Could someone check on this plant, it may be duplicated in our database as Adiantum aleuticum and A. pendatum. Thanks. Sorry, I have a hard time deciphering the CofL but was using the UW Burke Museum and Consortium of Pacific NW Herbaria sites which seem to show A. aleuticum as the accepted name and A. pendatum as a synonym (if I am reading their information correctly). Thanks.

According to the CoL, both A. aleuticum and A. pedatum are accepted names. There is no A. pendatum, so I'm assuming that's just a typo in your post.

Yes, typo (oopsie). So how can I tell which one to use? If I just somehow guess, I'll go with A. aleuticum as that sounds more PNW-ish to me...and seems to be the preferred name from the Burke Museum, although their information is confusing as well. They list A. aleuticum as the accepted name, A. pedatum (and others) and synonyms, but then list A. pedatum as 'Treated in the Flora of the PNW as' - whatever the heck that might mean.

My field book, Plants of the Pacific NW Coast, lists it as A. pedatum with the notation it is also known as A. aleuticum. I have found this field guide to not always be accurate, though, so usually look for a secondary source when there is a conflict. It was first printed in 1994 and most recently in 2004, not sure if it was updated at that printing or not. Maybe I need to get a more up to date field guide.

Hi Deb-
I had wondered this myself some time ago. In the USDA Plants Database it is listed as A. aleuticum, and also in 'The catalogue of Life" which this website usually uses for taxonomy. They are both useful (I especially like the USDA one which shows distribution of native and naturalized plants, you can even zoom into the county level on the map! Here are links to this fern in those websites. I have bookmarked both websites. Now I am gonna go find the Burke Museum website, which I did not know did anything like this... I see another bookmark coming!

http://www.catalogueoflife.org...
https://plants.usda.gov/core/p...

So I remain confused which name is accurate, A. aleuticum or A. pedatum -- or are they two different plants. In which case, how does one differentiate between the two?

It appears the name which is now accepted is A. aleuticum.

But, according to Zuzu (correct me if I am in error), both names are accepted. So, which?

At this time, they're classified as two different plants, although you can see from this link that some Infraspecific taxa of A. pedatum are now synonyms for A. aleuticum.

http://www.catalogueoflife.org...

Here's the entry for A. pedatum, which has three accepted infraspecific taxa of its own.

http://www.catalogueoflife.org...

They are two different plants, but I don't know enough about ferns to tell you the difference between them.

I don't yet know how they might differentiate from one another, but from reviewing the CofL distribution pattern, A. aleuticum is native to the west coast (Aleutian Islands south to Chihuhua and in some northeastern states (Newfoundland south to Maryland) whereas A. pedatum is more on the east coast, and also in various other countries. There are some overlaps. I also found that the two used to be classified as A. pedatum until 1991 at which time it was determined that A. aleuticum was a separate species. Still digging to try to figure out how one tells the difference other than by location. I'll include what info I find as a comment in both entries.

Both are commonly known as five fingered fern, A. aleuticum is AKA Aleutian or western maidenhair fern, whereas A. pedatum is AKA northern maidenhair fern.

Something new to learn all the time...

@zuzu, I tried to post a query in the Fern forum, but somehow it got posted as a comment (I guess?) under my photo which is in the A. pedatum entry. Can you move this to the fern forum, or should I just delete it and recreate in the forum? I must have done something untoward when I copied my photo into the thread (?) Thanks Deb

I don't have the option to move this thread. I have proposed the deletion of your thread, which ended up in the Plant Photos Forum because you posted it as a comment under your photo, as you suspected. You can post your query in the Fern Forum or the Plant ID Forum.

Thanks, I will do so.

Thanks Deb for investigating this for us all- I am curious to see what you come up with.

Mary, I posted in the Fern forum, hoping someone will come forward with an easy way to differentiate between the two. I'm guessing I have A. aleuticum as apparently A. pedatum does not thrive in the PNW and will often die off. I've had my fern for several years, and even moved it back in 2014. Everything I could find online was a bit too scientific for me to sort out though. I'm hoping for something simple, like counting stamens to differentiate between an azalea and rhodie.