Loyal reader and thoughtful commenter Ray Eckhart posted a while back (something along the lines of) wouldn’t it be nice if we could come to some agreement on all this “what’s invasive” terminology. This has been flitting in and out of my brain but has not found sufficient gray matter to come to rest. Regardless, here goes. I’ve attempted to capture these concepts in as few words as possible. My opinions in no way reflect those of the Garden Professors, blog host Washington State University, or anyone else important, for that matter.
Native. From these here parts.
Or this half/region/corner of the Continent, depending on your definition. And there are LOTS of them. We had this discussion in my Herbaceous Landscape Plants class last week. My students alone came up with 10 different definitions and/or criteria, all probably legit. I teach a plant as native if it is found east of the Mississippi (these are garden plants, it’s not a botany class). I try to describe its “nativeness” more in terms of whatever biome it came from (tall grass prairie, deciduous piedmont forest, etc.) as cue to how to best use it in the landscape. If it’s found even closer to home, I find myself describing it as “really native” which makes no sense, but I can’t seem to stop.
Alien. Not from here (wherever here is).
Is a broader term than “native” because “here” seems to refer to land masses, whether continental or island. Alien has a rather negative and even inter-planetary vibe to it. “Must…thinkofway… to… eliminate… Japanese Privet. Helpme…, Spock.”
Non-native. The kinder, gentler alien.
As in, Hosta are not going to take over the planet. Even though non-native is often used in the same breath as alien, we need it to stand on its own in this case: what do you call a Calochortus (Mariposa Lily) in Virginia? It’s not native to the east coast, but species of the genus are native to the western part of continental North America and further south. So I deem it non-native, but not alien. Maybe “mail-order” should be a category.
Exotic. An attractive but promiscuous alien.
Invasive. Aliens amuck.
Lists are created, but are unfortunately often ignored (see previous post on ligustrum). There are lots of good invasive plant definitions out there. But can native plants ever be invasive? Or are they just “vigorous” or “aggressive”? See below.
Vigorous. This has positive connotations. Holds its own in difficult situations, makes lots more of itself, can share with friends.
Aggressive. See vigorous, but cue theme to Jaws. Makes a WHOLE LOT more of itself. Can share with unsuspecting friends.
Passive-aggressive. Just when you think “I don’t know what all the fuss was about”, BAM you’re pulling out it of every nook and cranny. I can think of many examples – good fodder for a future post.
Based on these definitions, I see a few of our favorite garden natives as aggressive or passive-aggressive. You’re not sure whether to be pleased or perturbed that a delightful, wildlife-friendly native is reseeding all over your garden. Two examples right here in our campus garden: Joe Pye (Eupatorium purpureum) and Cup Plant (Silphium perfoliatum). Completely out of hand.
I am no authority on this stuff, just happy to be part of the conversation. Feel free to agree/disagree. But please be gentle; I’m suffering from a late night of watching the Hokies get splatted by Boise State (invasive Broncos).
16 thoughts on “Defining Your Terms”
I was once infor
med that horsetail could not, by definition, be “invasive” because it is a native plant. None the less, it invaded my garden.
It seems like a bit of a dodge but I actually like (sort of) the definitions set forth in the Federal Executive Order on Invasive Species. They read like legal-ese, which they are, but I like the fact they emphasize ecosystems as the reference point. Of course, that’s also a limitation. How do we define ecosystems? Habitat type or forest cover type might be better but these are not consistently defined for all parts of the country. In any event, we need to get away from geographical definitions; a Michigan native or a Washington native is virtually meaningless. Habitat types in Washington cover everything from rainforest to alpine meadow to sagebrush.
If you follow the definitions in the E.O. on invasive plants, a native cannot be invasive. The question is whether horsetail is native in the garden ecosystem. Of course, we can always opt for ‘weed’ for any plant out of place.
Darn, I forgot to include “weed”. And I agree on the geographic references being less-than useful.
don’t forget we live in space and TIME, spock… at one ‘time’ i believe cycads were native everywhere…
Thanks for the kind words, Holly. Fun game to watch and the castrated chickens almost pulled it out.
I like the idea of introducting “weeds” into the discussion, since it allows for a little subjective evaluation. My favorite definition of a weed is “A plant whose virtues have not yet been discovered.”
Love the ‘mail order’ designation — if it’s good enough for brides, why not plants?! I like the distinction between aggressive and passive-aggressive plants, too.
JD, that always throws a fun wrench into things! Don’t forget the Ginkgo fossils found in North Carolina…
Remember that if you go back far enough in time, human beings are native only in Africa. Everywhere else we are more invasive than any plant could be, and far more threatening to the ecology. Should eradicate ourselves?
Just when I think this blog can’t get any better, you go and put this post up. I was actually laughing in my cubicle while reading it, because much of what it says is similar to how I try to describe the natives vs. non-natives argument. Only you did it much better. Thank you.
Bert, I doubt whether most gardens can be called “garden ecosystems”. After the building a house, what’s left of the yard is a mangled mess. What gets planted there is typically pretty sparce and alien compared to the original ecosystem. Holly, I would love to hear your take on this.
I think Bert’s point about ecosystems has to do with where invasive nonnatives end up – outside one’s garden and into “natural” systems.
John K., you made my day. Thanks for “getting” me! Now get back to work.
I laughed out loud too. I love the passive aggressive definition. Why aren’t you extension again???
I think the first comment by Deirdre brings up a really good point — People use invasive to mean two completely different things: Takes over your yard (which natives and nonnatives do equally well) and takes over natural environments. Lots of things that AREN’T invasive in your yard can be invasive in natural areas — like euonymous alatus, or buddlias. And, I presume, the reverse could be true as well. We need two different words for the two different issues.
Nice to see a discussion that gets beyond the usual native-nonnative dichotomy. When I lived in Australia, it all seemed so simple: a plant or animal was either native or it wasn’t. But then there was that insidious Indo-Malaysian influence in the rainforests and the dingoes and all those peoples that managed to find Australia before Captain Cook. Now that I live in Alberta, were every living thing except a few microbes has invaded in the last 9-10 thousand years since the glaciers melted, ‘native’ seems a very strange and artificial concept. Artifice, of course, brings up another can of worms: ‘natural’. Was there ever some perfect, unchanging, Garden-of–Eden-like, assemblage of plants and animals anywhere?
Check the origin of the word ‘native’ – it is from the Latin for a natural born slave (as opposed to one captured in war, condemned for a crime, etc). This seems appropriate: we generally use ‘native’ for something we feel was enslaved by our cultural perspective to a particular geographic region, biome, etc.