Achanthus (bears breeches). I did it to myself. Loved the first one and bought two additional varieties. It took years to become overwhelmed by them but now there is a containment battle. Nothing kills them and they keep spreading. Hand digging every new baby bearly keeps them contained. I am zone 5/6.

Lynn, I almost purchased one of those! I'm so glad you mentioned this. I saw one a few years ago in someone's yard and loved it, but didn't purchase it. Around 5 or 6 years ago, it seemed to be the one plant that all of the major garden magazines were raving about. Who knew?

I gave all my babies this year to a garden club sale and they went like hot cakes. You just have to stay vigilant. The older I get the less vigilant I feel and hence they have gotten away from me. They are magnificent in full bloom in mass. I wish I had a picture to share. Maybe later, the flower heads are just forming now. I read the Romans planted them everywhere in their conquests because of their mednical properties and they are the leaves depicted on the columns. If you don't have energy, you should not plant them. But, the bloom is 2 feet tall and amazing. See I am sucking back in.....no.........it is the invasion of the body snachers. These plants never stop reproducing.

My neighbor around the corner has Acanthus in a raised shade bed that I love to see in bloom. I don't have the proper conditions but I think it is beautiful and would be tempted to try it if I did. I do have lily of the valley along a walk way and love it when it blooms, over roots of an Oak tree. Not much else can survive there (except mondo grass--another thug, and sweet williams if I water them) unless I build up the soil.

It must be that some Japanese anemone cultivars show a dramatically different growth habit in different growing conditions because, speaking only from my experience and those of my neighbors, we found that only 'Robustissima' behaves as a thuggish plant (pink, grape-leaved, and I believe it generally spreads by seeds which is not how others spread). I guess, besides specific cultivars, it all depends on the light and soil conditions and, of course, micro climate. And perhaps on our personal tolerance for the spreading rate... what might be 'aggressive' for some, would be considered 'slower' and manageable for others. I for one think that the gorgeous and elegant blooms that this plant gives us each fall more than compensate for any extra work in dividing them once in awhile. (I was also glad to see that many of its cultivars are endorsed by horticultural societies - a few got the Award of Gold Merit from RHS and last year 'Honorine Jobert' was named the plant of the year by the Perennial Plant Association.)

In my garden both robustissima & Honorine Jobert spread by roots (given the amount of each that I dig up, I'm quite certain). Both are great foliage plants and show stoppers in bloom but they need lots of space in Virginia. OTOH, my acanthus has been in stasis for three years. Maybe this year it will begin to spread. I gave it plenty of space thinking it would form a large clump so columbines have filled in around it. Columbines are very helpful like that.

"In my garden both robustissima & Honorine Jobert spread by root"

Indeed. Sorry for the ambiguity in my reference to 'Robustissima' -- came form a quick parenthetical note. I should have said "also" instead of "generally".

For invasives, I have to mention 'chameleon plant' (Houttuynia cordata). It somehow showed up uninvited in my raised bed and for two years I've been struggling to get rid of it with no success. I heard that it's been sold at some nurseries. All I can say is to stay away from it. No idea how it got into my garden but it's proven indestructible so far.

Forgot to mention that there's several on-line comments on the invasive nature of 'Robustissima'.

For example: Fine Gardening: "Noteworthy Characteristics: Can be weedy or invasive".

http://www.finegardening.com/grape-leaf-anemone-anemone-tomentosa-robustissima

I too am going crazy trying to get rid of helianthus. Japanese anemones have never been a problem...til now! This year fairy bells...the real name escapes me, have gone crazy. They even covered up the wild ginger, which actually hid a hosta. But recently the absolutely worst offender has been tradescantia. It is showing up all over the place, in areas I never planted it. It has totally overrun one small garden. Lily of the valley has done the same...has popped out 100 feet from the original place, and is covering up a bunch of astilbes. I'm in the Cape Cod area.

Interesting, Daylilyrose, how different problem plants seem to cause the problems in different years. As said, this is the first spring in which the some of the lamium has run (quite quickly) into other perennials.

Obviously, when the offenders were originally planted is one factor, but there also seems to be others.

As per your observations, this is the first year in which I've seen evidence of a tradescantia I planted (and have been watching) as a real seeding problem.

Years ago, when I was a novice gardener and frequently ordered from Wayside Gardens, I felt terribly cheated when I found just a small piece of root representing my order of Anemone Honorine Joubert. Had I been an experienced gardener at the time I would immediately have recognized the thuggish potential when all that was required to start a plant was a small piece of root! It took many years of determined effort to eliminate all traces of that Anemone! In the end I had to resort to double strength Roundup. And even then multiple applications were required.

Right now I am dealing with an extremely difficult garden thug. It's a form of Tricyrtis, though I can't seem to identify the species. It showed up in my garden for the first time about four years ago as an unfamiliar weed and after about 45 years of gardening on my present property, I'm pretty familiar with "my" weeds, so I noticed it right away. It didn't take me long to discover I couldn't pull it out. It has a long straight stem that dives down some four inches before the roots begin and then they branch out widely and laterally with thick fleshy "tentacles" that remind me of an octopus. It didn't take long to realize that leaving any root fragments behind would result in another plant or more. It takes repeated applications of triple strength Roundup applied repeatedly to kill the top growth and I'm still not sure it kills the roots. in spite of all my efforts, and I can tell you I've been homing in and killing these plants with considerable zeal and a large dose of hatred, I have an epidemic of new plants this year. I am beyond dismayed....

Here's a photo of a young one I dug up that was just pokng out its long stem. You can see what I mean about it's thuggish octopus like roots, though this particular plant was unusual in that the roots were close to the surface, Usually they are about 4" deep.

This is what it looks like as it's getting ready to bloom. The flowers are very tiny and totally unremarkable. Since Tricyrtis is not native to this continent it must be an invasive, though I have no idea why anyone would want to grow it.

Buddleja davidii

since we are getting our hates on, I am not going to miss an opportunity to do this unwanted interloper down. Pretty much every single pot in my garden has had buddleja seedlings in them...and I am vigilant. It is a horrible urban blight with nothing to recommend it.

We have Old Man Winter here, Camp, and he periodically eliminates Buddleja davidii.

Echolane, may be ignorance on my part but I don't recognize your excellent pictures/ words as Tricyrtis. Certainly not T. hirta which is not rhizomatous. Never used T. formosana, which can form dense clumps but which is not invasive (a reference I trust below).

You refer again to definitions of invasive. I would be happy to debate the issue. I just have no time for the sanctimonious bully boy/bully girl approach. I think that there are sound reasons to retain (and especially use) any of the several definitions/usages of the word

http://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?kempercode=a780

Now that we have gone to weeds.... while it has been building over the last few years, this year for some reason, I am completely overrun with Oxalis stricta (yellow wood sorrel). This stuff is the worst! I thought bitter crest was going to be my nemesis till death, but this clover wins hands down for 2017. It appears to be both an annual and a perennial. My internet searches say the littlest bit of root will regrow. I am overwhelmed by it. Why does it seem that a new weed shows up each year to torment? Bittersweet showed up this as well. Am I lucky or what?

Oxalis is a constant here. Any bare spot will soon show those tiny yellow blooms. Mulch and regular hoeing is the only thing keeping it from taking over. A few years ago a dark maroon oxalis showed up. The foliage was a bit larger and it was cute, for about a minute.

Yes, for a minute.

I find it rather revealing when one resorts to name calling to defend a position that really has no substance :-)

Regardless of any personal feelings about the terminology, there ARE accepted definitions of words. And I wasn't the one who assigned them!! Just Google 'invasive species definition' or 'invasive plants definition' and see what turns up. Moreover, to broaden the use of the term to include any plant one feels has an overly aggressive habit diminishes the impact true invasive plants have on the environment and unnecessarily clouds or diffuses a very serious issue.

As a degreed horticulturist, I attempt to use botanical/horticultural terms in the manner in which they are intended. And hopefully, to educate others as well as that is one of the underlying intents of GW from its very inception. If that is considered "sanctimonious" to a few, so be it - I've been called worse :-) Apparently there are a significant number of other members that also adhere to the accepted definition, as witnessed by discussions of the same topic on other forums and by the confirmation I have received on my previous comments to this thread.

'Old Man Winter' only goes so far in a country with as diverse a geography and climate as North America. As with any invasive species, location plays a very big role. Buddleia davidii is considered invasive pretty much anywhere along the west coast, has naturalized into wild areas in 20 states and is on the invasive species watch list for a number of mid Atlantic states as well and in 2007, the US Fish and Wildlife Service included it in a listing pf plants that should no longer be used in landscaping. Obviously "Old Man Winter" is not a sufficient deterrent.

Wow..did I open up a can of worms just by asking a simple question..

Garden nurseries/plant catalogs take advantage of new/inexperienced gardeners and sell them plants that are later invasive. I'm now an OLD gardener and wish I'd made smarter, more informed choices when it comes to perennials. My parents were conscientious gardeners but (they didn't have the Internet) made similar mistakes based on what nurseries told them about plants. I don't regret my choices but will admit some of them were unwise and uninformed. Knowledge is power and power allows us to make informed choices. I have fewer invasives in my garden than my mother did so am less stressed over the legacy I'll leave behind. I also treat invasives to a drink of organic vinegar. It kills them and leaves no dangerous chemicals in the soil.

GG, your response includes information about yourself which is apparently intended to add weight to your opinion. I don't think any better (or worse) of you for being a "degreed horticulturalist".

What I appreciate is critical thought not misplaced dogma. That's what I taught both at university and in high school. I certainly recognized the need for definitions in an academic context and can also appreciate the need for legal definitions about invasive species for legislative purposes.

But we were/are not talking here about "invasive species", but about whether gardeners should be able use the word invasive when talking about their experiences with their plants; I say "be able to", I should add "without being correct by a person like you".

I didn't raise this issue, you did; and I note from GW that it's not the first time you've taken it upon yourself to correct others in this regard.

As far as I'm concerned, invasive can be a useful word in discussing situations like perennials spreading into evergreens or into lawns. Also, in a gardening context, it seems silly to correct people for using the word invasive when they are talking about perennials native to say Europe but raise no offence when they are talking about perennials, behaving in the same way, which are native to North America. I frequently have to deal with species goldenrod and asters invading our flowerbeds and they are native to the area in which I garden.

Re "(defending) a position that really has no substance": If I had talked to my students like that, I would have hoped (at least at a university level) that they would have got up and walked out.

I took my "thug" into one of our local nurseries where one of the employees has a reputation for his botanical knowledge and he didn't hesitate more than a few seconds before he identified as a Tricyrtis. So I went on a google hunt and am as convinced as I can be as a lay person that is is some sort of Tricyrtis.

That said, I can't find a perfect fit for identifying the species. The plant form matches any number of Tricyrtis but the flower itself is a lot harder to pin down. The closest I can come is to a miniature and plainer version of formosanum.

I occasionally see a lone one or two in the bare shady areas at our tiny little local mall which is across the road and a little more from my back yard. My neighbor, who also has it in her garden, has seen it along our local roadsides. . So I have mentally classified this thug as an escaped exotic which I personally could see as potentially invasive because it seems highly prolific in both of our Gardens.

While there is a generally clear and recognised scientific definition of 'invasive species', the concept of native species is a bit more problematical with, to my mind, utterly spurious definitions which are neither clear nor politically neutral. The vague definition of non-native relating to european species introduced sometime during the 17/18C settlement of the USA is...to my mind, just rubbish. A bit like declaring all 'antique roses' were bred or arose naturally before the 1867 introduction of La France. A handy generalised concept but with absolutely zero scientific validity (since the human part in species migration simply cannot be compartmentalised as somehow separate from any other movement of organic material (cells do not recognise borders)...nor can we ignore the concept of adaptation in the mania for some purist stance.

The environmental problems relating to invasive species are recognised, codified and accepted globally...while the increasing mania for 'natives' is essentially a pre-occupation with the USA (and, for somewhat different reasons, Australia). Currently, still only a small percentage of gardeners...but I consider this movement to be pernicious and ideology driven and wait to see how much traction it gains in Europe.

Call me simple minded, but it does not escapemy thinking that one of the other, celebrated examples of 'native' collections, is the Kirschenbosch botanical garden in SA - home of apartheid. I do not welcome these celebrations of nationalistic pride as being in any way useful for humanity....not least because of the fluid nature of life and its resistance to imposed categories of exclusion/inclusion.

caveat - I recognise the willingness to work hand in hand with 'nature' and basic principles behind wishing to maintain a selection of adapted species in a particular habitat - I do it myself in the woods - it would be both ridiculous and unthinkable to introduce a buddleja for example...I just draw the line at the 'purist' position which can shade into intolerance so very easily. Also, this is my personal belief and has no scientific backing or legal meaning...just where I am coming from personally. Not a slur or smear on native gardeners but wanting to engage with this issue which really has not taken hold of the horticultural imagination (yet) over here - although, judging by the rise of the horrible 'pastiche' imaginary settings at Chelsea (A Maltese Gorge ffs), it can't be long in coming.

Echolane - I'm aghast that your 'expert' identified your thug as a Tricyrtis. There are multiple distinguishing features which eliminate that id. Not surprising you couldn't find a match.

I believe it is Epipactis helleborine, a fairly rare British native terrestrial orchid and a nuisance invasive (in the strict botanical sense) alien in N America. It's a frequent visitor on the Name That Plant Forum. E helleborine invasive in SF

Major thugs in my garden: lily of the valley, sweet woodruff, Spanish bluebells, common Muscari, Japanese anemones. I've been fighting with all of them for years. they all swamp, smother and kill more desirable plants. I have had zero trouble with my one Buddleia seeding but I do deadhead it, it's a smaller cultivar. I am constantly pulling up holly and ivy seedlings assume spread by birds as neither are nearby and oxalis is my worst weed.

- I'm aghast that your 'expert' identified your thug as a Tricyrtis. There are multiple distinguishing features which eliminate that id. Not surprising you couldn't find a match.

And I am more than annoyed at my 'expert' and the countless fruitless hours I have spent on the wrong pathway to identifying this noxious fellow! Thank you and thank you again for properly identifying my very unpleasant garden thug as Epipactis helleborine, which I think can now be properly called an invasive. Identifying it has brought me closer to fellow gardeners who suffer as I do from its pernicious characteristics and I no longer feel so alone. .

Browsing turns up numerous unflattering articles and how it frustrates gardeners with its underground network of roots and resistance to pesticides and its prolific wind borne seeds. it has made the New York Times and our local SF Chronicle as an noxious weed, it is listed in Michigan and Wisconsin as an invasive, and so on.

Here's a photo of it in flower. I try to make sure it never flowers in my yard!

Bingo. That's the one! Weirdly it is only just clinging on in its native climes. We could do with it being a bit more robust here.

Campanula, Buddleja introduced itself to my wood. But since it moved into the gap created by the JK eradication programme I let it be. Now sallow is displacing the Buddleja. And ash is moving in on the sallow.

Um, my tiny home garden has a vague attempt at colour schemes...with a 'hot end' nearest my greenhouse. This is actually a small raised bed some 8x4 feet...but I manage to stuff a lot in there...including a small euonymous (I was bullied and nagged about that though) and my temporary placed pots of lilies and dahlias. Anyhow, to keep the show going, in a tiny space means long blooming reliables...and there isn't much less reliable than salvia greggii and...alstroemeria. However, we are in year 2 with the alstros and whilst I have been swooning in glee at the absolutely endless array of sturdy upright scarlet stems, positively awash with bloom power...there is a tiny, niggling feeling that such prolific, exuberant flowering must have some horrid price to pay down the road.

With our climate in winter, Buddleja davidii, planted, last an average of about four years (based on both David Tomlinson's (Merlin's Hollow) and my own experience). They can't survive especially cold winters. But people still want them.

I really want to try Centaurea Montana Bluet...think that's the correct name...anyway, absolutely beautiful flowers and foliage. I saw it in Steamboat Springs CO, so think conditions may be right here in SW Colorado, I just have to keep the soil moist.

Anyway, upon reading up on the plant it is considered invasive in parts of the world. Have any of you had a negative experience with it?

Thanks.

Achanthus is staring to bloom which makes the fight against it worthwhile.

and then there is Goose-necked loosestrife... le sigh. so pretty in bloom, so inclined towards world domination.

susanb92 Centaurea montana is a wonderful cheery plant that is easily controlled by deadheading most of the blooms after flowering but before they set seed.

The chipmunks have been deadheading mine for me before they get a chance to seed. The silvery foliage emerges very early season and they flower for quite some time.

Hi peren.all!

Thanks for the info. I hadn't seen Centaurea Montana before my trip to Steamboat Springs, and am very excited to try it in my garden. I am such a sucker for blue flowers! Now I just have to find a local nursery that has the plants. We only have 3 independent nurseries and one is 50 miles away, so I may resort to mail order.

Thanks again...happy gardening!

I have Epipactis helleborine too. Roundup is ineffective, but I have had some success using Triclopyr herbicide. I apologize to those who are aghast at using a herbicide, but this is very invasive.

A plant that I wouldn't consider as a perenial but it is definitely invasive is Ailanthus altissima aka Tree of Heaven. It is brutal.

I got a free packet of seeds from the woodland trust and was amused to see buckthorn figured prominently in the mix...recalling the agonised battles with this in the US, the mix is still sitting in seedling pots, safe in my back garden.

The plant movements through my wood are a source of continual astonishment to me - this year appears to be burdock in the ascension - huge, huge leaves, dwarfing the 2 hopeful gunneras I planted (tinctoria and manicata). And hovering nearby, dangerously attempting inroads - the horrible phragmites.

Yep, Flora - buddleja has invited itself into my demesne too.

I would add phlox, Joe Pye weed, columbine and Rose of Sharon to the invasive list. You have to be on top of these to prevent reseeding otherwise it spreads everywhere.

Columbine has had a big year in my garden as I see the seedlings everywhere. It is somewhat more obnoxious than other overly enthusiastic seeders because it's tap root makes it hard to pull.

Ct, I see you are a fellow sufferer with Epitactis. What a horrible plant! I just cannot get rid of it in spite of my daily zeal to ferret out every last survivor. The plant likes to hide in the shade canopies of other shrubs, grow through the middle of mounding plants like Geranium, or play peek-a-boo in my grasses, making it hard to spot and more difficult to kill. I suffer no attacks of conscious using chemicals to try to kill this thug.

Here are a couple of photos of my Epipactis helleborines. I use Crossbow herbicide. It's available on Amazon.

I just looked up Crossbow in my zeal to find a good killer of Epitactis and found some interesting info, mainly that it still Roundup, but in much higher concentration, Here's what one customer review said about Crossbow:

Most commercially available Roundup products contain between 1-2% glyphosate. This concentrate is 41%. Once a certain saturation level is reached within the weed, applying more (or stronger) glyphosate will not accelerate its death. It is more effective to treat several times with 2% solution over the course of a month, than to treat once with a stronger solution.

Sinxe I already have a gallon of Roundup concentrate, I can make my own Crossbow in a nearly two to one ratio. Or, maybe I'll just continue treating my thug with repeat doses of lower strength Roundup.

It seems so funny to me that Buddleia Davidii is considered an invasive/garden thug/undesirable in some environments. I killed two huge Buddleia two summers ago not know what they were just by cutting them back too much, or maybe it was winter, but when the one surviving one bloomed last year, I fell in love with it. So this year I've been babying that plant and searching everywhere in my garden for Buddleia seedlings. I think I must have a sterile one?

I guess at the end of the day invasiveness/thugness/undesirableness is in the eye of the beholder?

Yeah, it's very regional as to what is invasive usually. I also can't keep buddleias, don't even try any more. Also in drier areas, purple loosestrife is a good ornamental, but I've seen it taking over entire river flats in wetter cooler climates.

I also tried to grow an Epipactus once...it very quickly died in the heat. So, I have to chuckle at the folks with the orchids coming out of their ears :0

It does seem very evident that which perennials will act invasively (invasive: in both the broad and the narrow sense) depends on the plant's actual growing conditions and that includes a number of variables related to garden location and even sometimes to the practices of individual gardeners.

The irony is that I, and I'm sure Campanula, would love to have Epipactis helleborine in our woods. Sadly it is increasingly rare here in to natural home.

One of the things that mystifies me about Epipactis is its lack of ornamental appeal, therefore why would anyone have wanted to plant them in the first place, or in your case in the UK, welcome more of them.. The flowers are so tiny one almost needs a magnifying glass to see their orchid complexity. To say they are insignificant is almost an overstatement, and what's more they are not even colorful. Perhaps a large clump of them makes an attractive ground cover, something I have not allowed them to display as I've limited them to one stem, or at most two. Of course, my lack of appreciation is perhaps more a statement of my aesthetic shortcomings (!), an inability to appreciate subtle and understated...

In my case, I think it's just because they were a potentially culturable hardy orchid.

Epipactis helleborine is a threatened native species here in the U.K. I can count on the fingers of one hand the times I have been lucky enough to find it. It is also very beautiful if you take the trouble to look at it properly. That is why I mourn it and would like to see more of it. By your criteria we should not concern ourselves at all about the loss of native species unless they are big and obviously showy.