I think "invasive" is a relative term. I tend to feel that not much is invasive in zone 4! (Maybe purple loosetrife and garlic mustard). Even creeping charlie has a place for some people/some situations. In fact, I look for what are often called invasive plants. At least they'll have a chance in my high pH, clay, shade, frigid north garden.

To me "invasive" doesn't mean simply that the clump increases in size rapidly, but that the plant sends out runners and roots a long way from the original clump...like gooseneck loose strife....which is the personification of invasive to me.
Feverfew is not invasive, it seeds freely and is easy to pull out, hemerocalis fulva is invasive because you can never really dig it all out.
And I don't know for sure what kind of campanula it is that is all into everything in my garden, because it hasn't bloomed in more than 10 years.....I pull it out constantly and I dug bushels of roots, before it came to rest in the middle of clumps of other flowers....that's invasive!
Bean, I'll dig out some roots and sent it to ya if you want to see first hand invasive.
Linda C

Certainly factual information is much better then using the catch all word "invasive." The issue comes from the fact that what may quadruple in size and send out runners in a certain zone with certain soil, may not do that in your zone/soil. And, what most of us are really interested in, is not specifically what it might be doing in someone's garden, but whether it might have the possibility of taking over our garden. From my point of view, once a plant is shown to be invasive somewhere, it is on the "do not plant" list for my yard.

Yeah, it gets thrown around a lot. I grow plants that are considered invasive. Obedient Plant, Gooseneck loosestrife, anemone robustissima to name a few. Just got done battling the anemone. It had run all over, under a carpet rose..you get the picture. Wasn't the plant's fault, though..it was mine for putting it in the wrong place. What is invasive to someone with a small town lot, might be something that would just make a nice sized mass in one of my large beds. It's all relative, I guess. When I read "invasive", it just means to keep an eye on it, to me. What I consider invasive are plants that actually do harm to the ecosystem, say....kudzu.
Linda, maybe you have Campanula Takesmania (sp) Korean Bellflower. I don't think I've ever seen anything take off and cover real estate like that plant. I got rid of it before it got too carried away. Might be a great choice for somewhere, I just don't happen to garden that particular area ;) Kinda like purple and orange plaid wallpaper...I'm sure it's lovely in the right room, I just don't have that room!
Brenda

I agree that the term invasive is overused and vague. But if a plant spreads by runners or self seeds everywhere, I want to know before I plant it. I planted campanula takesimana "Bellringers" a couple years ago and it spreads by runners and it seems that if you leave just a little piece of root behind it resprouts. I wouldn't have planted it if I'd known how far it would spread and how hard it would be to get rid of.

Juliet

Consider these as more specific definitions:

Invasive: Spreads a far distance away, as in miles away from the parent plants, via seeds (often carried by birds) or plant pieces transported down the river/stream/etc.

Aggressive: Spreads rapidly but only locally, in the garden it was planted.

Example:
In the PNW, English ivy is both aggressive (spreads from one garden into an adjacent one via stems) and invasive when spread by bird-dropped seeds along with a packet of "fertilizer."

Yes, I agree. Jean is right! I think we tend to use the word 'invasive' when we really mean 'aggressive.' Think of invaders as being aliens. They don't belong here! My European Buckthorn is an alien invader - it's just a matter of time until I call in the armed forces...

I think plants are invasive if they get out of control REGARDLESS of the growing conditions. I planted goosenecks in heavy clay thinking that would contain them and 3 years after I removed them from the bed (because they were everywhere) I still find "babies" in the Spring. I would certainly call that invasive. Plants that spread but respond to easy controls (root barriers or being tidied up a couple times per growing season) I wouldn't call invasive.

Jean - when people here use "invasive", they are usually describing what you call "aggressive." Unfortunately, most don't have the macro view about what this plant is going to do to their community; they just care about what it's going to so to the bed they plant it in.

No I don't think the word is overused, but perhaps it is used improperly. Invasive species are a very serious problem that threaten natural habitats all over the world. I've read that invasive species are the 2nd biggest threat to the survival of native species in North America, after development and habitat loss.

I think "invasive" has a very specific meaning. An invasive species is a non-native species that is living outside of its native habitat and competes so aggressively that it displaces the native species and thus disrupts the ecological balance of the non-native habitat.

I'm pretty sure that this applies to a species in a wild environment, not a garden environment. Nor does it describe a garden plant that is a vigorous grower (unless that plant has already been determined to be invasive in the wild).

Invasive can be applied to flora or fauna species; also, a Eurasian species can be invasive in North America, and vice versa, a North American species can be invasive in Europe or Asia.

Hi,

I feel this word is overused, and in the wrong way. Plants that are considered "invasive" such as Vinca, Ajuga, Obedient plant etc are large plants at maturity that are grown for the purpose of filling lots of space in a small amount of time. If you want a quick growing groundcover plant something that will do just that. Plants are too often planted in the wrong area and called "invasive."

Jen

I think it's both overused and also used incorrectly. I don't like people to just cough up the term loosely and label a plant as such, because it might influence somebody else who would find it a perfect plant for their situation.

At least they are using the proper word for their intentions. I go crackers when I hear people using the word evasive when referring to plant material. It's hard to stifle the giggles. It brings up such vivid mind pictures. Ditto when people call perennials anything but perennial. I have heard many different variations on that theme as well. Often they ask for pre-annuals, but the best one yet was last week from a woman talking about her perineals. I'm sorry, I was a nurse in a previous life and I don't think she knew the definition of that word.

I suppose most people use the word "invasive" loosely, but my understanding is that it has a pretty clear meaning in scientific circles.

Here is the definition according to Wikipedia:

"A species is regarded as invasive if it has been introduced by human action to a location, area, or region where it did not previously occur naturally (i.e., is not native), becomes capable of establishing a breeding population in the new location without further intervention by humans, and becomes a pest in the new location, threatening the local biodiversity."

And the reason I don't think the word is overused is because invasive species are a major threat to native ecosystems, and it's good that people are becoming aware of this phenomenom and talking about it.

I agree that the term is used a lot, but the world has gotten so small that the problem has gotten huge. Invasive plants can wipe out native species and habitats. I used to work for a noxious weed board on the west coast. Some plants that are illegal there are sold in nurseries in my area. It took a while to get over my shock when we first moved here. Most states have weed boards that try to educate the public(many have websites)but not all states enforce eradication. Once you have a solid acre or more of say, Japanese Knotweed, or Purple Loosestrife filling in your lakefront, you come to understand the term "invasive". An example of an invasive species in zone 4 is Knapweed. There is so much of it, people think it is a native...and beekeepers love it. Another is Asian Honeysuckle. One of the reasons these plants are so rampant is because they are not in their native area where there would be natural controls(animals and insects). Most of them have escaped gardens, but some were brought in by the government for erosion control and highway buffers, as in Scotchbroom(the plant that ate the west coast!). The DNR in many states tries to keep these species under control, but they definitely need the help of the public. I'm not meaning to rant, just share a little info :)

calliope said,

"I go crackers when I hear people using the word evasive when referring to plant material. It's hard to stifle the giggles. It brings up such vivid mind pictures. Ditto when people call perennials anything but perennial. I have heard many different variations on that theme as well. Often they ask for pre-annuals, but the best one yet was last week from a woman talking about her perineals. I'm sorry, I was a nurse in a previous life and I don't think she knew the definition of that word."

Bwa ha ha ha! Calliope, you're a poster after my own heart! I sometimes see that spelling of "perennials" on posts here, and I snicker to myself every time.

I've not heard someone use "evasive" for an eagerly-growing plant, but tomorrow when I go out again to weed I'll be thinking just that!

Terrene's definition of the term "invasive" is right on the money. It refers to non-native plants that spread outside of areas where they are originally planted, out-competing native plants and altering the natural habitat.

Using it to describe plants that may spread faster than you'd like in the garden, without threatening the natural environment, is incorrect and tends to downplay the seriousness of the issue of invasive plants through overuse.

Bean Counter,

I agree with you.

After 3 years of coddling and coaxing my "invasive" trumpet vine and burning bush to grow, they both succumbed to the zone 3/4 winter.

You're right of course. I did not mean to downplay the seriousness of true invasives. Kudzu, garlic mustard, those are invasive, over running acre after acre and killing native plants.

Most of the talk of invasive on this forum deals with common perennials. Folks have labeled phlox, rudbeckia, even coneflower invasive. I just wondered if facts would not be better than dire warnings.

I think you're right too Bean counter, that invasiveness is relative even with plants that have been determined to be true invasives.

Burning bush is banned here in Mass. and it is very invasive in my yard, but it may be on the edge of hardiness where Hoghaven lives, so it would not become invasive there.

Apparently, Buddleia is invasive in some regions of the US and is banned in WA and OR. But here in zone 5, it is on the edge of hardiness. I usually put extra mulch around them in the fall, and if we have a severe winter, many people lose their Butterfly bushes. It has never even seeded in my garden, let alone spread beyond my garden and establish itself in the wild.

On one end of the spectrum you have people who avoid any plant that self-sows or otherwise propagates itself by any means other than (maybe) slow radial enlargement of the clump. These are termed "invasive" and the horrified gardener runs for the Preen or Roundup.

Another misuse of "invasive" involves those who have seen a list of plants to avoid or had experience with something undesirable in their area, and go on the warpath when they hear such a plant mentioned in any gardening context whatsoever, even if it barely survives in another location (much less spreads uncontrollably).

Complicating things are plants that can be both aggressive in the garden and invasive in the wider environment. So we just need to think before making conclusions about how a plant will behave in a given situation.