks pretty, it eliminated the native vegetation and has created hardship for the animals that depended on that native vegetation for sustenance.
I would ask Sunny to rethink their position while it is still viable.
diene

Respect your opinion diene.
Do volunteer gardening and would be quite happy to help eradicate any purple loosestrife in community wetlands, if was any.
Sunny

Interesting article:
http://www.artdrysdale.com/june2001.html

(Canada has banned some uses of lead shot)


This message was edited Apr 13, 2009 12:46 PM

I don't need to read an old study to know that streamsides around here aren't supposed to be purple.

Have you read any of this? It is not simply "an old study". It's the points made by the academics, referred to, which need to be answered by other academics. Science isn't based on personal observation and I feel very uncomfortable being forced to rely on personal observation in the apparent absence of scientific research.

I read all of it. I was referring to the 1998 study that,"found little scientific evidence consistent with the hypothesis that purple loosestrife has deleterious effects." It's replacing native plants around here, that is deleterious enough for me


And this, from 1995, “that studies of competition between loosestrife and other plants are few, but of those conducted in the field, some have shown that loosestrife seedlings cannot compete with native species and that stands of loosestrife were frequently invaded by native species....".

I guess we know how that turned out. It looks to me like the loosestrife has survived the invasions "by native species", whatever that means.

In your first post you make it clear that you would "never plant, even the cultivars, in cottage country (for us, the Lake-of-Bays, On). I have not even planted purple loosestrife cultivars in gardens with adjacent woodlots."

Why not? I don't get it.

The "an old study" confused me, because as you indicate above more than one study is referred to. The Manitoba study, which seems currently to a be heavy armament in the anti-garden-cultivar camp, was published in 1993 (is even older).

I think the article is interesting for the unease it demonstrates among long-time gardeners-horticulturalists about what seems to some to be a purple loosestrife hysteria. I don't think the decrease or not of biodiveristy in wetlands is relevant to the discussion of whether purple loosestrife cultivars should be used/allowed in any gardens.

The issue as I indicated previously is, do the cultivars like 'Morden Pink' contribute to any real or possible wetland problems? Hence, should they be grown in gardens? It seems clear that when they are planted close to wetlands they do produce seed. Therefore, they should not be planted close to wetlands (and lakes e.g. the-Lake-of-Bays)

It seems that cultivars like 'Morden Pink' , in gardens, do not produce seed in gardens. Gardeners who like the cultivars need to see evidence of research to the contrary, before they stop using the cultivars.

The best argument that I have seen to date, for not using (or banning)
purple loosestrife cultivars in (from) all gardens, is the argument that people can't be trusted to keep them away from wetlands (or lakes). I don't like this approach, however well intended it is.

That is some very misguided information you sourced Sunny. Do you want to really know why anglers and hunters are working to get rid of purple loosestrife?

It chokes out native plants that are the host plants for native insects which are what native trout and other fish feed on. It cause wetlands to fill in faster, chokes out springs, and makes streams warm up. Native trout, as well as many unique minnow species require cold water. Cattails can have the same effect really. It has nothing to do with wanting there to be nothing on the banks to make casting easier. That is an extremely naiive and biased POV. Banks need to be stabilized, but it should be with native plants, than are a part of the whole ecosystem, supporting native wildlife.

Dense stands of loosestrife are too tall to make good nesting habitat for water birds. They also harbor predators. That can increase predation and hurt alot of different species. The waterfowl in Canada migrates through the US, and in some cases as far south as Brazil. So, just this one impact can affect what happens thousands of miles away. It is no secret that seeds and plant bits can be carried thousands of miles by migrating birds. Canada is the waterfowl factory of the world. When your wetlands are diminished, it affects this entire hemisphere!!!! This is why DU and Delta waterfowl work against this plant, and many other invaders. It has nothing to do with hunting. Myself, and people like me all over this continent volunteer and donate to these programs and do it because we love waterfowl, not because we have some insidious intent to have more animals to kill. I spend by far more time watching, and photographing waterfowl than I do hunting them.

As far as the lead ban. lead shot was banned many years ago for hunting migratory birds, in the USA anyway. That argument simply has no merit. Lead shot is banned on all federal property in the US. Some states have even more stringent laws, including banning lead shot in sporting clay and trap events. Lead sinkers and jigs for fishing are also being phased out in the US, as well as leadcore line and leaders.

So I'm sorry, but if you are making the argument that people who want to ban loosestrife are doing so for some nefarious reason of personal gain, while they do more damage using lead, then that argument has no basis in fact, and you are the one who needs to find some more scientific sources, instead of linking to an article that was obviously written from an animal rights POV and is clearly anti-hunting and fishing. There is no such thing as a safe place to plant an invasive species.

The whole thing is that purple loosestrife CULTIVARS, IN GARDENS, are NOT invasive. It would be very helpful, if you would answer that.

Can someone answer this question for me? This is a serious request, not a snide comment.

Suppose there exists a large infestation of purple loosestrife in a wetland area. A few miles away there is one Morden Pink cultivar in my garden. Even if that one plant is capable of cross pollinating with the wild plants several miles away how does that make matters any worse? Aren't the wild plants already getting pollinated without the cultivar's help? And if the garden cultivar is cross pollinated why does it never produce a seedling in my garden?

I guess you can see I don't understand the science.

I have removed that Morden Pink from my garden but emotionally I still feel unconvinced that it was really necessary. It's just hard to ignore the evidence we see with our own eyes. Many of us have had these cultivars in our gardens for decades without a single seedling appearing. So when studies say, yes they can produce viable seed, it just doesn't seem real to me. Still, I know my "emotional" reaction has no scientific merit.

Would it be fair to say that the eradication of all cultivars is sought because although it may not be necessary, it's better to be "safe than sorry"?

I'm just about to remove the Miscanthus sinensis from my garden because it is on the invasive plant list from the Chicago Botanic Garden. I'm wondering if more plants in my garden may be labeled "invasive" in years to come. I will always want to do the right thing but I would like to understand it better.

Thanks

I have purple loose strife in my garden, for 4 years now I think, and have never had any seedlings. I have no idea what variety it is, a nice old lady gave it to me. It grows fast, blooms ALL summer and is a gorgeous color. I would never part with it!
I have one, my mom has one or maybe two.

FrillyLily, It's been illegal to plant purple loosestrife in Missouri since 1989. You say you would "never part with it", yet it's likely that seeds from your plant are spreading. Each plant has hundreds of thousands of seeds - can you account for where they went? Probably not.

SunnyBorders, you haven't asked a question but you want an answer. ? Well, nobody cares if it's invasive "IN GARDENS" or not. But when garden plants take over natural areas, it's a problem. Taxpayers bear the burden of cleaning up your mess.

Chris_h, the seedlings from gardener's plants grow in wetlands, where there are no lawnmowers or herbicides and lots of water. A cultivar's seedlings wouldn't look like the parent plant, which is why the wetlands and streamsides have the regular species growing, not 'Morden's Pink' or whatever. The cultivars were banned when scientists learned they were not sterile. There's lots of info on the web if you're interested.

Great post claypa. In addition, when crosspollination occurs, you may end up with a new hybrid that will be more resistant to herbicides, diseases, and insects, therefore more difficult to eradicate, and faster to spread. Without genetic testing, there probably isn't much way visually to say, "oh that one is crossed with a Morden's Pink".

I refuse to believe my plant is making any viable seeds at all. It is in my garden, in ideal soil and well cared for. Therefore if it were producing viable seed, it would be sprouting all over my gardens, just as my hibiscus and other seeds do.

http://www.mdc.mo.gov/conmag/1998/08/50.htm

Here is a link to an article concerning the sale of seeds, plants, and how the Missouri Dept of Conservation controls Purple Loosestrife in Wetland areas and other areas around the state.
They do not pursue private gardens where the plant is maintained. Also, they are not able to treat plants on private land without the landowners permission.
Ornamental types that do not produce viable seed, are still legal to plant in MO according to the article on their website.

"Ideal soil" for loosestrife is a wetland or a stream bank.

I wonder where all the purple loosestrife and other invasive plants in the wild come from, because nobody ever sees them in their own yard. It's an amazing phenomenon!

It invades wet lands, not yards.
I guess you didn't read the link I posted above.

""Conservation Department biologists will continue to track populations of purple loosestrife in Missouri and attempt eradication wherever possible. You can help by reporting any wild populations. We are not interested in locations of ornamental plantings where plants are not spreading from the planting site. For a descriptive color poster, write Purple Loosestrife Poster, Natural History Section, Missouri Department of Conservation, P.O. Box 180, Jefferson City, MO 65102-0180."""


"""Two species of plants, numerous hybrids and selections of these are called purple loosestrife. One of the species, Lythrum salicaria, was declared a noxious weed by the Missouri Legislature in 1989. This prohibits the sale of that species or any of its hybrids in Missouri. It is also unlawful to distribute or plant its seeds or any part of the plant in the state.

The other species, Lythrum virgatum, and its hybrids do not usually produce viable seeds. Therefore they do not spread and are still legal to sell as potted plants in Missouri. Some states have prohibited the sale of all purple loosestrife because of the difficulty in determining which plants are aggressive spreaders and because cross-pollination of non-spreading plants can produce ones that spread. The sale of any purple loosestrife seeds is illegal in Missouri."""

I did not buy/plant seeds, I planted a potted plant.
I assume now that it is a hybrid because it has never had any seeds sprout in my garden. It is in ideal soil. It is watered regularly, sprayed for pests, dead material is trimmed out, mulched in the winter and fertilized. I don't know how more ideal it could get. It's not trying to grow on some dried out clay bank somewhere with no attention. It flowers all summer and it were to have viable seed, it would have did it before now. So it seems to me that according to the MDC website, I have a perfectly legal plant.

You said you had purple loosestrife in your garden, not me.

Think everybody has good intent on this thread, but I don't think relevant questions are being answered: the cultivars don't produce seeds in gardens. They only produce seeds when they are planted near (in?) wetlands.
The issue is then: how are the cultivars, in gardens, invading wetlands? It can't be by seed dispersal because they don't produce seed. If the garden cultivars produce pollen and bees carry it to wetlands, what would the bees be pollinating if there was no wild purple loosestrife present? If there was already purple loosestrife in the wetland, why wouldn't the bees be simply pollinating wild-to-wild purple loosestrife plants? If this is about garden cultivars losing their self-incompatability, why do they only do it when they are physically taken and planted in/around wetland areas?
It doesn't seem that questions such as these are being answered by those who write about current scientific knowledge for gardeners. I'm forced, in fact, to wonder how complete the relevant scientific research really is.
The relevancy I'm talking about is whether gardeners should grow purple loosestrife cultivars, or not.

I live in Illinois. Lythrum salicaria is banned in Illinois. Morden Pink ( Lythrum virgatum) is NOT banned nor are any other cultivars. So it is perfectly legal for me to grow Morden Pink.

I turned to the Chicago Botanic Garden for advice and since they do not have Morden Pink in their collection, I decided to be cautious and remove mine. But I think it would also be an ethical choice to keep your cultivar, if it is not banned where you live, as long as you watch carefully for any research that may yield new information.

Has any genetic testing ever been done to confirm that L. virgatum (Morden Pink) or L. virgatum / L. salicaria crosses are in fact infesting wetlands? I have not seen any articles that site such tests. Surely this would be critical information.

I don't know, but apparently research exists that proves no Lythrum is sterile, as far as the PA legislature was concerned. They probably couldn't afford to chance it, after what happened with "sterile" callery pears that are now everywhere. You could ask the U. Illinois extension, which says they are "supposedly" sterile; they cite research but not specifically:

http://web.extension.uiuc.edu/champaign/homeowners/990515.html

"Some cultivars are listed as legal in Illinois. However a wealth of research is showing these cultivars are not as harmless as once thought even though they are derived from a different Lythrum (Lythrum virgatum). Supposedly the seeds are sterile and will not reseed. Research has shown the pollen is viable and will pollinate the weedy species."

http://faq.gardenweb.com/faq/lists/pagard/2003075032032141.html

Here's the original massive pdf explaining the rationale for the Pennsylvania law, starting on page 31

http://www.pabulletin.com/secure/data/vol30/30-47/30-47.pdf

I really liked diene's statement, "As dedicated gardeners I believe our most important focus is keeping the environment healthy and having the least destructive impact personally."

I think the general public is running out of patience for gardeners' "need" for plants that might or have already damaged ecosystems on public land. And maybe they won't wait for proof that the genie is already out of the bottle before they act.

"The bias toward landscaping with alien ornamentals has been so complete that the first trophic level in suburban/urban ecosystems throughout the U.S. is now dominated by plant species that evolved elsewhere."

http://copland.udel.edu/~dtallamy/host/index.html

I completely understand the urge of gardeners to want plants that are unusual and new. I am a sucker for the "new" choices at the nurseries every spring. But lately I've been thinking that the quest for ever new and exotic plants for our gardens is maybe an outdated practice. This year I am going to look for native plants that are new to me. I am sure there are many. How about all the new varieties of Echinacea? Those should be safe, shouldn't they?

By the way, are there any state or federal regulations about importing plants for sale in the United States? I have often wondered when I see "new" selections at nurseries or in catalogs if there is any effort made to determine whether the "new" plant might pose a threat to native plants. Would there be any way to do trials to test for that before allowing importation or are there just too many variables to make that realistic?

Anyway, I think I have now removed everything from my garden on the Chicago Botanic Garden's list of invasives. I only had three things that had to go so it wasn't too hard.

"they cite research but not specifically".
Personally, I'll be persuaded by specific research cited in appropriate sources.
Haven't seen that yet.

There's an e-mail adress in that article, you could ask them what "wealth of research" they're referring to.

Your interest in this thread is selective. Your comment on April 25 suggests you have no interest in the horticultural side of this issue (nobody cares ---). I and others do.
If I had been you, I would have wanted to know the evidence for a "wealth of research" before I used this quote to make a point.
I will E-mail the Unit Editor and ask for the research she refers to. I'm probably a good person to do it because of my academic background (which includes 'scientific' research).
I will report back to this thread as things go.
Sunny

If you had been me, you would have accepted that Lythrum cultivars pollinate other Lythrum plants when it was proven, and not wonder whether a garden was used in the study. And you would be weary of seeing the creek turn purple again.


http://www.sgnis.org/publicat/papers/jamsh851.pdf

My library can't access jstor articles, maybe yours can:

http://www.jstor.org/pss/2446161

To my knowledge, the word 'prove' is not used in Science, perhaps we could drop it.
Good references to show the type of research.
First: had read the abstract of Anderson & Ascher (1993), now have whole article. Got second: abstract for Strefeler et. al. (1996).

Split hairs all you like, but there was enough evidence for a number of legislatures to make laws about it.