An example of why documenting invasive plants is useful

iNat users generally document whatever interests us. And invasive plants, especially overly common ones, generally aren’t that exciting. But there is often real value in documenting the invasive plants as well.

An example: Ailanthus altissima (Tree-of-Heaven) is a weedy tree native to China, now common in temperate and sub-tropical areas on six continents. Ailanthus is so common in many areas that it is rarely observed. For example, I could see them from the freeway as I drove through Petaluma, California, today, but there are zero observations of them in Petaluma.

Why is this a problem? There is an invasive insect Lycorma delicatula (Spotted Lanternfly) spreading through the USA (thus far no observations in Canada or Mexico) whose primary host is Ailanthus. Lycorma is a serious pest of many plants, most notably grape vines. This becomes a serious environmental problem because most wine-growers are going to spray anything and everything to kill these insects before they let their absurdly valuable grape vines suffer.

The US Department of Agriculture now recommends preemptively removing Ailanthus growing anywhere near grape vines, even if Lycorma has not yet arrived. The economy in the area to the north and east of Petaluma (think Sonoma, Napa) is heavily vineyard focused.

Because we avoid observing the boring invasive plant (which isn’t hard to find, or photograph, or identify), our data provide very little guidance of where it is or isn’t, and therefore can’t be used to guide an environmentally and economically important effort to reduce populations of that invasive plant.

I am not arguing that anyone has a responsibility to observe anything they aren’t interested in. Rather, I am suggesting that there is real (if unpredictable) value in including the invasives among your observations, which I hope will make doing so more interesting. Roughly one fifth of my plant observations are of introduced species, and I try to maintain about that balance.


That type of stuff is my specialty. A lot of it isn’t promptly IDed because it’s boring junk but it’s very easy to ID because it’s the boring junk.

I’m hoping to figure out a way to comfortably have open location for a lot of my observations and when that does happen, I think it’ll show very clearly how bad a lot of the roadside invasive species are in NY. That’s (one of) the long term goal(s), anyway.


I hear you. My parents live in Putnam County, NY. There is Ailanthus growing all along their road, and every road nearby. There must be hundreds of thousands of stems of it within a couple of miles of their house, but zero observations of it within that distance. I will begin to fix this next time I am there.


Brazilian Cat’s-ear is all over town. My observation of it earlier this summer was the first for the county.


I think we’re doing pretty well locally with documenting most invasives. Doing a lot of plant IDs in our county, I feel the most contributions of this nature come from school classes. Not sure if this is actually true and would hold up to scrutiny, or if it’s just stuff other identifiers slap a “plantae” on and move on because they don’t want to waste their time on it so I end up looking at a lot of them. The kids can’t tell yet what’s “exciting” and what is boring and invasive - it’s all new to them and they tend to photograph every dandelion, multilflora rose, and autumn olive they can find.

That said there are apparently only two Ailanthus altissima observations in the county. I’m 100% certain there’s more than that! It has pretty aggressively spread through all of NC. Either they are lingering unidentified in the Needs ID pool, or people aren’t adding observations. (I know I have a picture of one that I still need to process and upload.)


I wish this was this easy. Part of the reason it’s so widespread is because it’s very difficult to remove without systemic herbicides. Most of my work involves spotted lanternfly and tree of heaven, and I honestly sometimes wonder if we’ll ever view SLF as biocontrol of ToH…

Not as much of a problem if you are using the native fungal pesticides I’m studying. :)


couldn’t agree more. Recording invasive plant species is one of the main focuses on most of my walks, I’m currently sitting at 732 species observed for Australia. I also collect a lot of specimens for the NSW Herbarium, focusing especially on rare weeds or new area/state/national records.

A really interesting one I collected recently is this Cyperus papyrus. It’s a huge (~50 m x 20 m), highly dense population, exceeding 3 m height, alongside a road verge on the edge of Casuarina swamp that I’ve known about for a few years but had never got around to collecting a specimen. Looking at old satellite imagery of the area, turns out it’s been there since at least 2010. Looking at old collections from the area, there are some very nearby specimens collected in the 1990s! So possibly the parent plants of this huge patch.


I add observations of invasive species whenever I can. However, there’s often too many for me to photograph, list and upload. But all in all, I’ve seen it as essential to add observations of invasive species to give an idea of how common and widespread they are.


Thanks for bringing this up, well said and always important!

Speaking of, for people in LA and Ventura County who visit the Santa Monica Mountains, we have a project designed for exactly this! Our botany crew is currently wrapping up the annual invasive monitoring program that is seeking out 25 target species – those we still have hope to be rid of. Check out the invasives if you’re in the area, including that pesky Ailanthus altissima.


I also think it very valuable to document invasive species when I encounter them, though as someone else mentioned, it sadly is so often that my few observations don’t accurately represent the actual presence. Ailanthus has been on my radar for several years now, and I do try to make observations often in case there are any agencies who might be interested to go after them. I tried locally on my street, but it is a losing battle when, after I controlled some in a common area with herbicide, someone went and dumped a huge branch full of thousands of seeds right there. It had fallen from a tree in their yard and they dragged it over. I almost cried, and I have given up. I’m renting, anyway.

This is why Ailanthus is so difficult to get rid of:

This shows a new seedling. I had to keep digging to make sure I got all the root sections, which break very easily to leave pieces of themselves. I have been fighting them in my dad’s yard for years, and we learned that you can’t just pull a tiny one. It will always come back. Unfortunately the neighbor has mature trees and saplings, and does nothing about them.

This shows a small but established one that I dug up with a spade, again trying to make sure I got it all. You can see that this one has been there a while, roots no longer brittle and white, but orange and strong and extensive. Only the tiny top portion was showing above ground, barely noticeable:

Unfortunately I do not believe SLF will control ToH. The trees come back if you whack their entire top portions off, so some leaf damage doesn’t impact them. Ailanthus Webworm Moths appear to be doing some serious damage to a few saplings here, but despite the apparent devastation, I’m sure they will recover once the caterpillars have moved on:

I have been watching these trees spread for years now with feelings of dismay. I wish some real control could be found for them, but until then, I’ll continue to document so people know where to concentrate when they figure it out.


I’ve begun using iNat to inventory invasives on my property in western NC, which I hope adds the additional value of having it on public record. One issue I’ve noticed is that my IDs are not confirmed by the wider community, I suspect due to the “boringness” attributed in the OP.

In the process, I’ve begun to notice occurrences of Mimosa/Silktree (Albizia julibrissin) in the area, but not tagging due to the same bias. I wonder if its worth creating regional projects to catalog those listed? Perhaps they already exist?

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I will take a look when I have a chance, and verify those I know. Albizia is really bad in Chattanooga where I am currently visiting my dad, and in my back yard at home because my landlady invited one in, so I have to keep pulling seedlings, and in the neighborhood at large. Good luck with that one!

This project exists for DC:

I’m not sure about others elsewhere.


For people in NY, you can upload observations of invasive species to NY iMapInvasives. They were asking people to upload their observations of tree of heaven in July.

There are also a few other jurisdictions that participate:


The Queen Palm (Syagrus romanzoffiana) is described by Wikipedia as " widely planted throughout much of Florida and other parts of the southern United States, although it is not yet widely established in the flora as of 2000." Well, it may not be “widely” established, but “widely” is a qualifier.

Here is a map of iNat observations of the species in the north San Francisco Bay area and surrounds:
As you can see, most of the squares are blue, indicating captive/cultivated. But what do you notice about the American Canyon/Vallejo area? A couple of purple squares and even a red one.

The map pin shows my observation of the species:
Queen Palm (Syagrus romanzoffiana) from American Canyon, CA 94503, USA on April 17, 2020 at 10:20 AM by Jason Hernandez. Five naturalizing seedlings on a streambank. I have included one photo of each. · iNaturalist

In the following year, I found additional seedlings in the same area, a few meters further down. It makes me wonder whether the Wikipedia statement of “not yet widely established” will one day need to be removed.


We have a project

I joined this one - which notifies people of what and where to remove


SLF feed on fluids from the tree, not the leaves. Our regular sampling sites from some of the earlier establishments are having population crashes of SLF because they’re killing the ToH. Sustained feeding for several years seems to be sucking them dry. And now the ambrosia beetles are moving in! Who knows what this will do long-term, but it definitely wasn’t expected.


Agreed, I’m from SE PA (though only go back to visit now), and SLF puts a hurting on TOH. If you stand underneath an infested one, you will be coated with honeydew (well…) in a matter of minutes. Even if SLF doesn’t kill TOH outright, it still reduces growth and reproduction which is a type of control. Biocontrol often does not make a target species extinct/extirpated, but in the context of invasives, reduces their spread/makes them less invasive.


Except for the fact that we don’t want the SLF, that’s great news! Since it seems there’s no putting that genie back in the bottle, maybe it will have one positive side effect. Thanks!


It would be very helpful if people would NOT mark alien species automatically as [Captive/Planted] exactly to show that they might be invasive!


Agreed. In my area (New Mexico), Russian Sage (Salvia yangii) is a popular xeriscape plant but it’s starting to show up in a few places where it was clearly not planted. However, these records of likely escapees are typically automatically marked as cultivated in the DQA by the iNat system and/or by reviewers. Adding notes to indicate the context of the record can be helpful even if often ignored.