Native, introduced, or both?

General
1

I am working on restoring montane meadows gazed by sheep and cattle in the Sierra Nevada of California, and just got back from fieldwork where I collected specimens of grasses. I found what I keyed out as a specimen of Swamp meadow bluegrass (Poa palustris), which I do not find much at all, yet iNaturlist labeled it as invasive with a red explanation point symbol. Clicking on the symbol, a pop-up window gave a very specific label, but with no reference or source.

Screen Shot 2026-05-25 at 8.53.45 AM
Screen Shot 2026-05-25 at 8.53.45 AM1574Ă—402 80.1 KB

https://www.inaturalist.org/observations/363224447

I hardly ever find this grass, it seems rare in the area, so I was surprised to see this label. It acted more like a relict native grass found growing by rocks where livestock have a harder time grazing it down. It did not appear to act like an invasive across this meadow. The livestock have been removed on these public lands so we are trying to inventory the meadows to see how best to restore them to diversify native species which have been heavily impacted by grazing.

The Manual of Grasses of the United States (Dover 1971 edition) by A. S. Hitchcock and Agnes Chase treats this species as native to North America, and specifically to Sierra Valley (north of my study site), and Siskiyou County in California.

I did a little more investigation online and got mixed results.

US Department of Agriculture says it is native: https://plants.sc.egov.usda.gov/plant-profile/POPA2

Calflora says it is non-native to CA: https://www.calflora.org/app/taxon?crn=6683

Jepson eFlora gives no indication of status: https://ucjeps.berkeley.edu/eflora/eflora_display.php?tid=38863

Interestingly, the most detailed discussion was in Flora of North America: https://floranorthamerica.org/Poa_palustris

"Poa palustris** is native to boreal regions of northern Eurasia and North America, and is widespread in cool-temperate and boreal riparian and upland areas. European plants have also been introduced to other parts of North America.** Plants in the Pacific Northwest and the southern United States are usually regarded as introduced, but some populations may be native. Poa palustris is used for soil stabilization and waterfowl feed."

So conceivably there could be naturalized stains here but also relict native populations that might need conservation. Until we do a wider genetic study we may never know, but no one I know is working on this locally. So I would like to err on the side of protecting these meadow grasses.

I may ask for a Feature on iNat where the status label is not automatic with regard to naturalized status, because sometimes this is a complex situation.

Any thoughts on how to clarify this? Thank you.

2

Turning on the Bat Signal for @sedgequeen! I always appreciate your deep expertise and your dedication to helping others on the iNat Forum!

3

If you click on the “status” tab on the Poa palustris page it lists all the Establishment Means that have been added for the species. It’s been labeled as “Introduced” in California, as well as Oregon and a bunch of individual California counties, including Mono. The Establishment Means can be changed, removed, or added by users on this page. There is now a History feature where you can see who changed/added these Establishment Means and what their reasoning was, but in this case these were added before the History function was introduced, so we have no idea who added them and why. It can be changed right here if you have reason to change it:

swamp
swamp816Ă—456 63.6 KB

In any case, it’s already true that “the status label is not automatic with regard to naturalized status”; someone had to add that Establishment Means manually at some point, but it was so long ago I don’t think we know why they did it.

4

It might be worth checking commercial variants and hybrids. These are often not in the keys as they don’t have a (separate) scientific name.

5

I just want to point out that the pink/red (!) symbol stands for introduced and not necessarily invasive.

Scientific understanding of how various species arrived in a region is changing all the time. Stinging nettles were considered “introduced” in North America for hundreds of years because at some point early naturalists who believed they were all the same species assumed they came from Europe. In recent years, it was discovered that most of the stinging nettles found here are a separate species indemic to North America. Good thing we didn’t wipe them out!

Unless a plant is actually a problem invasive - believed to be introduced by humans and aggressively crowding out native species - I think it’s best to err on the side of caution, and leave it be.

6

For difficult Poa questions, the only reliable source is Dr. Robert Soreng, a researcher at the Smithsonian, who most of us consider the bluegrass god. I’ll try to see if he has further comments on this question, but here is what he wrote for Flora of North America. It won’t really make you happy.

"Poa palustris is native to boreal regions of northern Eurasia and North America, and is widespread in cool-temperate and boreal riparian and upland areas. European plants have also been introduced to other parts of North America. Plants in the Pacific Northwest and the southern United States are usually regarded as introduced, but some populations may be native. Poa palustris is used for soil stabilization and waterfowl feed."

7

“some populations may be native” is what I was referring to and that piqued my interest. A similar problem occurs with populations of Poa pratensis, which may have some native populations mixed with introduced populations.

My question was more about how we should deal with a label on status that we disagree with and is too broad, does not take into account complexity of populations of a taxon.

8

My question stands. Whether introduced, invasive, or other status, how do we deal with this all-too-general label when some populations of the species may in fact be native?

9

Thank you very much, that is very helpful!

Maybe I should ask to have a “both native and introduced populations potential” feature added to this list.

10

Thank you Adam!

11

As far as dealing with it on iNat, I think it’s very reasonable to change the status to “unknown” on the basis of different authoritative sources giving conflicting answers.

12

Exactly, do this and provide a comment with a source (and maybe a link to this discussion)

13

Regarding the supposed native North American form of Poa pratensis: The necessary lab work confirm that it’s relatively distant from the European forms hasn’t been done. It’s an unconfirmed hypothesis, so far.

14

That’s my point–no one has done an extensive study of these populations, so better to err on the side of caution when labeling everything introduced. There may be some native populations too, no one knows.

15

Thanks everyone for the ideas on how to deal with this. Much appreciated.